Meetings

Meeting 5

note taker: E.I., September 16, 2007 4-6pm

Powerpoint Presentation

DISCUSSION (Following C. Suchy-Dicey presentation

[Q = Question, A = Answer, C = Comment] 

Q: How does the Sperling experiment illustrate Block's point?

A: It shows that although access is limited to four pieces of information, you can have consciousness of larger than four entities.  i.e. consciousness overflows access.  

Q: If limit of access is four, and I can be conscious of more than four entities, consciousness must be in a separate place in the brain than access?

A: Not necessarily.  Consciousness overflows access/working memory.  And it seems as if consciousness and working memory are in different part of the brain.  Thus, consciousness and access are separable.  But evidence for the second claim (that they are in different parts of the brain) is contentious.  Many neuroscience studies have showed that both the sensory cortex and frontal lobe need to be activated for consciousness.

Q: Is that Block's view?

A. No, Block says that the frontal lobe is not necessary.   

Q: Access consciousness can be a process on top of phenomenal consciousness.  Analogue visual representations can be stored in, for example, the visual cortex.  But doesn't extra processing in other parts of the cortex seem to be required for the phenomenal consciousness?

A: The key perhaps is memory in the sensory cortex.  But are we "experiencing" this memory?  Block will say you're experiencing everything in the brain, but you're not accessing everything.

C: Neuroscience has shown us that there are many spontaneous activities in the brain (e.g. spikes in the auditory neurons that are in theory "audible") that we are not aware of.   

Q: Regarding chunking, how can we know what constitutes/will constitute "1 bit" of information?  If I have four bits of information, but I can break each of them down to four bits, don't I actually have sixteen bits of information?  How can distinct entities be articulated?

A: The mechanics of experience are difficult to tease apart. It seems that what comprises a chunk depends on how your frontal cortex treats the information. There may be an upper and lower limit, but research in this area continues.  

Q: If Sperling did showed 3x5 or 5x3 letters (instead of 3x4), would the number of entities reported been different from four?

A: No.  The experiment has been conducted in many ways, and whatever way the information is presented, the subject can only report back four.  (and 7+/- 2 for verbal memory)  

Q: We never experience our environment in 50msec spikes.  I wonder how pertinent the Sperling experiment is to (what exactly it can say about) the way in which we process information about this world.  50msec presentation doesn't bring up a strong image (image will be decaying immediately).  If shown longer, it might be more than four.  The regenerative loop reverberatory pattern may account for consciousness.

A: Yes.  Consciousness may be better correlated to types of relationships (or recurring functional patterns) of the brain, as opposed to an area of the brain. But Block will not deny that that kind of loop is responsible, he will just say that the loop exists within the sensory cortex as well.

C. I suppose it's whether you perceive consciousness to exist in a global workspace, or in local ones.   

Q: "Access"--can it be shown at the propositional level?  Or is it at the pre-propositional level?

A: In this context, access consciousness is taken to be at the pre-propositional level.  It may be that criticism of this position claims that something like propositional access is required for chunking, but that cannot possibly be required for all conscious experience. This needs to be worked on.  

Q: "Conscious when one can report"--this is clear.  However, "Conscious when there is access"...this is not as clear. *Who* or "what subject" has access to what is supposed to be something 
Block claims one is conscious of?  What does Block presume here, and what do you think?

A: I think Block, as an identity theorist, would say that the subject is located in the mind itself.  Access is a psychology term.  In brain science terms, it might be conceived of as the "flow of information from one part of the brain to another".

Q: So do you mean something like: Brain comes to a structural similarity with the world, and access is just touching that structure?

A: The brain is touching the world and access is touching our experience of the world. The phenomenological language is not necessarily collapsible to the scientific language.  I think that access refers to introspective access.

Q: But how can that be described?

C: The position of identity theory would be self-defeating if “access” is taken to be constitutive of being conscious, because then we would either (i) have no correlates of the transcendental or phenomenological mind which has access to something, or (ii) take some special neuron architecture as the neural correlates of the mind which has access to
other part of the brain. But the latter is only a disguised version of substance dualism: not that some special chemical elements plays the role of mind, but some special neural structure would play the role of mind.

C: Perhaps the explanatory gap is as follows:  Consciousness can be identified as sensory cortex activity.  Access can be identified as neural stimulation between X & Y.
 

Q: Is the sensory cortex active when I'm [consciously] thinking about non-sensory things? If so, couldn't this be proof that consciousness does not exist in the sensory cortex, as Block presumes?

A: Block is focusing only on the consciousness involving sensation, that is, phenomenal consciousness. Non-sensational "thinking" is not considered in the same category as the consciousness he is trying to argue for the existence in the sensory cortex. It is also unclear whether or not we can actually "think" without any visual/sensory involvement.

C: But Helen Keller seemed to be able to conjure information without complete sensory input. We also know that our senses can be extended beyond our organs, for example, when we hold a pen, we can "sense" things with the pen as if it became an extension of out hand.

A: But Helen Keller did have some sensory capacity. In addition, her sensory cortex for her modalities was likely to be in tact. This could account for her capacity to be "conscious" of entities without physical input from the organs.Also, it is enough that there is sensory experience that does not involve access to prove Block's point.   

Q: Previous theories equated consciousness with reportability. Now, consciousness is equated with processing at the neural correlates. And Block wants to claim that if you have a bit more (brain processing) than the neural correlates, you can have reportability. But who is reporting what? The brain processing is reporting the brain processing? And what accounts for whether the conscious state can be reported to the reporting state? More processing? Do you agree with me that Block's notion of "access" is confusing?

A: Yes.

Q: The idea of chunking seemed to appeal to memory/conceptualization. But if that is the case, isn't it true that the Sperling experiment doesn't involve chunking because memory and concepts can't come into play due to its experimental design?

A: There is a difference between visual and verbal memory. The "CIAFBA" example was verbal, and that kind of memory is encoded in the hippocampus, thus most likely involving further processing (with memory and concepts). The visual memory involved in the Sperling experiment could be encoded in a different kind of "cellular memory" that has to do directly with the tendencies of the cells in the e.g. visual cortex. The visual cortex cells, through genetics and experience, are/become connected in various ways such that it will 'tend' to receive and process information in a particular way. It is this kind of memory, intrinsic to the structure of the sensory cortex, that could be involved in the chunking of the Sperling experiment. Although it also used letters, and so could be verbal in part.  

Q: Isn't your last story (about the patient who was totally locked in, until he became able to) supportive of Block's view that consciousness is possible without reports?