Brain Physiology, Cognition and Consciousness: topic
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The "Binding Phenomenon" - only apparent?
Hans Ricke
Wednesday, 10 October 2007 06:37 UTC
I started discussing this topic with Alfredo on PSYCHE, so maybe it is a good idea to start a thread about this here too.
When I first came upon this matter through Jonathan Edwards, I felt that is a good starting point for cognition science, because here we face one of the basic phenomena of consciousness. We all experience consciousness as if bound.
This led especially in Germany as far as I know to the view that y-synchrony is a strong candidate for a correlate to consciousness because it shows different consciousness-related parts of the brain working at the same time – synchronized.
I took the view for real first, but lately developed some doubt that indeed the phenomenon may be just apparent. That would lead to the idea that the different parts of conscious content only appear to be bound, when in real reality the happen at almost the same time. The would not be bound spacially nor if we look more closely even timingwise.
So audition could become conscious elsewhere than vision or thought.
So consciousness could very well not be bound. One of the lines of thought why I doubt doubt consciousness can at all be bound is timing issues.
There are obviously ideas that incoming signals are transformed via chemical intracellular processes. This is probably right, but chemical processes require time. Time that adds up from cell to cell that is involved in the whole process that e.g. starts in a retina cell that is hit by a ray of light. I do not know how well these timing issues are already cleared up by neuroscience, but my hypothesis is that, given that many cells are involved having chemical processes going on, time is to short between an incoming signal and when we become conscious of what we see.
This leads to the idea that there must be at least two ways how the body deals with incoming signals: 1. slow, involving chemical processes, many cells, deconstructing of incoming information, analyzing information, reconstructing information.
2. fast, not involving chemical processes, less cells, leaving incoming information as is.
The first way is a model for learning how to perceive, the second way is a model for primary perception and also immediate perception.
What I would be most grateful about would be information about what has been already found regarding the timing of sensory processes.
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Dear Hans:
Many thanks for bringing this discussion to BPCC!
I agree that the timing is crucial, while arguing that an analysis of experimental data about perceptual processing in the brain will lead to the conclusion that binding is real.
Will Jonathan Edwards join us in this group? He is essential in this discussion.
Below I paste the summary of recent publication with important data for our discussion.Best Regards,
Alfredo
Brain Dynamics Underlying the Nonlinear Threshold for Access to Consciousness
Antoine Del Cul, Sylvain Baillet, Stanislas DehaeneWhen a flashed stimulus is followed by a backward mask, subjects fail to perceive it unless the target-mask interval exceeds a threshold duration of about 50 ms. Models of conscious access postulate that this threshold is associated with the time needed to establish sustained activity in recurrent cortical loops, but the brain areas involved and their timing remain debated. We used high-density recordings of event-related potentials (ERPs) and cortical source reconstruction to assess the time course of human brain activity evoked by masked stimuli and to determine neural events during which brain activity correlates with conscious reports. Target-mask stimulus onset asynchrony (SOA) was varied in small steps, allowing us to ask which ERP events show the characteristic nonlinear dependence with SOA seen in subjective and objective reports. The results separate distinct stages in mask-target interactions, indicating that a considerable amount of subliminal processing can occur early on in the occipito-temporal pathway (270 ms) and highly distributed fronto-parieto-temporal activation as a correlate of conscious reportability.
Introduction
One of the most obvious and yet unexplained properties of conscious perception is the existence of a threshold for conscious access: when a stimulus is flashed and followed by a backward mask, subjects do not report perceiving it until the target-mask interval exceeds a threshold duration. Below-threshold-or “subliminal”-stimuli receive complex perceptual and even semantic processing , but for an unknown reason, these processes remain inaccessible to consciousness. Understanding the neural mechanisms that distinguish such conscious and nonconscious processes remains a crucial issue in cognitive neuroscience. We used high-density recordings of event-related potentials (ERPs) to ask several questions: (1) What sequence of activations is evoked by subliminal masked stimuli? (2) What additional sequence of brain events leads a stimulus to cross the threshold for conscious reportability? (3) At what time does this access to conscious report occur?Existing models of conscious access differ markedly with respect to the brain areas involved (posterior versus anterior) and the timing of their activation (early versus late). A first category of model views conscious visual perception as a phenomenon localized to posterior brain areas, and whose contents are determined by the pattern of neuronal activity in early visual and/or occipito-temporal areas. According to these proposals, the threshold for conscious perception during masking should be determined solely within the visual cortex, either within a single area or due to short-range recurrent interactions among posterior occipito-temporal regions . As far as timing is concerned, some authors have proposed that conscious perception is already detectable in the ascending, feedforward activation evoked as early as 100 ms after stimulus presentation. For others, visual consciousness is not associated with feedforward visual activation, but requires a subsequent period of “localized recurrent processing” , still relatively early and confined to posterior occipito-temporal brain systems. Electrophysiological recording in macaque monkeys during masking suggest a peak effect of recurrent interactions in area V1 around 100-140 ms after stimulus presentation, and intracranial human recordings suggest that category-specific ventral occipito-temporal cortices are already strongly activated by 150-200 ms, although extension to more anterior regions and reverberation effects can extend for much longer (290-700 ms). Thus, although predictions concerning timing are less precise, this category of models would predict that subjective reports of conscious perception should correlate with posterior and relatively early brain events.
Source: PLoS Biology [Open Access]:
http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0050260 -
Just a quick question: what was the exact experimental situation? What was used as a stimulus and what was used to mask it? How is the the target-mask interval to be understood?
Unfortunately the link you gave is incomplete.
Best
Hans -
Dear Hans:
I am sorry for my delay to answer your message and for the incomplete link.
In order to get the paper, please click here
If it does not open, I will e-mail it privately.Best Regards,
Alfredo
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Dear Alfredo Pereira
I have a somewhat similar question regarding the binding of time, place, and person.
We generally check and describe orientation to time, place and person. Some case reports in post head injury patients describe them to return one by one and not simultaneously. Is there any hypothesis or ideas available regarding the phenomena or the relations among time, place and person.Subrata
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Dear Hans:
A new study, published as preprint at Nature Precedings (Abstract below), brigs new light to the issue. It already received 7 votes at the site!
A new dynamic property of human consciousness
UnCheol Lee, Seunghwan Kim, Gyu-Jeong Noh, & Byung-Moon Choi
Abstract: As pointed out by William James, “the consciousness is a dynamic process, not a thing” , during which short term integration is succeeded by another differentiated neural state through the continual interplay between the environment, the body, and the brain itself. Thus, the dynamic structure underlying successive states of the brain is important for understanding human consciousness as a process. In order to investigate the dynamic property of human consciousness, we developed a new method to reconstruct a state space from electroencephalogram(EEG), in which a trajectory, reflecting states of consciousness, is constructed based on the global information integration of the brain. EEGs were obtained from 14 subjects received an intravenous bolus of propopol. Here we show that the degree of human consciousness is directly associated with the information integration capacity of gamma wave, which is significantly higher in the conscious state than in the unconscious state. And we found a new time evolutional property of human consciousness. The conscious state showed a lower dimensional dynamic process which changed to a random-like process after loss of consciousness. This characteristic dynamic property, appeared only in the gamma band, might be used as an indicator to distinguish the conscious and unconscious states and also considered as an important fact for the human consciousness model. -
Elsewhere it has been noticed that variation at the gamma level aid in detecting the real from the imagined and so we move from differentiating map and territory; a feature not common in less developed, territorial, life forms where ‘self’ and ‘territory’ are considered ‘one’.
Also see such as:
Tallon-Baudry, C. and Bertrand, O., (1999) “Oscillatory gamma activity in humans and its role in object representation” Trends Cogniti. Sci (1999) 3, 151-161
Hasselmo, M.E., (1999) “Neuromodulation : acetylcholine and memory consolidation” Trends Cognit. Sci (1999) 3, 351-359
Hutcheon, B., & Yarom, Y., (2000) “Resonance, oscillation and the intrinsic frequency preferences of neurons” Trends Neurosci. (2000) 23, 216-222
Perry, E., et al (1999) “Acetylcholine in mind: a neurotransmitter correlate of consciousness?” Trends Neurosci. (1999) 22, 273-280 -
After reading the last few paragraphs of the post directly above, is there a potential aid/cure for schizophrenia?
Thanks for responding in advance. -
Dear Dawn:
Please check our Notice on “Glutamatergic Drug for Schizophrenia!” and also my response to Avi Peled in the Forum “Energy for Conscious processing”, both in BPCC.
Best
Alfredo
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From the general perspective, the fragmenting nature of Schizophrenia corelate with the fragmenting natue of the whole as we make distinctions. If the underlying connectivity is fragile then the whole can shatter into highly differentiated parts. Since this dynamic can work across all scales so it includes operation at the level of consciousness where the fragments can take on a life of their own so to speak (!) names get mapped to parts now taken as if wholes (and so can elicit paradox that can really ‘confuse’ any controlling consciousness – and you can experience alienation to a level of rejecting ownership of those parts.)
Since the brain covers the anti-symmetric/symmetric so the brain areas often more associated with the disorder are more anti-symmetric where such covers the discrete, amplifications (positive feedback dynamics, things get exaggerated) and seeds mania and paranoia (drugs can set off these issues, in particular those associated with aminergic pathways (dopamine paths) such as cocaine and speed (amphetamines)).
The cure issues cover three forms of the disorder – the hardware form (wiring issues), the firmware form (hormone dynamics) and the software form (social/family interactions where improvements are possible through a change in context. The less improvements in different contexts the more likely the disorder is a hardware problem)
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So curing schizophrenia is a hardware problem, good – and? With that stated how do we proceed to cure my schizophrenic patients?
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