Does the brain control muscles or movements?

One of the major scientific questions about the brain is how it can translate the simple intent to perform an action—say, reach for a glass—into the dynamic, coordinated symphony of muscle movements required for that action. The neural instructions for such actions originate in the brain’s primary motor cortex, and the puzzle has been whether the neurons in this region encode the details of individual muscle activities or the high-level commands that govern kinetics—the direction and velocity of desired movements.

Now, Robert Ajemian and his colleagues, analyzing muscle function in monkeys, have created a mathematical model that captures the control characteristics of the motor cortex. It enabled the researchers to better sort out the “muscles-or-movement” question.

The researchers described their model in an article in the May 8, 2008, issue of the journal Neuron, published by Cell Press.

Researchers have been thwarted in their efforts to measure and model the neural control of complex motions because muscle forces and positions constantly change during such motions. Also, the position sensors, called proprioceptors, in joints and muscles feed back constantly changing signals to the neurons of the motor cortex.

Ajemian and colleagues overcame these complexities by simplifying the experimental design. Rather than asking monkeys to carry out complex movements, they trained the animals to push on a joystick in different, specified ways to move a cursor on a screen to a desired target. This use of isometric force greatly simplified the measurements the researchers needed to make to define muscle and joint action.

As the monkeys carried out the isometric tasks, the researchers analyzed the patterns of muscle activations that corresponded with the isometric forces in different directions and at different postures. They then developed a model that enabled them to test hypotheses about the relationship between neuronal activity that they measured in the animals’ motor cortex and the resulting actions.

They said that their “joint torque model can be tested at the resolution of single cells, a level of resolution that, to our knowledge, has not been attained previously.”

They concluded that their model “suggests that neurons in the motor cortex do encode the kinetics of motor behavior.”

“This model represents a significant advance, because it is strikingly successful in accounting for the way that the responses of individual [primary motor cortex] neurons vary with posture and force direction,” commented Bijan Pesaran and Anthony Movshon in a preview of the article in the same issue of Neuron.

“The results of Ajemian et al’s analysis provide strong evidence that it is useful to think of the output of [primary motor cortex] neurons in terms of their influence on muscles. Their model, in effect, defines a ‘projection field’ for each [primary motor cortex] neuron that maps its output into a particular pattern of muscle actions.”

Pesaran and Movshon commented that “perhaps we should set aside the somewhat artificial dichotomy between muscles and movements, between the purpose and its functional basis, and recognize that the activation pattern of motor cortex neurons does two things—it specifies for the peripheral motor system both what to do and how to do it.”

Alfredo

Neuroscience. 2008 Feb 29 [Epub ahead of print]

The neuron-level phenomena underlying cognition and consciousness: Synaptic
activity and the action potential.

Cook ND.

Department of Informatics, Kansai University, Takatsuki, Osaka 569-1089, Japan.

An unusual property of the neuron is its capability for cell-to-cell
communication via synapses, known to be the neuron-level “protophenomenon”
underlying the brain-level “real phenomenon” of cognition. The temporal
synchronization of such synaptic activity is the leading candidate for explaining
“cognitive binding” and therefore the unity of mind. An equally-unusual property
of the neuron is the action potential, the means by which the neuron sends a
signal down the axon. Although infrequently noted by researchers in relation to
consciousness, signal propagation within the neuron entails the momentary
permeability of the neuronal membrane, allowing a massive influx of charged ions
into the cellular interior. Such openness to the extracellular world is arguably
the protophenomenon of neuronal “sentience,” literally, feeling the charge-state
of the electrochemical environment. Sensitivity to the external pH is a common
feature of all living cells, but is greatly amplified during the neuron’s action
potential. Synchronization of the action potentials of the same neurons that are
involved in cognitive binding is the likely mechanism by which the sentience of
individual neurons is coordinated into the brain-level phenomenon of subjective
awareness. I conclude that a proper understanding of the permeability of the
neuronal membrane during the action potential is as important for consciousness
studies as is a proper understanding of synaptic transmission for the explication
of the cognition made possible by neurons.
PMID: 18406536

I have the pleasure to announce that Dr. Bernard Baars will join this group soon. He will be helping us in the process of constructing the science of consciousness.
Dr. Baars biography can be found at Wiki
Briefly, he has been doing original work, supporting, editing and leading scientific research on consciousness for more than 20 years.
With his leadership, I hope that our Forums will cover the hottest topics in current scientific investigation of cognition and consciousness, with the participation of (more) top scientists in this area.
I will begin this new phase forwarding to the group some important e-mail discussions that I had with Dr. Baars recently – please check our new Forums!

Best Regards

Alfredo Pereira Jr.

Medical Magnetism

Pulses sent into the brain provide a wave of relief for such ailments as depression and migraines

By David Kohn – Sun reporter

April 10, 2008

Sixteen years ago, Steve Zatuchni was a computer sales manager, making a six-figure income. Then all hell broke loose in his brain.

He became severely depressed, to the point that he could no longer work. He slept up to 18 hours a day, and when he was awake, felt so miserable he wished he were asleep. He tried dozens of medicines, in myriad combinations. Nothing worked. Distraught, he tried to kill himself several times.

Then, in 2004, he enrolled in a study of an experimental therapy called transcranial magnetic stimulation, or TMS —a noninvasive treatment that sends magnetic pulses into the brain.

It worked. “Within a week, the depression was lifting,” he says. “Within two months, it was gone. TMS saved my life.” Zatuchni, 59, who lives in the Philadelphia area, no longer takes any medicine.

Stories like Zatuchni’s are no surprise to a growing group of researchers, therapists and entrepreneurs. Proponents—including scientists at Harvard, Yale and UCLA —say TMS could transform treatment for depression as well as a range of other ailments, including schizophrenia, migraines, insomnia, epilepsy, chronic pain and Parkinson’s.

“It’s extremely promising,” says Dr. Abraham Zangen, a TMS expert who does research at the Weizmann Institute in Tel Aviv, Israel. “TMS could revolutionize psychiatry. It’s a completely new approach.”

Meanwhile, over the past two decades, hundreds of small studies have found TMS both safe and effective. Among them:

• Yale researchers reported that TMS can eliminate auditory hallucinations suffered by many schizophrenia patients.

• Harvard scientists have shown that the treatment can reduce what was thought to be intractable chronic pain.

• A team at Columbia University used TMS to improve memory in people suffering from sleep deprivation.

Although TMS is already used in several countries, including Germany and Canada, it is not yet approved in the United States. But that could change later this year if the Food and Drug Administration decides to allow it as a treatment for migraines.

Early last year, in response to an application from a TMS device maker, an FDA panel decided the treatment was safe, but didn’t work better than a placebo. The company, Neuronetics Inc. of Malvern, Pa., plans to reapply later this year.

Maryland inventor Robert Fischell has put his efforts into a hand-held TMS unit (most are currently the size of a desktop computer). The device is undergoing a clinical trial for migraine treatment.

“With a little luck, it’ll be on the market by the end of the year,” says Fischell, who also started a company, called Neuralieve, to produce it.

Fischell, a former Johns Hopkins physics professor who lives in Howard County, has invented dozens of medical devices over the past 40 years—including the rechargeable pacemaker, implantable insulin pump and a variety of stents to help unclog coronary arteries.

He says that in most cases his new invention can relieve a migraine with just two magnetic pulses delivered over a few seconds. “It says, ‘Neurons, whatever you’re doing, stop it,’” Fischell says.

In November, a nationwide trial sponsored by Neuronetics found that TMS improved depression in a significant number of subjects. (Zatuchni was part of this research.)

In the study, chronically depressed subjects received TMS for 35 minutes a day, five days a week, for four to six weeks. Depression improved significantly in a quarter of the volunteers—double the rate of a control group that had a sham TMS treatment (subjects were hooked up to the TMS device but didn’t receive magnetic waves).

Dr. John O’Reardon, an associate professor of psychiatry at the University of Pennsylvania and lead researcher in the study, says the 1-in-4 success rate is actually quite good, given that the subjects suffered from “treatment-resistant depression,” i.e. they had tried many medicines and therapies without success.

“These are the toughest patients to treat,” he said. “This was a significant improvement.” He notes that once the control group was also given TMS, the success rate shot up to almost half of all subjects.

TMS was developed in the mid-1980s as a research tool to help scientists understand how the brain works. It uses magnets to generate a powerful field, creating an electric current that alters brain waves. Scientists soon realized that many patients in TMS studies seemed to improve, and increasingly researchers have focused on its therapeutic potential.

It is not entirely clear how TMS works, in depression or any other ailment. Researchers know the treatment can change electrical activity in targeted brain regions; low-frequency magnetic waves decrease neuronal firing, while high-frequency waves increase it.

In depression, researchers have focused on the left prefrontal cortex, a part of the brain that plays a large role in regulating emotion and memory. Treatment involves sending high-frequency waves into this area, on the upper left forehead.

In the migraine study, subjects place the 3-pound device at the back of the head when they feel a headache beginning. The press of a button sends two high-frequency waves into the brain. The lead investigator in the trial, Richard Lipton, a neurologist at Albert Einstein College of Medicine in the Bronx, says the pulses act as a kind of “reset” switch that stops the electrical storm causing the migraine.

If the FDA does give approval, TMS could change the treatment landscape. Lipton estimates that “millions” of migraine sufferers—there are 35 million in the U.S. —could eventually use the Neuralieve device.

Psychiatrist Scott Aaronson, director of research at the Sheppard and Enoch Pratt Hospital, estimates that a third of depression patients don’t improve with current therapies—and may be helped by TMS.

“We’re likely to be able to treat people we haven’t been able to help before,” says Aaronson, who was one of the investigators in the Neuronetics trial.

Most depression patients are treated with drugs such as Prozac or Effexor; these medicines often don’t work, and more than half of patients taking them suffer serious side effects, including drowsiness, weight gain and loss of libido.

For those who don’t improve or can’t tolerate the drugs, there are a variety of treatments that directly target the brain. The most effective is electroconvulsive therapy, or ECT, which works about two-thirds of the time. Although ECT is much safer than it was in its heyday 60 years ago, it still poses real risks—particularly short-term memory loss.

Two other electrical therapies are sometimes used: DBS (for deep brain stimulation) and VNS (for vagus nerve stimulation). Both require surgery for permanent implantation of electrodes.

TMS, by contrast, is noninvasive and has almost no side effects. Some patients feel an uncomfortable tingling in their scalp during the first few sessions, O’Reardon says. But because it stimulates a specific brain area rather than the whole body, as drugs do, or the whole brain, as ECT does, TMS has far fewer unintended consequences.

TMS does have disadvantages. It is expensive: A round of treatment typically runs between $5,000 and $7,000. Even if the FDA approves it, insurance companies may be reluctant to cover the cost. And it can take time: an hour a day for several weeks for treatment of depression. Some worry that the improvements produced by TMS may not last more than a few days or weeks.

But many researchers—and patients like Zatuchni—say TMS patients may need repeated treatment to keep brain circuits working properly.

Zatuchni goes for such sessions every two weeks, which, he says, keep him stable and happy. Since his TMS treatment began, he has begun work on two novels; he’s almost finished one and has hooked up with an agent.

“I just wish I had gotten it 15 years ago.”

david.kohn@baltsun.com

Copyright © 2008, The Baltimore Sun

1: Curr Opin Neurol. 2007 Dec;20(6):643-9.

Brain-computer interfaces in the continuum of consciousness.

Kübler A, Kotchoubey B.

Institute of Medical Psychology and Behavioural Neurobiology, University of
Tübingen, Tübingen, Germany. andrea.kuebler@uni-tuebinger.de

PURPOSE OF REVIEW: To summarize recent developments and look at important future
aspects of brain-computer interfaces. RECENT FINDINGS: Recent brain-computer
interface studies are largely targeted at helping severely or even completely
paralysed patients. The former are only able to communicate yes or no via a
single muscle twitch, and the latter are totally nonresponsive. Such patients can
control brain-computer interfaces and use them to select letters, words or items
on a computer screen, for neuroprosthesis control or for surfing the Internet.
This condition of motor paralysis, in which cognition and consciousness appear to
be unaffected, is traditionally opposed to nonresponsiveness due to disorders of
consciousness. Although these groups of patients may appear to be very alike,
numerous transition states between them are demonstrated by recent studies.
SUMMARY: All nonresponsive patients can be regarded on a continuum of
consciousness which may vary even within short time periods. As overt behaviour
is lacking, cognitive functions in such patients can only be investigated using
neurophysiological methods. We suggest that brain-computer interfaces may provide
a new tool to investigate cognition in disorders of consciousness, and propose a
hierarchical procedure entailing passive stimulation, active instructions,
volitional paradigms, and brain-computer interface operation.

Publication Types: Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov’t

PMID: 17992083 [PubMed – in process]

2: Curr Opin Neurol. 2007 Dec;20(6):632-7.

Functional MRI in disorders of consciousness: advantages and limitations.

Owen AM, Coleman MR.

MRC Cognition and Brain Sciences Unit, Cambridge, UK.
adrian.owen@mrc-cbu.cam.ac.uk

PURPOSE OF REVIEW: We discuss recent developments in the use of neuroimaging and,
in particular, functional MRI, in the assessment of patients diagnosed as
vegetative state or minimally conscious state. RECENT FINDINGS: In the last year,
there has been a substantial increase in the number of research studies published
which have used state-of-the-art neuroimaging methods to assess residual
cognitive functioning in patients diagnosed with disorders of consciousness. Work
using functional MRI has demonstrated aspects of retained speech processing,
emotional processing, comprehension and even conscious awareness in a small
number of patients behaviourally meeting the criteria defining the vegetative and
minimally conscious states. SUMMARY: The assessment of patients with disorders of
consciousness relies heavily upon the subjective and consequently fallible
interpretation of observed behaviour. Recent studies have demonstrated an
important role for functional MRI in the identification of residual cognitive
function in these patients. Such studies may be particularly useful when there is
concern about the accuracy of the diagnosis and the possibility that residual
cognitive function has remained undetected. In our opinion, the future use of
functional MRI will substantially increase our understanding of disorders of
consciousness following severe brain injury.

PMID: 17992081 [PubMed – in process]

3: Curr Opin Neurol. 2007 Dec;20(6):627-31.

Exploring impaired consciousness: the MRI approach.

Galanaud D, Naccache L, Puybasset L.

Department of Neuroradiology, University of Paris VI, Pierre et Marie Curie,
Pitié-Salpêtrière Hospital, Paris, France. galanaud@dat.org

PURPOSE OF REVIEW: To summarize the application of advanced MRI sequences such as
magnetic resonance spectroscopy, diffusion tensor imaging and functional MRI for
the evaluation of patients with altered consciousness. RECENT FINDINGS: Magnetic
resonance spectroscopy, volumetry and diffusion tensor imaging have shown
promising results in the evaluation of traumatic or anoxo-ischaemic brain lesions
and can detect damage of the brainstem, basal ganglia and white matter tracts not
visible on conventional sequences. A diffusion tensor imaging study has raised
the possibility of detecting ongoing axonal regrowth many years after the initial
injury in minimally conscious patients. Functional MRI studies have shown that a
high level of brain activities, such as recognizing one’s own name or imagining
playing tennis, can be preserved in vegetative patients. SUMMARY: The development
of quantitative imaging could lead to a more objective evaluation of the extent
of destruction or preservation of critical brain areas at the acute phase of
brain injury, which could be integrated in multi-parametric decisional strategies
for these patients. Functional imaging could help define borders between the
various levels of altered consciousness and detect the presence of cryptic
residual functions in vegetative or minimally conscious patients. This approach
could eventually help determine the neurological outcome and make individual
blueprints of the preserved brain activities in severely brain injured patients.

PMID: 17992080 [PubMed – in process]

4: Curr Opin Neurol. 2007 Dec;20(6):620-6.

Pain assessment and management in disorders of consciousness.

Schnakers C, Zasler ND.

Coma Science Group, University of Liege, Liege, Belgium.
c.schnakers@student.ulg.ac.be

PURPOSE OF REVIEW: Pain and suffering controversies in persons with disorders of
consciousness continue to be debated by the scientific, legal and medical ethics
communities. This review examines the current knowledge base for guiding
decisions regarding assessment and management of pain in persons with disorders
of consciousness. RECENT FINDINGS: Studies have shown that brain processing
linked to pain in persons in a vegetative state is incomplete and is processed
only at a primary and not higher secondary level. Therefore, such painful stimuli
would not reach the threshold for conscious experience. In contrast, persons in a
minimally conscious state have been shown to have brain activation patterns to
pain similar to controls. Therefore, these patients may have sufficient cortical
integration and access to afferent information to allow for nociceptive stimuli
to be consciously processed. Data to date do not allow for differentiation of the
degree of any conscious pain experience or determination of whether individuals
with disorders of consciousness are able to suffer. SUMMARY: Pain and suffering
should be considered in all persons with disorders of consciousness and
adequately treated. Behavioural assessment scales developed for patients unable
to speak could be used to assess pain. Future studies should focus on
methodologies for specific pain measures relevant to this unique and challenging
patient population.

Publication Types: Research Support, Non-U.S. Gov’t

PMID: 17992079 [PubMed – in process]

5: Curr Opin Neurol. 2007 Dec;20(6):614-9.

Recent advances in behavioral assessment of individuals with disorders of
consciousness.

Giacino JT, Smart CM.

JFK Johnson Rehabilitation Institute, Edison, New Jersey, USA.
jgiacino@solarishs.org

PURPOSE OF REVIEW: The burden of proof for establishing diagnosis and prognosis
in patients with disorders of consciousness lies with behavioral assessment
methods. The current review discusses recent advances in understanding the
strengths and weaknesses of this methodology. RECENT FINDINGS: Behavioral
assessment methods remain the ‘gold standard’ for establishing diagnosis and
prognosis in patients with disorders of consciousness, although their
psychometric integrity and clinical utility remain largely unproven. While the
Glasgow Coma Scale maintains its standing in the trauma setting, there are
ongoing concerns regarding testing confounds and interrater reliability. The Full
Outline of UnResponsiveness, an emerging alternative, is more sensitive to
detection of locked-in syndrome but may fail to identify patients in the
minimally conscious state. Recent studies investigating the relationship between
behavioral and neurophysiologic measures of conscious awareness have revealed
important dissociations between behavioral response profiles and corresponding
neural activity. SUMMARY: Further research is needed on the psychometric
properties of existing behavioral assessment methods for disorders of
consciousness. Although dissociations between behavioral and neurophysiologic
findings caution against overreliance on behavioral metrics for detection of
conscious awareness, we expect there will be increased effort toward combining
these methodologies to increase diagnostic accuracy and prognostic specificity in
patients with disorders of consciousness.

Publication Types: Research Support, U.S. Gov’t, Non-P.H.S.

PMID: 17992078 [PubMed – in process]

6: Curr Opin Neurol. 2007 Dec;20(6):609-13.

What is it like to be vegetative or minimally conscious?

Laureys S, Boly M.

Coma Science Group, Cyclotron Research Centre and Neurology Department,
University of Liège, Liège, Belgium. steven.laureys@ulg.ac.be

PURPOSE OF REVIEW: Patients in a vegetative or minimally conscious state continue
to pose problems in terms of diagnosis, prognosis and treatment. Despite recent
waves of international media attention following Terri Schiavo’s death and the
‘miracle recovery’ of Terry Wallis, research efforts aimed at increasing our
knowledge about brain function in these conditions remain scarce and must address
a series of difficulties, including financial and ethical barriers. Here we
review current possibilities and limitations of clinical and para-clinical
assessment of chronic disorders of consciousness. RECENT FINDINGS: During the
past year the field has witnessed publication of significant, yet isolated, case
reports in top-ranking journals, including Science and Nature. Such milestone
reports and other impressive recent technological advances in the study of
vegetative and minimally conscious patients reveal enthralling areas of science
that must find their way to clinical medical reality. SUMMARY: Consciousness is a
subjective experience whose study has remained within the purview of philosophy
for millennia. That has finally changed, and empirical evidence from functional
neuroimaging offers a genuine glimpse at a solution to the infamous mind-body
conundrum. New technological and scientific advances offer the neurological
community unique ways to improve our understanding and management of vegetative
and minimally conscious patients.

Publication Types: Research Support, Non-U.S. Gov’t

Here (below) is the summary of the rules for participating and posting in Nature Network. My thanks to Corie Lok and the NN team for this information.

Best

Alfredo

Community guidelines

To ensure that everyone has an enjoyable time on Nature Network, we ask you to please follow a few basic ground rules.
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For those who are interested in the relation of quantum theory, biology and cognition, here are some sites:

a) Quantumbionet This site and the journal Quantum Biosystems are accepting new corraborators/submissions (please check the letter below);
b) Stuart Hameroff’s Quantum Consciousness
c) The journal Neuroquantology
d) Brazilian electronic journal ‘Informação e Cognição’, where I organized a number on Quantum Cognition.

Best Regards,

Alfredo

FORWARDED LETTER:

Dear QBN member

I am launching the international campaign “revitalizing the Quantumbionet”

During the first year of life the Quantumbionet has growing in interests and new outstanding members joint the network.

Our activities are still low but with the cooperation of everybody some new interesting things will be done.

You can rivitalize the network simply by inviting a new member you consider
of value for the quantumbionet

Another useful action should be a suggestion to improve the activities of
the QBN

The 2nd quantumbionet workshop will be organized this year

The Quantum Biosystems Journal should be revitalize either by submitting a
paper or a review

I hope to have a feedback from each of you

With best regards

Prof. Massimo Pregnolato

Source: World Science

Feb. 19, 2008
Courtesy University of Leicester
and World Science staff

In a study billed as an ex­plora­t­ion in­to the realm of “con­scious­ness,” re­search­ers claim to have found brain cells that be­come very busy only when some­thing is con­sciously no­ticed.

Try­ing to un­der­stand what cre­ates con­sciousness—the sense of be­ing alive and aware—is one of the all-time most ex­as­per­at­ing prob­lems in sci­ence. The key stum­bling block: even if one knew every brain mech­an­ism un­der­ly­ing con­scious­ness, there would still be no ap­par­ent way to see or meas­ure the ac­tu­al pro­duc­tion of con­sciou­sness.

For now, many re­search­ers fig­ure they may as well just do the best they can in un­rav­el­ing those phys­i­cal mech­an­isms. The new stu­dy, led by Qui­an Qui­roga of the Uni­ver­s­ity of Leices­ter, U.K., is among those de­signed to at­tack that ques­tion.

Vol­un­teers were shown pic­tures on a com­put­er screen very briefly­—for a time just at the edge of be­ing long enough to be no­tice­a­ble. The par­t­ici­pants were asked each time wheth­er they saw the pic­ture or not. Some­times the ex­act same vis­u­al in­put was no­tice­a­ble on one tri­al and not on an­oth­er, for the same per­son, Qui­an Qui­roga said.

The re­search­ers ex­am­ined what was hap­pen­ing in the brain dur­ing this. Cer­tain neu­rons, or brain cells, “re­sponded to the con­scious per­cep­tion in an ‘all-or-none’ way,” Qui­an Qui­roga said: they dra­mat­ic­ally changed their rate of fir­ing sig­nals, only when pic­tures were rec­og­nized. These neu­rons were in the me­di­al tem­po­ral lobe, a re­gion deep in­side the brain of­ten as­so­ci­at­ed with mem­o­ry.

For ex­am­ple, in one pa­tient, a neu­ron in the hip­pocam­pus—a struc­ture al­so in that area—“fired very strongly to a pic­ture of the pa­tient’s broth­er when rec­og­nized and re­mained com­pletely si­lent when it was not,” Qui­an Qui­roga said. “An­other neu­ron be­haved in the same man­ner with pic­tures of the World Trade Cen­tre.” The vol­un­teers were pa­tients who had to un­dergo ep­i­lep­sy sur­gery.

“Based on the fir­ing of these neu­rons it was pos­si­ble to pre­dict far above chance wheth­er a pic­ture was rec­og­nized or not,” Quian Quiroga said. Al­so, “a pic­ture flashed very briefly gen­er­at­ed nearly the same re­spon­se—if rec­og­nized—as when shown for much long­er per­i­ods of time.”

The find­ings are to ap­pear this week in the early on­line edi­tion of the re­search jour­nal Pro­ceed­ings of the Na­tio­n­al Aca­de­my of Sci­en­ces.

Po­ten­tial ap­plica­t­ions of the work in­clude the de­vel­op­ment of “neu­ral pros­thet­ic” de­vices to be used by par­a­lysed pa­tients or am­putees, Quian Qui­roga said. A spi­nal in­ju­ry pa­tient, such as the late Chris­to­pher Reeve, can think about reach­ing a cup of tea, but the mus­cles don’t get the or­der. Neu­ral pros­the­ses are de­signed to read these com­mands di­rectly from the brain and trans­mit them to bi­on­ic de­vices such as a robotic arm.

The find­ings, Quian Qui­roga said, could al­so have im­plica­t­ions treat­ment of pa­tients with patholo­gies of the hip­po­cam­pal forma­t­ion, such as ep­i­lep­sy, Alzheimer’s dis­ease and schiz­o­phre­nia.

Cerebral Cortex, Vol. 11, No. 10, 954-965, October 2001
© 2001 Oxford University Press

New Evidence for Distinct Right and Left Brain Systems for Deductive
versus Probabilistic Reasoning
Lawrence M. Parsons and Daniel Osherson1
University of Texas Health Science Center at San Antonio, San Antonio,
TX and
1 Rice University, Houston, TX, USA

Lawrence M. Parsons, Director, Cognitive Neuroscience Program,
Division of Behavioral and Cognitive Sciences, Directorate for Social,
Behavioral, and Economic Sciences, National Science Foundation, 4201
Wilson Boulevard, Arlington, VA 22230, USA.

Deductive and probabilistic reasoning are central to cognition but the
functional neuroanatomy underlying them is poorly understood. The
present study contrasted these two kinds of reasoning via positron
emission tomography. Relying on changes in instruction and
psychological `set’, deductive versus probabilistic reasoning was
induced using identical stimuli. The stimuli were arguments in
propositional calculus not readily solved via mental diagrams.
Probabilistic reasoning activated mostly left brain areas whereas
deductive activated mostly right. Deduction activated areas near right
brain homologues of left language areas in middle temporal lobe,
inferior frontal cortex and basal ganglia, as well as right amygdala,
but not spatial–visual areas. Right hemisphere activations in the
deduction task cannot be explained by spill-over from overtaxed, left
language areas. Probabilistic reasoning was mostly associated with
left hemispheric areas in inferior frontal, posterior cingulate,
parahippocampal, medial temporal, and superior and medial prefrontal
cortices. The foregoing regions are implicated in recalling and
evaluating a range of world knowledge, operations required during
probabilistic thought. The findings confirm that deduction and
induction are distinct processes, consistent with psychological
theories enforcing their partial separation. The results also suggest
that, except for statement decoding, deduction is largely independent
of language, and that some forms of logical thinking are non-diagrammatic.

ALSO SEE:

Oaksford, M., and Chater, N., (2001) “The probabilistic approach to
human reasoning” IN Trends in Cognitive Sciences Vol 5. No8 August
2001: 349-357

(published PRIOR to the above) From the intro:

“In a standard reasoning task, performance is compared with the
inferences people should make according to logic, so a judgement can
be made on the rationality of people’s reasoning. It has been found
that people make large and systematic (i.e. non-random) errors, which
suggests that humans might be irrational. However, the probabilistic
approach argues against this interpretation” (p349)

The 12th Annual Meeting of the Association for the Scientific Study of Consciousness

Location: Gis Convention Center, National Taiwan University, Taipei, Taiwan
Date: June 19-22, 2008
Contact: assc12@ym.edu.tw

We are glad to announce that the 12th annual meeting of Association for Scientific Study of Consciousness will be held for the first time in Asia during 19-22 June, 2008, in Taipei, Taiwan.
The conference will take place at the heart of Taipei city, National Taiwan University.

Taipei is the home of Taipei 101, currently the tallest building in the world, and the National Palace Museum, with the world’s most sophisticated collection of Chinese art/antiques.
Within a short drive, the famous marble Taroko Gorge, sub-tropical forests covering towering mountains, and rising cliffs overlooking the Pacific Ocean are all within your reach.

Please join us in a meeting that will both stimulate your mind and senses at ASSC 12, Taipei.
To enquire about the meeting, please mail to assc12@ym.edu.tw

Presidential Address:
David Rosenthal, City University of New York, USA

Confirmed Keynote Speakers:
Thomas Metzinger, The Johannes Gutenberg-Universitat Mainz, Germany, topic: The Self
Mitsuo Kawato, Advanced Telecommunications Research Institute International, Japan, topic: Engineering Consciousness
Tetsuro Matsuzawa, Kyoto University, Japan, topic: The Mind of the Chimpanzees
Susana Martinez-Conde, Barrow Neurological Institute,USA, topic: Microsaccades: Windows on the Mind

Confirmed Symposium Speakers:
Ned Block, New York University, USA
Victor Lamme, University of Amsterdam, the Netherlands
Sid Kouider, Ecole Normale Superieure, France
Barbara Jones, McGill University, Canada
Donald Pfaff, Rockefeller University, USA
Steven Laureys, University of Liege, Belgium
Haibo Di, Zhejiang University, China
Charles Spence, University of Oxford, UK
Keiji Tanaka, RIKEN Brain Science Institute, Japan
Glyn Humphreys, University of Birmingham, UK
Shaul Hochstein, Life Sciences Institute and Neural Computation Center, Israel
Tim Bayne, University of Oxford, UK
Ryan McKay, Queen’s University Belfast, UK
Ian Gold, McGill University, Canada
Robyn Langdon, Macquarie University, Australia

Confirmed Tutorial Workshops:
Antoine Bechara, topic: Emotions, Feelings, and Decision-Making
Juliane Wilcke, topic: The Evolutionary Function of Consciousness
Jennifer Windt & Thomas Metzinger, topic: Neurophilosophical Approaches to the Dreaming Mind – a Contrastive Analysis of Dreaming and Wakefulness
Tim Bayne & Jakob Hohwy, topic: Creature Consciousness and State Consciousness: Explanatory Strategies in the Study of Consciousness
Andrew Brook, topic: Consciousness Terminology
Shigeru Kitazawa & Shin’ya Nishida, topic: Adaptive Anomalies in Conscious Time Perception

ASSC12 Poster Contest Winner:
Juliane Wilcke, University of Canterbury, New Zealand

News Coverage of ASSC11:
Nature New York Times

Sponsors: National Science Council Ministry of Education National Yang Ming University National Taiwan University China Medical University Mind Science Foundation

The eighth biennial Tucson conference continues an interdisciplinary tradition of intense, far-ranging and rigorous discussions on all approaches to the fundamental issue of how the brain produces conscious experience
Overview
The program is set for the biennial Tucson conference ‘Toward a Science of Consciousness’, April 8-12, 2008. Held in even-numbered years since 1994, the Tucson conferences are the pre-eminent world gatherings on all approaches to the profound and fundamental question of how the brain produces conscious experience, a question which addresses who we are, the nature of reality and our place in the universe.
An estimated 600 attendees from 6 continents will participate in 400 presentations included in 21 Pre-Conference Workshops, 12 Plenary sessions, 21 Concurrent Talk sessions, 2 Poster Sessions and, for the first time, an interactive Art and Technology of Consciousness Exhibit.

Plenary Session Overview:

Is Attention Necessary for Consciousness?

Can we be conscious of objects to which we are not paying attention? Neuroscientists Stanislas Dehaene and Christof Koch and philosopher Michael Tye discuss ‘top-down’ (frontal to posterior cortex) brain attentional mechanisms and their relation to consciousness. If attention doesn’t cause consciousness, what does?

Libet, Intentionality and the Timing of Conscious Experience

Does consciousness play a role in action, or does it just tag along for the ride? A panel of experts discuss recent evidence pertaining to Benjamin Libet’s pioneering work on the backward time referral of conscious experience, intention and free will.

Keynote: Consciousness and the Three Bears

What would a proper theory of consciousness look like? Philosopher Andy Clark suggests that qualitative perceptual experience (consciousness) occurs within the brain in a zombie-free zone of just the right amount of access to internal information processing.

Sex and Consciousness

How can we understand the special sort of consciousness present during sexual experience and orgasm? Neuroscientist Barry Komisaruk discusses functional brain imaging during female orgasm, and author Jennifer Wade describes transcendental sexual mental states. A panel surveys sexual experience, Tantric sex and altered sexual states.

Is Consciousness Local or Global?

Cognitive neuroscientists Bernard Baars, Rafael Malach and Naotsugu Tsuchiya debate whether consciousness requires global, distributed brain activity, or can occur locally, restricted to more specific brain regions. What specific type of neuronal activity corresponds with consciousness?

Keynote: Consciousness and Gamma Synchrony EEG

Pioneer neuroscientist Wolf Singer describes how synchronized electrical activity in the beta and gamma EEG ranges are distributed throughout wide regions of brain, and represent the best measurable correlate of consciousness. How is synchrony mediated globally? How does it relate to consciousness?

Introspection and the Richness of Consciousness

Is conscious experience rich in detail and meaning, or sketchy and minimalist? Can we answer this question from the inside? Philosopher Eric Schwitzgebel asks whether there is consciousness outside attention, philosopher Susanna Siegel discusses whether perceptual consciousnesss includes high-level meaning, and psychologist Chris Heavey CH addresses whether we have unsymbolized conscious thought.

Sub-Neural and Quantum Approaches to Consciousness

Is quantum coherence necessary for consciousness? Is it feasible in the warm brain? Biophysicist Gustav Bernroider and physician Stuart Hameroff discuss neuronal brain behaviors which seem to demand quantum coherence, the question of decoherence at brain temperature, and the neuronal functional organization required for consciousness.

Brain Imaging as Mind Reading Technology

Neuroscientists Frank Tong, Adrian Owen and Daniel Langleben discuss use of functional brain imaging to determine specific content of conscious perceptions, presence of consciousness in comatose patients, and whether or not a subject is lying or telling the truth. Can technological mind-reading be reliable? What are the ethical considerations?

Anomalies of Consciousness

Does extra-sensory perception actually occur? Rupert Sheldrake will present his controversial evidence for non-local perceptions (e.g. ‘the sense of being stared at’) as a product of evolution. A panel of critical discussants will evaluate his claims.

Consciousness and Psychedelic Drugs

What can we learn about consciousness from altered states? Biologist Tom Ray discusses discusses the chemical basis of the entire space of altered states. Anthropologist Frank Echenhofer reports on experiences with the shamanic psychedelic brew ayahuasca in the Amazon, including artistic accounts of mental imagery and measurements of gamma synchrony EEG.

Development of Consciousness

Are babies more conscious than adults? Psychologist Alison Gopnik suggests babies are more conscious, but less focused, than adults. Do babies lack ‘top-down’ attentional mechanisms? Psychologist Phil Zelazo discusses how consciousness correlates with embryonic, childhood and adolescent development. Sarah Akhter will present beeper studies of the first-person perspective on development of consciousness during adolescence.

Pre-Conference Workshops

Globalist theories (Baars), Mathematical physics (Freeman etc), Social brain (Craik, Whitehead), East/West consciousness (Droege, Maitra), Quantum mechanisms (Bernroider, Sheehan, Hameroff), Philosophical theories (Kriegel), Vision (Martinez-Conde, Macknik), Libet, time and action (Sinnott-Armstrong, Nadel etc.), Lucid dreaming (LaBerge), Neurological disturbances (Feinberg), Julian Jaynes (McVeigh, Kuijsten), Panpsychism (Skrbina, Deiss), Ayahuasca (Echenhofer), Transformations (Schlitz, Vieten), Inner experience (Hurlburt, Schwitzgebel), Higher states and orgasm (Ormos), Attention and consciousness (Koch, Tsuchiya), How do you feel? (Craig), Unity of consciousness (Bayne)

Concurrent Sessions (5 speakers per session)

Materialism/Dualism, Phenomenology of Thought, Emotion/Theory of Mind, Vision, Psychopathology and Therapy, Time, Social Approaches, Panpsychism, Contents of Consciousness, CNCC, Neurobiological Models, Altered States, Consciousness and Julian Jaynes, Art and Literature, Theories of Consciousness, Concepts of Consciousness, Action/Embodiment,Unconscious States, Physics, Evolution of Consciousness, Technology

Poster Sessions

Approximately 300 posters will be presented Wednesday and Friday evenings

Art and Technology Exhibit (Tuesday, Wednesday, Friday evenings, curated by Rene Stettler)

NeuroFloat

Meehae Song & Steven Barnes

Interactive EEG navigates user through real-time 3-D visualization of the human brain.

Optimal Experience

TingTing Chen

Technology of attention and ordering of consciousness

Hello World

Margaret Dolinsky

Iluminated script collage of phenomenal experience

BrainPaint

Deborah DuSold, William Scott

EEG biofeedback user generates dynamic abstract art

Psychosomatic Art

Ana E. Iribas-Rudin

Bodily changes from unconscious motivations

Lucid 2.0

Gino Yu

A virtual reality platform designed for interactive first person experience

Social Events

Tuesday evening Welcome Reception, Tucson Convention Center (TCC)

Attendees meet and mingle with food and drinks indoors (amidst book and art/technology exhibits) and outdoors under mesquite trees on TCC veranda

Thursday evening conference dinner, Arizona-Sonora Desert Museum

Free afternoon allows visits to world-famous Desert Museum followed by dinner and drinks in spectacular Baldwin room with panoramic vista

Friday night Poetry Slam/Zombie Blues Talent Show, Tucson Convention Center

Participants recite poems about consciousness, and sing verses of ‘The Zombie Blues’ to a late-night cheering and jeering audience.

Saturday night ‘End-of-Consciousness’ Party, Cushing Street Bar and Grill

The talent show and End-of-Consciousness Party will feature ‘The Brains’, a new band (alter ego of ‘The Theory’) performing three new songs ‘I’m your brain’, ‘You think therefore you are’ and ‘Soul Organ’.

Side Trips

Kitt Peak Observatory, Mars Mission Center, Sabino Canyon and DeGrazia Gallery, San Xavier Mission, Colossal Cave

Book/Commercial Exhibits

Oxford University Press

MIT Press

Journal of Consciousness Studies

Conference Recording Services
Applied fMRI San Diego
Center for Consciousness Studies

TUCSON 2008 PROGRAM COMMITTEE
Bernard Baars, Neurosciences Institute, San Diego
David Chalmers, Australian National University
Anthony Freeman, Journal of Consciousness Studies
Stuart Hameroff, University of Arizona
Valerie Gray-Hardcastle, Virginia Tech University
Terry Horgan, University of Arizona
Al Kaszniak, University of Arizona
Christof Koch, California Institute of Technology
Uriah Kriegel, University of Sydney
Hakwan Lau, Columbia University
Marilyn Schlitz, Institute of Noetic Sciences

Conference/Center Manager

Arlene ‘Abi’ Montefiore

June 24-27, 2008 • São Luís, Brazil

http://www.ufma.br/bics2008

General Chair: Allan Kardec Barros
Depto. Eng. Eletrica,
Universidade Federal do Maranhao, Brazil.

to be held at: Pestana São Luís, São Luís do Maranhão Brasil Hotels
http://www.pestana.com/hotels/en/hotels/southamerica/SaoLuisMaranhao/SaoLuis/Home/PestanaSaoLuis.htm

PAPER SUBMISSION DEADLINE EXTENDED: 15 February 2008

Confirmed speakers:

Shun-ichi Amari (Brain Science Institute, RIKEN, Japan)

José Carlos Príncipe (University of Florida Gainsville, USA)

Second International ICSC Symposium on Models of Consciousness (MoC
2008) From foundations to implementations
Chair: Ron Chrisley , University of Sussex, U.K.

Fourth International ICSC Symposium on Biologically Inspired Systems
(BIS 2008) Design and implementation of biologically inspired and neuromorphic
systems
Chair: Leslie Smith, University of Stirling, U.K.

Third International ICSC Symposium on Cognitive Neuro Science (CNS
2008) Models of cognitive systems;
Chair: Igor Aleksander, Imperial College London, U.K

Fifth International ICSC Symposium on Neural Computation (NC 2008) Progress in neural systems
Chair: Amir Hussain, University of Stirling, U.K.

Why this conference, and who should attend:

The biennial Brain Inspired Cognitive Systems 2008 aims to bring
together
leading scientists and engineers who use analytic, formal or
computational
methods both to understand the prodigious processing properties of
biological
systems, particularly the brain, and to exploit such knowledge to
advance
technology towards ever higher levels of cognitive competence. The
four major
symposia are organized in patterns that encourage
cross-fertilization across the symposia topics. This emphasizes
that, following
the success of BICS 2004 (Stirling, Scotland) and BICS 2006
(Greece), BICS 2008
will continue be a major point of contact for
researchers and practitioners who can benefit from not only the
major advances
in their specialist fields but also from the diversity of each
other’s views.
Each of the four mornings is devoted to papers that will be selected
for their
clear novelty and proven scientific impact, while the afternoons
will provide
scope for researchers to present their current work and discuss
their aims and
ambitions. Debates across disciplines will unite researchers with
differing
perspectives.

You may submit your abstract here

SUB-THEMES (including, but not limited to):

Models of consciousness: (MoC)
Global Workspace Theory
Imagination/synthetic phenomenology
Virtual Machine Approaches
Axiomatic Models
Control Theory/Methodology
Developmental/Infant Models
Will/volition/emotion/affect
Philosophical implications
Grounding in neurophysiology
Enactive approaches
Heterophenomenology

Cognitive Neuroscience (CNS)
Attentional Mechanisms
Cognitive Neuroscience of Sensory Modalities
CN of volition Affective
Systems Language Cortical Models
Sub-Cortical Models
Cerebellar Models
Eventlocation in the brain
Others

Biologically Inspired Systems (BIS)
Brain Inspired (BI) Vision
BI Audition and sound processing
BI Other sensory modalities
BI Motion processing
BI Robotics
BI Evolutionary systems
BI Oscillatory systems
BI Signal processing
BI Learning
Neuromorphic systems
Others

Neural Computation (NC)
Hybrid Systems
NC Learning
NC Control Systems
NC Signal Processing
Architectures
Devices
Pattern Classifiers
Support Vector Machines
Fuzzy or Neuro-Fuzzy Systems
Evolutionary Neural Networks
Biological Neural Network Models
Applications
Others

Important Dates:
July 2008
Acceptance – March/April/2008

Publications:
selected, expanded and revised BICS2008 papers will be published in
follow-on
special issues of international journals

ORGANIZED BY:

Planning Division
ICSC Interdisciplinary Research
NAISO Natural and Artificial Intelligence Systems Organization Canada

What Are We Thinking When We (Try to) Solve Problems?
New research indicates what happens in the brain when we’re faced with a dilemma
By Nikhil Swaminathan

Aha! Eureka! Bingo! “By George, I think she’s got it!” Everyone knows what it’s like to finally figure out a seemingly impossible problem. But what on Earth is happening in the brain while we’re driving toward mental pay dirt? Researchers eager to find out have long been on the hunt, knowing that such information could one day provide priceless clues in uncovering and fixing faulty neural systems believed to be behind some mental illnesses and learning disabilities.

Researchers at Goldsmiths, University of London report in the journal PLoS ONE that they monitored action in the brains of 21 volunteers with electroencephalography (EEG) as they tackled verbal problems in an attempt to uncover what goes through the mind—literally—in order to observe what happens in the brain during an “aha!” moment of problem solving.

“This insight is at the core of human intelligence … this is a key cognitive function that the human can boast to have,” says Joydeep Bhattacharya, an assistant professor in Goldsmiths’s psychology department. “We’re interested [in finding out] whether—there is a sudden change that takes place or something that changes gradually [that] we’re not consciously aware of,” he says. The researchers believed they could pin down brain signals that would enable them to predict whether a person could solve a particular problem or not.

In many cases, the subjects hit a wall, or what researchers refer to as a “mental impasse.” If the participants arrived at this point, they could press a button for a clue to help them untangle a problem. Bhattacharya says blocks correlated with strong gamma rhythms (a pattern of brain wave activity associated with selective attention) in the parietal cortex, a region in the upper rear of the brain that has been implicated in integrating information coming from the senses. The research team noticed an interesting phenomenon taking place in the brains of participants given hints: The clues were less likely to help if subjects had an especially high gamma rhythm pattern. The reason, Bhattacharya speculates, is that these participants were, in essence, locked into an inflexible way of thinking and less able to free their minds, and thereby restructure the problem before them.

“If there’s excessive attention, it somehow creates mental fixation,” he notes. “Your brain is not in a receptive condition.”

At the end of each trial, subjects reported whether or not they had a strong “Aha!” moment. Interestingly, researchers found that subjects who were aware that they had found a new way to tackle the problem (and so, had consciously restructured their thinking) were less likely to feel as if they’d had eureka moment compared to more clueless candidates.

“People experience the “Aha!” feeling when they are not consciously monitoring what they are thinking,” Bhattacharya says, adding that the sentiment is more of an emotional experience he likens to relief. “If you’re applying your conscious brain information processing ability, then you’re alpha.” (Alpha brain rhythms are associated with a relaxed and open mind; volunteers who unwittingly solved problems showed more robust alpha rhythms than those who knowingly adjusted their thinking to come up with the answer.)

He says the findings indicate that it’s better to tackle problems with an open mind than by concentrating too hard on them. In the future, Bhattacharya says, his team will attempt to predict in real-time whether a stumped subject will be able to solve a vexing problem and, also, whether they can manipulate brain rhythms to aid in finding a solution.

The second probe into problem-solving focused on the anterior cingulate cortex (ACC), a region in the front of the brain tied to functions such as decision making, conflict monitoring and reward feedback. A team at the University of Lyon’s Stem Cell and Brain Research Institute in Bron, France reports in Neuron that it verified that the ACC helps detect errors during problem solving (as previously discovered), but also that it does so by acting more as a general guide, monitoring and scoring the steps involved in problem solving, pointing out miscalculations as well as success.

The team discovered this by recording electrical activity in the brains of two male rhesus monkeys as they tried to determine which targets on a screen would result in a tasty drink of juice. “When you’re trying to solve a problem, you need to search; when you discover the solution, you need to stop searching,” says study co-author Emmanuel Procyk, coordinator of the Institute’s Department of Integrative Neurobiology. “We need brain areas to do that.”

He says that researchers observed increased neuronal activity in the animals’ ACCs when they began searching. When the monkeys hit the jackpot, there was still heightened activity in the ACC (though only a selective population of nerve cells remained hopped up), indicating that the region is responsible for more than simply alerting the rest of the brain when errors are made. Once the monkeys got the hang of it—and routinely pressed the correct target—ACC activity slowed.

“What we think based on this experiment and other experiments,” Procyk says, “is that this structure is very important in valuing things.” It essentially scores each of the monkey’s behaviors as successful or not successful. “It is an area,” he adds, “that will help to decide when to shift from the functioning that goes on when [the brain is] learning to when the learning [is] done.”

Procyk says that if this system is compromised, it could have implications for issues such as drug dependency. If the ACC is functioning abnormally, he says, it could overvalue drugs, leading to addiction. (Other studies have shown that an impaired cingulate cortex can result in maladaptive social behavior and disrupted cognitive abilities.)

Alas, the ultimate “Aha!” moment for researchers probing problem solving is likely is far off, but at least the latest research may help them avoid an impasse.

Exciting new methods are poised to start revealing how circuits of neurons process information and mediate behavior. Recently, neuroscientists mapped neural connections in mice by genetically tagging neurons with nearly 100 fluorescent hues. Others have been using lasers to control the electrical activity of individual neurons in the brains of rodents, thanks to light-sensitive ion channels introduced by genetic engineering. Meanwhile, a magnetic resonance method called diffusion tensor imaging is providing new detail about connections between regions of the human brain. These techniques should yield important insights into how neural circuits work—and how they break down in brain disorders.”

Source: Science

Several links to the original papers are displayed in the page.

1: Psychol Neuropsychiatr Vieil. 2007 Dec;5(4):249-60.

[Consciousness and emotion.]

[Article in French]

Carton S.

Université Montpellier III Paul-Valéry, Département de psychologie, Section de
psychologie clinique, Montpellier.

This article focuses on the processes that lead to awareness of our own emotions,
which deserve particular attention in contemporary models of emotional
consciousness. The subjective component of emotion, or emotional experience, was
for a long time the most neglected aspect in the study of emotions although it
already constituted the initial point of discussion in the famous William James
still asked question : What is an emotion? More than a century later,
contemporary theories debate about this heritage. We examine the successive
historic contributions to the question of the determinants of our own emotional
experience: from James-Lange bodily changes to cognitive appraisal theories, also
relating the major role that the fundamental emotions theory attributed to facial
expressions. Twenty years after the debate about primacy of cognition or emotion,
both physiological-somatic and cognitive components are integrated in
contemporary approaches to emotions. However, their respective degree of
implication varies according to the different levels of emotional consciousness
which are modelized. It is on the last level that present models focuse, level
that leads to consciousness of our emotional experience, benefiting from the
contributions of cognitive neurosciences. Models differ according to the role
devoted to neuronal substrates in determining emotional experience, but they
converge on the specification of a last level of consciousness, which is the only
one that allows the subject to be conscious of emotion as it is experienced
(feeling) and that what he is experiencing is an emotion. Then, different models
of emotional consciousness account for different varieties of emotion experience
and also for various cases of << unconscious >> emotions, that is occurrence of
emotion with a lack of awareness.

Publication Types: English Abstract

PMID: 18048103 [PubMed – in process]

2: Psychol Neuropsychiatr Vieil. 2007 Nov 30;5(4):261-267.

[A scientific model of consciousness: implications for neuropsychiatic diseases.]

[Article in French]

Gaillard R, Del Cul A.

Unité Inserm 566, Neuro imagerie cognitive, Centre neurospin CEA/SAC/DSV/DRM,
Gif-sur-Yvette.

Consciousness is an essential property of human cognition. According to the <<
Global neuronal workspace >> hypothesis designed by Dehaene et al., consciousness
results from amplification and synchronisation of distant processors.
Frontoparietal loops play a crucial role in this large scale synchronisation. At
any given time, many modular cerebral networks are active in parallel and process
information unconsciously. An information becomes conscious, however, if the
neural population that represents it is mobilized by top-down attentional
amplification into a brain-scale state of coherent activity. This long-distance
connectivity makes the information available to a variety of processes including
perceptual categorization, long-term memorization, evaluation, and intentional
action. Behavioral as well as neuroimaging studies using masked subliminal
perception support this theoretical view. Among neuropsychiatric disorders, many
neuroscientific studies have been devoted to schizophrenia. Some of them conclude
on a global brain dysconnectivity rather than on specific and localised
perturbations. Hence conscious integration may be the core deficit in cognitive
disabilities observed in schizophrenia. As shown in recent results, threshold for
access to consciousness in schizophrenic patients compared with controls is
elevated whereas unconscious processes, such as the ones involved in subliminal
priming remain effective. We conclude on the potential use of the “global
neuronal workspace” model in other neuropsychiatric diseases such as Alzheimer’s
disease or multiple sclerosis.

PMID: 18048104 [PubMed – as supplied by publisher]

Sensors and synchronicity

Ruth Heildelbeger

Synaptic communication is triggered by action potentials, but
neurons also
talk to each other in between action potentials. Specific
intracellular-calcium sensors regulate these conversations… In the
presynaptic neuron, voltage-gated calcium channels are activated in
response
to an action potential, allowing the entry of extracellular calcium.
This
triggers the fusion of neurotransmitter-laden synaptic vesicles with
the
plasma membrane and the release of neurotransmitter molecules. Released
molecules bind to receptors on the postsynaptic neuron, initiating a
postsynaptic response. The close proximity of release sites, calcium
channels and synaptic vesicles, and the use of a calcium sensor for
release
with five low-affinity calcium-binding sites, lead to the generation
of a
burst of neurotransmitter release synchronous with the
stimulus1.
But neurons also secrete neurotransmitter through another, much less
well-understood mechanism called asynchronous release. On page
676of
this issue, Sun et
al. shed
light on asynchronous release, showing that it is mediated by an
unidentified calcium sensor with unexpected properties (...)

Nature 450, 676-682 (29 November 2007) | doi:10.1038/nature06308;

A dual-Ca2+-sensor model for neurotransmitter release in a central
synapse

Jianyuan Sun, Zhiping P.Pang, Dengkui Qin, Abigail T. Fahim, Roberto Adachi & Thomas C. Südhof
Abstract
Ca2+-triggered synchronous neurotransmitter release is well
described, but asynchronous release—in fact, its very
existence—remains
enigmatic. Here we report a quantitative description of asynchronous
neurotransmitter release in calyx-of-Held synapses. We show that
deletion of
synaptotagmin 2 (Syt2) in mice selectively abolishes synchronous
release,
allowing us to study pure asynchronous release in isolation (...)

[thanks to Malcolm Dean for calling my attention to this discovery – Alfredo]

All brain cells are the same, genetically speaking. Yet somehow they play vastly different roles, some directing movement, others participating in language or thought. Now, a study finds that a chemical known to turn genes on and off may be partially responsible for this division of labor. The results, researchers suggest, could help scientists better understand psychiatric and neurological diseases.
It takes more than genes to make people who they are. Identical twins, for example, can look and act differently even though they share the same DNA (ScienceNOW, 5 July 2005). Environmental factors likely contribute to this variation, but it also seems to depend on so-called epigenetic phenomena, activity that regulates genes without changing the DNA code (ScienceNOW, 12 April 2006). In the 1960s, researchers found that the addition of a molecule called a methyl group to cytosine, one of the four building blocks of DNA, could turn off genes. Since then, scientists have found that this process, called methylation, can also turn genes on and that it is linked to cancer (ScienceNOW, 31 January 2000) and short-term memory formation (ScienceNOW, 14 March).

Because no studies have surveyed methylation’s role in assigning marching orders to brain cells, geneticist Andrew Feinberg and psychiatric geneticist James Potash, both of Johns Hopkins University in Baltimore, Maryland, decided to investigate. Along with their colleagues, they compared possible methylation sites on 807 genes in 76 samples from human brains. Among the regions studied were the cerebellum, which controls movement, and the cerebral cortex, which controls language and memory. The team found that methylation patterns differed by brain region, indicating that epigenetics helps divide up the brain’s functions. These patterns proved more robust than differences in methylation linked to race, age, or sex, the team reports in the December issue of The American Journal of Human Genetics.

The study makes clear, Feinberg says, that “working on the brain without thinking about epigenetics is like working with a blindfold on.” By understanding normal methylation, he adds, researchers can begin to look at methylation gone wrong, possibly in autism, depression, bipolar disease, and schizophrenia.

Given that epigenetics has been shown to modify gene expression in other parts of the body, the brain results are not surprising, says psychiatrist Schahram Akbarian of the University of Massachusetts Medical School in Worcester. “One could say neuroscience is catching up with the rest of the field.”

ScienceNOW

Dale Antanitus is (or was) a pediatric physician in Harvard, who advanced some interesting hypotheses about the role of astrocytes.
These ideas are found in his site
One of them is that minor head trauma causes loss of consciousness by means of a perturbation of calcium waves in astrocytes:
“Equally mysterious are the mechanisms producing unconsciousness resulting from minor head trauma insufficient in force to cause any detectable injury. Mechanical perturbation has been shown to precipitate calcium waves in vitro. A blow to the head results in a mechanical compression wave traveling through the brain. This mechanical force could be sufficient to produce a pattern of widespread sequential calcium waves that reflect the shape and velocity of the mechanical compression wave. The astrocytic calcium waves so produced would be unrelated to, and for a while unresponsive to the influence of, normal sensory input. Meaningful interactions between astrocytes and synapses could be overwhelmed by the disruptively nonsensical mechanically induced calcium wave patterns. Despite the inability of the mechanical force to produce macro or microscopic injury, the brain—the person—would be “knocked out” or temporarily unconscious”

Below I link other papers about head concussion, and the proposed roles of astrocytes for memory and consciousness:
1) Giza CC, Hovda DA. The Neurometabolic Cascade of Concussion. J Athl Train. 2001 Sep;36(3):228-235. Freely available here
2) Caudle RM. Memory in astrocytes: a hypothesis.
Theor Biol Med Model. 2006 Jan 18;3:2. Freely available here
3) Robertson JM. The Astrocentric Hypothesis: proposed role of astrocytes in consciousness and
memory formation. J Physiol Paris. 2002 Apr-Jun;96(3-4):251-5. Non-free access here

Today this group completed 100 members from several countries and scientific areas.
Please reply to this message if you have suggestions for our activities.

Best Regards,

Alfredo

New life inside the depressed brain
Neuron growth may be key to mood disorder treatments, studies find
By Carey Goldberg, Globe Staff | November 19, 2007

Cut off from their usual social group, the three macaque monkeys fell into simian depression. They no longer took pleasure in anything. They lost status and did not seem to care.

Columbia University researchers gave three other exiled monkeys the antidepressant Prozac, and they showed no signs of depression. Later examination showed that in a key area deep in the monkeys’ brains – the seahorse-shaped hippocampus – myriad new cells had sprouted.

Then the scientists treated four more monkeys with X-ray radiation that blocked the hippocampus from making new cells. When those monkeys were sent into depressing exile, Prozac couldn’t help them. And their brains later showed no signs of new cells in the hippocampus.

That preliminary study, presented earlier this month at the annual Society for Neuroscience conference, adds the latest scientific backing to a hot theory of depression that has been gaining momentum – and drawing debate – for several years.

It goes like this: Depression, which affects at least 19 million Americans a year, can involve problems not only with chemical messengers such as serotonin, but with the very structure of the brain, with the neurons and their connections.

Research suggests that stress and depression can actually shrink parts of the brain and that anything that successfully lifts depression – be it exercise, drugs, or shock therapy – appears to involve a burst of new neurons in key areas.

The catchword for the hot theory is “neurogenesis” – meaning the creation of new neurons – and even enthusiasts hasten to caution that it is still only a theory. But it is compelling enough that some drug companies are already focusing on neurogenesis and various substances that boost it in hopes of generating better antidepressants.

The theory could explain, for example, why drugs like Prozac often take weeks to kick in, even though they change the brain’s chemistry within hours: It could take that long for the new neurons to develop. The theory also fits with findings that the longer a person has been depressed, the smaller their hippocampus. And with findings that depression can impair memory and learning, which depend in part on forming new neurons.

Depression and other mood disorders could actually act in the brain something like milder versions of neurodegenerative diseases – Alzheimer’s or Parkinson’s – with their atrophy and cell loss, said Dr. Ron Duman, a professor of psychiatry and pharmacology at Yale University. But with one key difference, he said: Neurodegenerative diseases are not normally reversible. Mood disorders usually are.

The theory “tends to tie in everything,” said Dr. Tarique Perera, the psychiatrist who presented the macaque study. “It’s the one theory that can encompass the neurotransmitters, the stress hormones, the structure problems and even certain behavioral aspects of depression.”

And recent research raises an exciting new possibility, he said: boosting neurogenesis may not only lift depression but actually prevent it.

The neurogenesis theory leans on surprising findings from the late 1990s: Contrary to longstanding dogma that adult brains are fully developed, scientists discovered that the human hippocampus, a center of learning and memory, continues to make new neurons throughout life.

Neurogenesis pioneer Dr. Fred Gage, of the Salk Institute, cautioned against oversimplifying the link with depression. At this point, it is not clear that the link between neurogenesis and depression is actually one of cause and effect.

Evidence from various avenues of research suggests that increasing neurogenesis helps alleviate depression, and reduced neurogenesis could exacerbate it, he said.

How could that be? How might the birth of new neurons affect mood?

That question tends to bring a lot of hand-waving from scientists, and possible answers remain sketchy. But the known link between neurogenesis and learning has led some to speculate that in a depressed state, a person becomes overfocused on the bad and unable to register the good, and in effect, that inability to shift gears is a failure to learn.

Researchers also note that though the hippocampus is seen as a hub of memory, it also appears to influence anxiety and has connections to centers of emotion in the deeper limbic brain, and could affect their activity.

Some people suffer from depression so intractable that no treatment works. According to the neurogenesis theory, part of the problem may be that because of chemical or structural alterations in their brains, they can no longer produce enough new neurons. But research has yet to address that possibility.

The neurogenesis theory also has troubling holes.

At this month’s giant Society for Neuroscience conference in San Diego, one challenge to the theory came from Shawn Kohler, a researcher at the University of Illinois at Urbana-Champaign.

In mice, it takes three or four weeks for new neurons to mature – about as long as it takes for people with depression to feel antidepressants kick in. Many researchers had assumed that the time scale must be the same in humans, but Kohler found that in monkeys, new neurons took a good 24 weeks to mature.

“We would only expect it to be longer in humans,” he said.

Some studies, like Perera’s, have shown that blocking neurogenesis also blocks the buoying action of antidepressants. “But other papers have come out recently showing that’s not always the case,” said Duman.

What is clear is that the evidence is very strong that increasing neurogenesis is at least a bellwether or a biomarker” that an antidepressant treatment is starting to work, he said.

It is also clear, researchers say, that new tools that may prove the neurogenesis theory true or false are quickly coming on line.

William Greenough, a prominent University of Illinois brain scientist is beginning to be able to label neurons in animals by when the cells were born, he said, and follow them through time.

And just this month, a team of researchers led by Grigori Enikolopov of Cold Spring Harbor Laboratory in New York announced that using technology related to MRI and a telltale marker for new cells, they had developed a noninvasive method to track neurogenesis in living humans. The first tool with such a capability, it could help researchers study brain cell changes in a variety of diseases from depression to cancer and stroke.

If such tools succeed, future psychiatrists may use signs of neurogenesis in their patients’ brains to tell quickly whether a treatment holds promise, instead of waiting weeks as they often must now.

“You could do this in the office to speed people’s antidepressant treatment,” said Dr. John Denninger, a Massachusetts General Hospital psychiatrist doing research related to neurogenesis. “You’d improve the odds that you’d actually give them something that would make them better.

Read the notice and comments at NatureNews

We are pleased to announce the launch of MindPapers, a new website
with a bibliography covering around 18000 published papers and online
papers in the philosophy of mind and the science of consciousness.
This site grew out of a combination of David Chalmers’ bibliography in
philosophy of mind and his page of online papers on consciousness, but
it is much larger and has many new capacities, programmed by David
Bourget. The site address is:

http://consc.net/mindpapers/

There is also a separate front end for “Online Papers on
Consciousness”. Where MindPapers now combines both offline published
papers and online papers from free and commercial sites, Online Papers
on Consciousness is devoted to free online papers (currently around
4700). It is based on the same database as MindPapers, but is
organized in a way to emphasize issues concerning consciousness and
cognitive science rather than the philosophy of mind. The address is

http://consc.net/online/

The MindPapers database contains 2773 papers on the philosophy of
consciousness (under 59 topics and subtopics) and 3917 papers on the
science of consciousness (under 71 topics and subtopics), as well as
thousands of papers on such related topics as perception,
intentionality, the philosophy of AI, and the philosophy of cognitive
science.

Capacities include (i) links and citation information throughout, (ii)
flexible navigation, display, and search options, (iii) the ability to
submit and edit entries, (iv) the capacity for automated off-campus
proxy access to commercial sites, and (v) a wealth of statistical
information.

We encourage everyone to try these sites to submit any relevant
material that we are missing (for a start, try searching on your own
name). There are tools on the site for submitting entries, as well as
for correcting entries and notifying us of any bugs and suggestions.

—David Chalmers and David Bourget chalmers@anu.edu.au; david.bourget@anu.edu.au Australian National University.

NEUROSCIENCE: Too Quick to Glimpse?

Katrina L. Kelner

An optical illusion can help define which parts of the brain are
responsible for human consciousness. People cannot consciously
perceive a
number flashed on a screen for 16 ms if it is quickly followed by
another
stimulus in the same area. As the time between the two stimuli
increases,
the first stimulus becomes visible; that is, it is accessible to the
person’s consciousness. Del Cul et al. recorded electrical brain
waves from people’s scalps as they were shown these stimuli and
reported to
the investigators whether they were visible or invisible. One brain
wave in
particular, P3, occurring 270 to 400 ms after the beginning of the
trial,
correlated with conscious perception of the stimulus. This wave
seems to
arise from sudden simultaneous activity in several parts of the brain,
specifically the frontal, parietal, and temporal cortices of both
hemispheres. These data are inconsistent with several proposed
correlates
of consciousness, including the rapid induced activity in the visual
areas
of the brain and the later more distributed, but still local, neural
reverberations. Rather, they suggest that conscious perception is
associated with a sudden global reverberation of neural activity,
about 300
ms after the stimulus, encompassing several cortical areas
bilaterally.

PLoS Biol. 5, 10.1371/journal.pbio.0050260 (2007).

Blood may help us think

MIT scientists propose that blood may help us think, in addition to its well-known role as the conveyor of fuel and oxygen to brain cells.

“We hypothesize that blood actively modulates how neurons process information,” explains Christopher Moore, a principal investigator in the McGovern Institute for Brain Research at MIT, in an invited review in the Journal of Neurophysiology. “Many lines of evidence suggest that blood does something more interesting than just delivering supplies. If it does modulate how neurons relay signals, that changes how we think the brain works.”

According to Moore’s Hemo-Neural Hypothesis, blood is not just a physiological support system but actually helps control brain activity. Specifically, localized changes in blood flow affect the activity of nearby neurons, changing how they transmit signals to each other and hence regulating information flow throughout the brain. Ongoing studies in Moore’s laboratory support this view, showing that blood flow does modulate individual neurons.

Moore’s theory has implications for understanding brain diseases such as Alzheimer’s, schizophrenia, multiple sclerosis and epilepsy. “Many neurological and psychiatric diseases have associated changes in the vasculature,” says Moore, who is also an assistant professor in MIT’s Department of Brain and Cognitive Sciences.

“Most people assume the symptoms of these diseases are a secondary consequence of damage to the neurons. But we propose that they may also be a causative factor in the disease process, and that insight suggests entirely new treatments.” For example, in epilepsy people often have abnormal blood vessels in the brain region where the seizures occur, and the hypothesis suggests this abnormal flow may induce epileptic onset. If so, drugs that affect blood flow may provide an alternative to current therapies.

The hypothesis also has important implications for functional magnetic resonance imaging, or fMRI, a widely used brain scanning method that indicates local changes in blood flow. “Scientists looking at fMRI currently regard blood flow and volume changes as a secondary process that only provides read-out of neural activity,” explains Rosa Cao, a graduate student in Moore’s lab and co-author of the paper. “If blood flow shapes neural activity and behavior, then fMRI is actually imaging a key contributor to information processing.”

Again, studies in Moore’s lab support this interpretation. For example, his fMRI studies of the sensory homunculus – the brain’s detailed map of body parts like fingers, toes, arms, and legs- show that when more blood flows to the area representing the fingertip, people more readily perceive a light tap on the finger. This suggests that blood affects the function of this brain region and that information about blood flow can predict future brain activity. This finding does not undermine prior studies, but adds another, richer layer to their interpretation and makes fMRI an even more useful tool than it already is.

How could blood flow affect brain activity? Blood contains diffusible factors that could leak out of vessels to affect neural activity, and changes to blood volume could affect the concentration of these factors. Also, neurons and support cells called glia may react to the mechanical forces of blood vessels expanding and contracting. In addition, blood influences the temperature of brain tissue, which affects neural activity.

To Moore’s knowledge, the Hemo-Neural Hypothesis offers an entirely new way of looking at the brain. “No one ever includes blood flow in models of information processing in the brain,” he asserts. One historical exception is the philosopher Aristotle, who thought the circulatory system was responsible for thoughts and emotions. Perhaps the ancient Greeks were on to something.

This work was funded by Thomas F. Peterson, the Mitsui Foundation and the McGovern Institute for Brain Research at MIT.

Source: MIT

Posted by Robert Karl Stonjek at the Mind-Brain Yahoo discussion group

Alfredo Pereira Jr.

Nature Neuroscience – 10, 1230 – 1232 (2007)
doi:10.1038/nn1007-1230

The ins and outs of fMRI signals
Nikos K Logothetis

Perhaps because a picture is worth a thousand words, images from functional imaging studies seem particularly revealing of the neural mechanisms behind our thoughts and actions. Despite this perception, neuroimaging techniques, such as invasive quantitative autoradiography, positron emission tomography, optical imaging of intrinsic signals and functional magnetic resonance imaging (fMRI), use hemodynamic responses as surrogates for neural function. The blood oxygen level–dependent (BOLD) contrast in fMRI depends primarily on blood oxygenation, which in turn reflects metabolic activity in the tissues. Although BOLD fMRI has helped to address important questions about our cognitive capacities and their relationships to cortical activity, we still lack a clear understanding of the neurometabolic and neurovascular coupling underlying BOLD signals. This information is necessary for a sound interpretation of fMRI signals, as BOLD fMRI reflects a complex interplay of changes in cerebral blood flow, cerebral blood volume and blood oxygenation. There are many open questions. What kind of neural activity draws most of the metabolic energy? Which cell types generate it? What is the dynamic link between such activity and energy demands? What are the exact processes coupling the supply of and demand for energy in the brain tissues? A study in this issue addresses the first of these questions.

In their study, Viswanathan and Freeman used a dual microelectrode to conduct simultaneous and colocalized measurements of oxygen partial pressure and electrical activity at a high spatio-temporal resolution in the cat visual cortex. Their electrical measurements assessed both local field potentials (LFPs), which represent the integrated local dendritic events in an area, and action potentials, which depend on the activity of projection neurons. Their experiments revealed a strong coupling between LFPs and changes in tissue oxygen concentration. This important finding suggests that perisynaptic activity places the greatest demands on metabolic energy. These results also imply that fMRI signals most likely reflect the input and intracortical processing in the mapped brain site, rather than its output instantiated in the firing of the projection neurons. In this context, ‘perisynaptic’ captures the classical events of synaptic transmission, with its respective population of excitatory or inhibitory postsynaptic potentials, as well as a number of integrative processes, including somatic and dendritic spikes with their ensuing after-potentials and voltage-dependent membrane oscillations.

(...)

Published online: 26 September 2007
doi:10.1038/news070924-5 Study links migratory navigation systems in the eyes and the brain.

Katharine Sanderson

Warblers’ eyes connect up to the magnetic navigation system in the brain.

How do migrating birds perceive which way is north? Research now points to the idea that they actually ‘see’ the Earth’s magnetic fields, rather than feeling or sensing them in some other way.

Previous work has suggested that the Earth’s magnetic field might act on the sensitivity of a migratory bird’s eye, so that sight might be involved in finding magnetic north. Now researchers have firmed that up with evidence that molecules in the eyes of migratory birds are connected to the part of the brain that guides their direction of flight.

Dominik Heyers, at the University of Oldenburg, Germany, and colleagues injected migratory garden warblers (Sylvia borin) with a tracer capable of travelling along neuronal fibres along with nerve signals. They injected one tracer into the part of the forebrain known to be the only active area when birds orient themselves (known as Cluster N), and a different tracer into the retina.

After a bird experienced a desire to migrate, both tracers ended up in the same place, the researchers report in the Public Library of Science One1 — a part of the thalamus responsible for vision.

This anatomical link strongly supports the notion that the birds probably experience magnetic fields as a visual sensation, say the researchers.

Northern black spot

It has previously been suggested that proteins called cryptochromes in the eyes of migratory birds might play a role in their compass-like ability.

The idea is that these cryptochromes might be sensitive to the electronic state of radical pairs. These pairs can exist as singlet or triplet states, and the relative proportions of these states is in turn influenced by the orientation of the molecules in the eye relative to the Earth’s magnetic field (or any other magnetic field that the birds are exposed to).

“This means that if a bird looks in a certain direction, the magnetic north might be seen as a dark spot,” says Heyers, although he adds that the precise way the birds see that magnetic field is subject to a bit of guess work: “we cannot ask [the birds] how they see it.”

Beaks and eyes

Heyers’s work showing a connection between the retina and Cluster N is a “great result”, says Miriam Liedvogel, who studies migration at the University of Oxford, UK. But in her opinion it isn’t enough to prove the hypothesis that birds can ‘see’ magnetic fields, she adds. She’d like to see experiments where changing the magnetic field is conclusively shown to change neuronal activity in the thalamus, she says.

And this will not to be the end of the story of how birds find their way. Other work has shown that migratory birds also have magnetic crystals in their beaks that are involved in navigation. Heyers thinks that the two systems probably exist to complement each other, with the beak being used to measure the strength of magnetic field as a kind of map, and the cryptochromes in the eyes acting as a compass.

References Heyers, D., Manns, M., Luksch, H., Güntürkün, O. & Mouritsen, H. PLoS One (2007).

Story from news@nature.com: http://news.nature.com//news/2007/070924/070924-5.html

A molecular “recycling plant” permits nerve cells in the brain to carry out two seemingly contradictory functions – changeable enough to record new experiences, yet permanent enough to maintain these memories over time.

The discovery of this molecular recycling plant, detailed in a study appearing early online Sept. 19 in the journal Neuron, provides new insights into how the basic units of learning and memory function. Individual memories are “burned onto” hundreds of receptors that are constantly in motion around nerve synapses – gaps between individual nerve cells crucial for signals to travel throughout the brain.

According to the study’s leader, Duke University Medical Center neurobiologist Michael Ehlers, M.D., Ph.D., these receptors are constantly moving around the synapse and often times they disappear or escape. Ehlers discovered that a specific set of molecules catch these elusive receptors, take them to the recycling plant where they are reprocessed and returned to the synapse intact.

“These receptors constantly escape the synapse and are in a perpetual state of recycling,” said Ehlers, who is also a Howard Hughes Medical Institute investigator. “This process occurs on a time scale of minutes or hours, so the acquisition of new neurotransmitter receptors and their recycling is an on-going process. Memory loss may result from receptors escaping from the synapse.”

All this activity takes place on millions of tiny “nubs,” or protrusions in the synapses known as dendritic spines. The recycling plants are located within the body of these dendritic spines.

“We believe that the existence of this recycling ability explains in part how individual dendritic spines retain their unique identity amidst this constant molecular turnover,” Ehlers said. “The system is simultaneously dynamic and stable.”

While these findings should be able to help neurobiologists as they attempt to understand the molecular foundations of learning and memory, Ehlers believes that this knowledge could also be helpful in explaining what happens in certain neurological disorders, such as Alzheimer’s disease, schizophrenia, or learning disorders like autism.

For example, it appears that in animal models of the early phases of Alzheimer’s disease, often before any symptoms become apparent, the dendritic spines gradually lose their ability to transport and recycle the receptors.

“If the receptors don’t get recycled, you see a gradual loss