CONSCIOUSNESS Phil/Psych 256 Chris Eliasmith
The C Word One main difficulty with consciousness is defining what we are talking about: Do we mean awareness (e.g., awake vs. asleep)? Qualia (what-it-is-like)? Noticeability (i.e. conscious as opposed to sub-conscious)? Introspection (reporting on your internal states)? Self-awareness (known who/what you are; self vs. other)? These various meanings make sweeping claims about consciousness difficult to verify or adjudicate.
A Definition Main Entry: con scious ness (noun) Date: 1632 1 a : the quality or state of being aware especially of something within oneself b : the state or fact of being conscious of an external object, state, or fact c : AWARENESS ; especially : concern for some social or political cause 2 : the state of being characterized by sensation, emotion, volition, and thought : MIND 3 : the totality of conscious states of an individual 4 : the normal state of conscious life <regained consciousness> 5 : the upper level of mental life of which the person is aware as contrasted with unconscious processes That explains the confusion
Consciousness and Science An example (Sleep) Experiments regarding the patterns of EEG changes during sleep and waking have shown that specific kinds of wave activity can be associated with certain kinds of unconscious (i.e., sleeping) states. There are different patterns for deep sleep vs. REM sleep, so different degrees (or types) of unconsciousness are apparent. The neurobiology of sleep literature is huge, but there are many unresolved issues, and the mechanisms of sleep have not been pinned down. One thing is clear in this case, is that understanding consciousness in this sense is closely related to understanding how the brain works. There is little question that learning about the brain can teach us something about consciousness. But it's not clear whether or not the NCC is all there is to consciousness
Consciousness Challenge In philosophy, the challenge to cog sci is usually framed w.r.t qualia 'Qualia' is a name for the 'what it is like' of sensory experience, e.g. what it's like to see red, or a square. The first person, subjective experience of sensory states. These sorts of phenomena are essentially ignored by past CRUM approaches The sleep example shows that the problem is more general
Consciousness Challenge Thagard suggests we can't deny existence of qualia as we can deny the existence of caloric because these are the experiences we all know we have. However, many have denied qualia (e.g. Dennett) but not the phenomena, just their classification as a kind of 'thing' We don't have to deny experiences to deny that they should be unified in a theoretical framework (see, e.g. heat, which is identical to at least 4 very different processes). Thagard is right, however, if we take him to simply mean that we can't deny that there are first-person experiences.
Consciousness Challenge (cont.) Just as for emotion Thagard seems to suggest that we might have to supplement CRUM. We need to expand CRUM because the contents of conscious representations might be different and suggest new computations. We need to supplement CRUM because biological considerations will introduce novel insights that are incompatible with CRUM Again, only expansion seems persuasive for the same reasons as in the emotion case.
Crick and Koch Crick and Koch break the problem of qualia into subproblems that include: 1. What is consciousness for? 2. Why are some aspects of subjective experience impossible to convey to others? They answer these questions by claiming that: 1. (Visual) consciousness is for producing the best current interpretation of the visual scene to guide voluntary action 2. Representations are constantly recoded, and recoding from visual to motor representations (for speech) results in representations that are related (but not identical) They also think that there are two problems they can't yet answer: 3. How do we experience anything at all? and 4. What leads to a particular conscious experience?
consciousness Social importance Relative position Sights Sounds
consciousness Broca s area recoding Vision monkey
Neural Correlate of Consciousness NCC: Make the problem of consciousness scientifically addressable (NCC). Want to know which neurons are correlated to conscious experience, why they are correlated and others are not, and what kinds of special properties they have. Answering these scientific questions is sufficient. They seem to assume only that some extensions of CRUM will have to be made. Problems with NCC: Philosophers have often argued that finding correlations between brain states and phenomena isn't enough for explaining consciousness. Just because there is a correlation doesn't mean you have said what the relation between brain states and consciousness is. Furthermore, they have argued that because consciousness is subjective and science is objective, science necessarily can't explain consciousness (e.g. Nagel and Chalmers). This leads to a kind of dualism.
Neural Correlate of Consciousness Responses to problems: Like 'heat', 'consciousness' is supposed to be identical to some (perhaps independent) physical states. Just as we don't think of heat as being caused by the motion of particles, we shouldn't think of consciousness as being caused by brain states Ockham's razor says we should prefer the simpler theory, i.e. an identity The subjective/objective distinction is simply two ways of accessing the same phenomena. This is sometimes called a dual-access theory (e.g., Schlick).
NCC Experiments C&K describe the kinds of experiments they think are relevant to understanding consciousness. Blindsight (see what it's like on the web): When large portions of V1, primary visual cortex, are destroyed, patients report complete blindness; i.e. they are not visually conscious. However, on forced choice tasks (where they must answer yes or no, left or right, etc.) they perform far better than chance for locating objects. When objects are moving, they do quite well. If the objects move fast enough, they occasionally report vague visual experiences. C&K argue that another visual pathway (through the superior colliculus and pulvinar) is sending small amounts of visual information to the visual cortex, and that this can eventually (if strong enough a stimulation) elicit partial conscious experiences.
Blindsight
NCC Experiments Bistable percepts: This takes advantage of binocular rivalry in which the items shown to the two eyes are completely different (e.g. a face and a starburst) First one then the other percept is 'noticed' (seems to be an entirely involuntary 'switching' of percepts between the two stable states; hence bistable). Monkeys can be trained to report which of the percepts they are currently experiencing. By looking for cells that fire only when a certain percept is reported, neuroscientists can get an idea of which cells are involved in generating the subjective experience (the stimuli themselves are perfectly constant).
NCC Experiments (cont.) Unconscious action: Milner and Goodale have shown convincingly that much action is guided without subjective experience. By examining the precise kinds of damage and the reports of patients, it may be possible to use this to discriminate between unconscious and conscious visual information processing. Patients with ventral damage can catch a ball, but don't have a normal experience of a round object coming at them (and can interact with but not report the angle of a slot).
Bistable Percepts?
NCC Hypothesis Given this data, C&K think that frontal areas are where the NCC is most likely to be found This is where visual information can be used to control voluntary action. Prediction: a person with no frontal areas wouldn't have conscious visual experience. This hasn't been confirmed, but monkeys who have had large frontal lesions act completely blind. As well, fmri of blindsight patients shows that frontal areas (46 & 47) are active only when the patients report a 'slight' visual experience. Other NCC suggestions: Thalamus (Sejnowski) Cortical Waves (Llinas) 40Hz oscillations (Crick and Koch, earlier)