Sunday, July 09, 2006

Reclaiming Homunculus in a non-trivial way.

On the first day of a neurosciences course at universities, the students are told that there is no specific "seat for consciousness" in the brain. The modern description of the link between brain activities and subjective experience starts from the assumption that there is no "little person" in the brain monitoring the neural activities in various areas of the brain. The "exorcision" of the Homunculus was a necessary and essential step in the advancement of cognitive neuroscience, and the concept of the "neural correlate" is the de facto central dogma in neurophenomenology today. The practical beauty of the neural correlate concept lies in the fact that it apparently does not need any central monitoring area. Under the neural correlate paradigm, appropriate neural activity patterns give rise to corresponding elements of subjective experience without any need for a monitoring region, a "little person" in the brain.
However, it could be argued with considerable logical rigor that in order to come to a breakthrough in the hard problems of qualia and subjectivity, one may need to "reclaim" homunculus. Experimental data ranging from binocular rivalry to body image consistently show that when there is a perceived element of phenomenal experience, that element is always incurred in the context of a "subjectivity" structure sustained by the brain's intentional system centered around the prefrontal region. The neural correlate concept, as it stands, is not self-sufficient and need to be complemented by a neural mechanism of subjectivity. We need to "reclaim" the homunculus, not in the old fashioned way but in a non-trivial, systems-oriented version.
The essential difficulty in coming to a modern version of the homunculus becomes apparent when one considers the massive parallelness and phenomenal heterogeneity (as is evident in, e.g., "change blindness") of visual awareness. It is not a trivial task to devise a model of the neural processes involved in invoking the massively parallel visual qualia as perceived by a single subjective agent in an integrated fashion.
In order to reconstruct homculus in a non-trivial way, we need a generalized "metacognitive" model in which not only the typical metacognition (as in the case of Wisconsin card sorting tests or uncertainty monitoring) but also the general conscious perception is treated in a way such that the non-trivial homunculus is invoked in every essential aspect of the cognitive process.

(This entry is a revised and extended version of the talk presented by Ken Mogi at the Tucson 2004 conference under the title "Reclaiming Homunculus".)