I want to thank Alfredo (and Nathan Munn) for co-editing this blog, and creating a Forum. I will link to the Forum as soon as possible.

Dr. Pereira makes the case for astrocytes in the brain as substrates of consciousness, and specifically for a “neuronal global workspace”. (See the Glossary on Scientific Consciousness Terminology, also soon to be posted here.) Astrocytes are very interesting little critters. Until recently it was thought that astrocytes (literally, ‘star-shaped’ cells, but often taken to be synonymous with neuroglia) were merely neuronal support cells. They are that, but they also conduct information processing, as it now appears. However, I do not believe that the evidence currently supports a DISTINCTIVE role for astrocytes in supporting conscious (as opposed to unconscious or less conscious) brain events.

Here’s why.

1. Astrocytes are too widely distributed. Conscious contents (at least in humans) are primarily a function of cortex - obviously in interaction with subcortical structures. We know that because (a) specific cortical lesions lead to specific deficits in conscious, but not necessarily unconscious, cognitions. In contrast, (b) subcortical lesions, like bilateral cerebellar lesions, may not affect conscious contents or even the conscious state at all; © stimulation of cortex, but not subcortex, leads to specific conscious events in waking subjects (classically in Wilder Penfield’s neurosurgical patients); (d) loss of the conscious STATE involves, not a drop in neuronal firing, but a drop in fast and long-distance interactions among neurons and neuronal populations. There’s a lot more evidence for DISTINCTIVE conscious, but not unconscious brain events, but those points are basic.

2. Note that any adequate hypothesis about the brain basis of consciousness must account for the DIFFERENTIAL properties of conscious, but not unconscious, brain events.

3. Astrocytes do not differentially account for conscious, but not unconscious brain events.

Astrocytes are widely distributed in the brain, including the cerebellum. Yet a bilateral loss of the cerebellum does not lead to a loss of conscious contents or state. I believe (but would like a reference) that there are no brain regions that lack astrocytes - they are really basic.

(Astrocytes are the reason for the famous “white matter” of the brain, the huge body of white tissue that can be seen with the naked eye when a mammalian brain is dissected. The white coloring is due to high lipid content of astrocytes, which wrap around all the nerve tracts, both supporting and protecting neuronal signaling. Because neuronal cell bodies in the surface layers of cortex are not surrounded by astrocytes, they appear greyish to the naked eye. There is not question that astrocytes are vital. The only question is whether they distinctively support conscious brain events.)

4. Dr. Pereira points out that astrocytes are especially plentiful in Layer I of the cortex, which is often called a dendritic “feltwork,” so that it is the dendrites (input branches of neurons) that make up Layer I, along with glial cells. That is fascinating, of course, but it does not prove the claim that astrocytes are differentially associated with conscious experiences. Layer I contains numerous dendro-dendritic connections, so much so that it is believed that Layer I may itself be a major information processing highway. (Normally we would look to axonal-somatic synapses, as in the major white matter pathways.) But there is no evidence that I know of that Layer I is DIFFERENTIALLY associated with conscious, rather than unconscious, processes.

5. To test these hypotheses properly one would have to study knockout mice, for example, if one could vary the number of astrocytes without impairing vital functions.

6. Assessing conscious experiences in animals, using closely analogous measures.

In humans we assess conscious experiences behaviorally by means of accurate, voluntary report, the evidentiary basis for all of psychophysics for the last two centuries. That is an excellent method, and in animals the analogous method is “match to sample”, essentially a way of asking other animals whether some stimulus S1 matches some previous or simultaneous stimulus S2. Using operant conditioning one can obtain voluntary reports that are methodologically equivalent to human voluntary reports. Animal experiments are therefore directly relevant to the question of human conscious experience.

6. We start from humans.

Arguably, humans are our “criterial species” for studying consciousness, just as pigeons might be the criterion species for studying bird flight. Once we understand such basic biological phenomena in one species we can carefully look for homologies in others. That line of standard biological reasoning strongly suggests that mammals (characterized by rich, thalamocortical systems in the core brain) are conscious. Comparative biologists are exploring the possibility of wider homologies, among birds, reptiles, and recently, even cephalopods.

However, using the most conservative criterion of direct anatomical and physiological homologies, there is no current reason to doubt that non-human mammals are at least perceptually conscious.

7. Consciousness appears to be widely conserved in the animal kingdom.

Dr. Pereira seems to suggest that humans are conscious, but that perhaps other mammals may not be. That is always possible, of course, because we only have “atheoretical evidence” at this point in the scientific study of consciousness. That is, we do not yet have a shared theoretical basis for understanding consciousness (though we have some well-developed hypotheses). Until chemistry provided an understanding of O2/CO2 exchange via alveoli in the lungs, there was no theoretical basis for understanding that lungs (and gills) were vital for animal metabolism. However, Aristotle was still able to make an atheoretical case for lungs and breathing as highly conserved animal features, with a lot of empirical evidence.

8. Theoretically-based and atheoretical arguments by homology.

Dr. Pereira’s hypothesis is therefore not disprovable on theoretical grounds. But the available evidence, as far as I can tell, does not support the hypothesis.

Coming Soon: Current candidates for a brain basis for conscious experience.

I will write an entry soon on what appear to be some plausible brain substrates for conscious experiences. Again, astrocytes are surely involved in some way - they are just not DIFFERENTIALLY involved in conscious, compared to non-conscious brain events.

BJB

I am planning to keep this blog running permanently, updating it on a weekly basis. There is now a HUGE, active scientific and medical literature, very fascination. This is the first time in the history of science - believe it or not - that there is a coherent, international, multidisciplinary effort to understand the conscious brain - and everything that brings along with it. Which is almost everything in the human arts, music, philosophy, craftsmanship, culture, religion, atheism, and the like. Fortunately our current science is very focused on a smaller number of issues.

1. We have a running advanced web seminar now at CONSEMINAR

Feel free to explore the site. Downloads are for strictly limited educational purposes only. You are welcome to email me at baars@nsi.edu if you have any questions.

I’ve found it hard to keep this blog going, but I know that a constant flow of interesting Posts is needed. So I am delighted to welcome Dr. Alfredo Pereira, Jr., from Brazil, and Dr. Nathan Munn from the University of Montana. They will help keep things lively.

It’s important to remember that we have a constant flow of scientific articles bearing on consciousness, volition, and self, the three core ideas for this blog. Plus anything else we think about. We will also link this blog to a little Web Village on Conscious Brains. So there will be both News and Readers/Commentators, we hope and trust.

BJB

Alfredo and Nathan - please feel free to Post as the urge takes you…

IS IT QUANTUM? - Reply from Baars :https://sites.google.com/site/conseminar/url/to/link/to (for scientific and teaching materials on consciousness and the brain).

Thank you both for your comments.

I am going to be posting weekly - apologies for allowing this good start to languish for so long! I think the answer is to use it regularly, and then to link the entries to other online activities, including my own. I will also be updating my Wikipedia entry and websites.

In answer to Dr. Fontoira in-depth case for a quantum notion of consciousness, this idea has been hotly discussed. It continues to be, with some good scientists finding it attractive, but the majority being skeptical.

I count myself as a skeptic, but I hope an openminded one.

Here are the reasons to be skeptical about QM notions of consciousness.

1. Are there unconscious brain events?

This used to be hotly debated in psychology and brain science. It is not any longer. The evidence for unconscious brain processes is simply overwhelming. You must simply look at the literature. I discuss it in Baars & Gage, Cognition, Brain & Consciousness: An Introduction to Cognitive Science (2007, Elsevier/ Academic Press), and in my more introductory book, from Oxford 1997, “In the Theater of Consciousness: The Workspace of the Mind.”

But you can simply search in PubMed or Google Scholar under “unconscious brain” and that will bring up multiple research articles. To simplify radically, our brains are unconscious of

• memories while they are stored, vast body of information*;

• highly practiced automatic skills (traditionally called HABITS) associated with basal ganglia and cerebellum*;

• major aspects of sensory systems, such as the “dorsal stream” of vision*;

• motivationally excluded materials, which used to be extremely controversial in science, but it is now clear on the evidence that people do a vast amount of selective control of what they will be conscious of, and correspondingly, the things they avoid being conscious of*;

• broadly speaking, subcortical, spinal and peripheral neuronal processes*.

2. QM AND CONSCIOUSNESS.

There are several proposals that consciousness depends upon quantum-mechanical processes. Roger Penrose and Stuart Hameroff are a famous source of that hypothesis. There are others. The basic counterarguments are these.

a. The burden of proof is on the proposer in science, and there is currently no peruasisve evidence FOR the QM notion.

b. QM is taken to be explanatory of the so-called “Hard Problem” in philosophy of consciousness, which arguably does not exist.

Thus Gerald M. Edelman has argued that it does not, as did Francis Crick and his co-author, Christof Koch.

c. IF QM somehow explains the Hard Problem (which is the old mind-body problem, i.e., how does conscious experience relate to physical nature, the body and the brain?), then we are trying to explain one unknown by another unknown.

Quantum mysteries are taken to account for Mind-Body mysteries, which does not look like a step in the right direction. Or as my favorite science parodist Terry Pratchett might put it, “Let’s call it Quantum!” is NOT an explanation.

d. Finally, and most specifically, QM phenomena are studied at extremes of temperature and spatial resolution that are not routinely observed in the brain.

That goes especially for temperature. QM phenomena are found near 0 degrees Kelvin. Physiological temperatures are way above that.

So - I don’t really think there are many closed issues in science.

We used to think that DNA was a completely protected molecule, and that something like “epigenetics” wasn’t possible. That was wrong.

We used to think all kinds of things in science that we now know better. (We hope!).

So I would not exclude QM accounts of consciousness in principle, forever and ever. We are inductivists, we wait for evidence.

I would say there is no evidence I’ve seen at this time that appears to be persuasive, thought Prof. Stuart Hameroff has some very clever ideas on QM in nerve cells.

Also, there are some strong counterarguments. If we ever find body-temperature QM phenomena, we’ll have to take another look!

The very word “consciousness” used to be something of a taboo in the scientific world. But today a growing number of well-known scientists have joined the quest to understand it. The list includes Nobelist Gerald Edelman, Christof Koch, Rodolfo Llinas, Antonio Damasio, and many others. A specialized journal has been running for a decade-and-a-half. A scientific organization, the Association for the Scientific Study of Consciousness , has been holding international conferences for almost as long. Mainstream journals in psychology, brain science, neurology and neighboring fields have joined in.

Twelve years ago Francis Crick published an introductory article in Nature, saying that “the problem of the neural basis of consciousness looks ever more tractable as neurobiologists delve into the process of visual perception”. Crick spent the last decades of his productive life pursuing the notoriously tricky problem of the conscious brain. It was Crick who strongly encouraged pioneering studies on visual consciousness, notably by Nikos Logothetis and his team , using binocular rivalry in macaque monkeys. That continues to be a very productive stream of work today.

Binocular rivalry is an attractive paradigm for the following reason. Try this experiment: Hold one pencil (or another small object) in front of your right eye, and an identical pencil in front of your left eye, both at the same distance, a few inches from each eye. Now see if you can “fuse” the two identical pencils into a single conscious pencil. That simulates binocular vision in nature: We constantly fuse nearly identical views of the same objects in the world around us. We do it so smoothly that we rarely even realize which of our two separate eyes is the dominant or “conscious” one.

But now try a variation. Hold a pencil in front of one eye, and a pen with a different color and shape in front of the other. Do they fuse into a single conscious percept? Not if the experiment is done carefully. The two images will compete with each other if they cannot be perceptually fused. When two images compete, one tends to be conscious for some time, while the other is suppressed. What happens to the suppressed input? We have good evidence that the unconscious stimulus is still processed to quite a high level in the brain.

Thus the brain receives two nearly identical stimuli, one of which is conscious, the other unconscious. We can now ask the question, “What is the difference between two very similar brain events when only one is reportable as conscious?” Binocular rivalry is the double-slit experiment in the experimental study of consciousness.
Experiments like this have put visual consciousness on the map. Many other methods have now been added. But it’s not just visual awareness alone; we can study consciousness as a state via sleep versus waking, coma and general anesthesia. Or we can study medical conditions like narcolepsy, and the brain chemistry of new “wakefulness” drugs like provigil. We can explore profound puzzles like “blindsight,” the ability of patients with damage to the first visual cortex to spot certain visual events and still hotly deny that they ever really saw them. Other patients lack emotional feelings, or bodily sensations, or the ability to see motion or certain kinds of objects. There are dozens of conditions that dissociate conscious from unconscious brain events. Those natural and experimental dissociations make it possible to study consciousness “as such.”

Today, a PubMed search for “consciousness” brings up 23,142 articles. Not all of them are about consciousness as the major focus, but many are. Then there are the scientific synonyms like “explicit” vs. “implicit cognition,” “supra-” vs. “subliminal stimulation,” “aware” vs. “unaware” conditions and many more. As Science magazine wrote in its 2005 anniverary issue, the “biological basis of consciousness” is now often considered one of the top unsolved problems in science. Unsolved, but not necessarily unsolvable.

Consciousness is back, after a long absence .

This blog - A Conscious Brain - turns the spotlight on a number of recent discoveries and ideas, in a really fun and fast-moving field of science. There is now marked empirical progress, and theories are emerging. It’s still early days; when it comes to the conscious brain we may be living in the early age of science. Yes, we are collecting better evidence, but without a Newton or Copernicus to show how it makes sense. Yet consciousness science is finally back on track. New findings appear every month, testable issues are debated, and normal, healthy science is beginning to grow.

We don’t know that human (or animal) consciousness can ever be understood — but we’ll never know unless we try. That’s what A Conscious Brain is about.