The disunity of consciousness.

Consciousness is commonly considered to be a single entity, as expressed in the term "unity of consciousness", and neurobiologists are fond of believing that, sooner or later, they will be able to determine its neural correlate (rather than its neural correlates). Here I propose an alternative view, derived from compelling experimental and clinical studies of the primate visual cortex, which suggest that consciousness is not a single unity but consists instead of many components (the micro-consciousnesses) which are distributed in space and time. In this article, I propose that there are multiple consciousnesses which constitute a hierarchy (Zeki and Bartels, 1998, 1999), with what Kant (1996) called the 'synthetic, transcendental' unified consciousness (that of myself as the perceiving person) sitting at the apex. Here, I restrict myself to writing about visual consciousness and, within vision, mainly about the colour and the visual motion systems, about which we know relatively more. For if it can be shown that we are conscious of these two attributes at different times, because of spatially and temporally different mechanisms, then the statement that there is a single, unified consciousness cannot be true.