final blog entry

"Is this a shortcut?" he asked, leaning from the back-seat over the car's center console.

I couldn't tell. In ten minutes of driving - complex motor control, visio-spatial maneuvers, object recognition tasks and optic flow calculations, my mind had managed to concern itself solely with a maths problem. Nothing trivial, either; it had my complete attention. Had I been driving impaired?

I had certainly not been phenomenally conscious, but this hadn't involved concomitant loss of perception, reasoning, or motor control. This started me thinking - I know from research into attention that the brain receives much more sensory input than can be actively, or consciously addressed. Much of this information, however, is access-conscious. That is, "actively poised for direct control of reasoning, reporting, and action" (Block 1). Loss of phenomenal consciousness has been observed in patients exhibiting "Reverse Anton's Syndrome", in which patients do not realize that they aren't really blind (Hartmann et al.). These patients are at chance level when asked whether a room is dark or illuminated, but when stimuli are presented to a specific part of their visual field, they are able to report that a recognizable word or face "clicks". Block suggests that this is a kind of visual access without visual phenomenal consciousness. These affected patients generally have damage to V1 with bilateral parietal lesions, leading Milner and Goodale to suggest that phenomenal consciousness requires ventral stream activity plus attention. Subliminal studies have shown that adverse stimuli below the limen can trigger changes in galvanic skin response, indicating that the preconscious mind is able to process these and trigger sympathetic action. What, then, necessitates action by the system of attention?

A theorized cognitive construct, the executive system, is thought to be required in the control and management of other cognitive processes. Norman and Shallice have outlined several tasks which require the action of the executive system for proper function:

1. Planning and decision making.
2. Error correction and troubleshooting.
3. Situations involving novel responses.
4. Dangerous or technically difficult situations.
5. Situations involving the suppression of strong habitual response or temptation.

Since the task of driving in Nashville is so ingrained in my psyche, it seems only that a deviation from the norm would necessitate my explicit attention. If, for example, another driver were to veer into my lane, my attention would be necessary to orchestrate avoidance of the oncoming vehicle. The lag time in diverting my attention from abstract thinking to a spatial task could be injurious, in such a circumstance. But what is this attention, and even more interestingly, its conscious underpinning?

In humans, the cortex has long been thought to be a site for higher-order cognitive processes such as decision making. Crick and Koch assume that the function of the neural correlate of consciousness (NCC) is "to provide the best current interpretation of the environment---in the light of past experiences---and to make it available, for a sufficient time, to the parts of the brain which contemplate, plan, and execute voluntary motor outputs, including language" (Crick and Koch 1). They appropriate the term qualia, the subjective content associated with a conscious sensation, from philosophy, and assume its existence and physical basis in the brain. With these basic neurobiological assumptions, Crick and Koch break the problem of consciousness down into several questions:

What is the difference between neuronal activations that correlate with consciousness and those that do not? What is the character of the NCC? What can we infer about the location of neurons whose activations correlate with consciousness?

From these guiding questions, they outline several promising experimental approaches towards locating the NCC. Bi-stable percepts, such as the Necker cube, may prove useful in examining the conscious mind's alternating wield of perception. They also address binocular rivalry as an example of this alternation. In addition, through neuroanatomical studies, Crick and Koch have claimed that areas such as V1 are not a part of the NCC. This claim was made based upon the fact that V1, in macaque monkeys, does not make any direct projections to the frontal cortex. Ned Block argues that, to make this argument, Crick and Koch have necessarily conflated two separate modes of consciousness. He makes the distinction between phenomenal and access consciousness, and calls their argument regarding the former unjustified, and that regarding the latter trivial. Just like the concept of memory, it is expected that consciousness will be elucidated with its own more complex vocabulary as research progresses.

It has been most interesting to me this semester to consider these questions in the light of perception. How exactly can a physical system with a particutular architecture give rise to feelings and qualia? This will surely be concertedly explored as new imaging and experimental paradigms are developed. It will continue to be a profound interest of mine.

Neural Basis of Consciousness
How Not to Find the Neural Correlate of Consciousness
Crick, F. and Koch, C. (1995),“Are we aware of neural activity in primary visual cortex?” Nature 375, 121-123, May 11
Hartmann, J.A. et.al. (1991), “Denial of visual perception,” Brain and Cognition 16, 29-40
Milner, A. D. & Goodale, M. A. (1995) The Visual Brain in Action. Oxford University Press: Oxford
Velmans M 1991 Is human information processing conscious? Behavioral Brain Science 14: 651-726