To the best of our knowledge, consciousness depends upon brains, and brains are biological organs. In a boxing match, a blow to the jaw often leads to a loss of consciousness, but the same impact to the torso does not. More specifically, scientists have long thought that human consciousness depends upon two large brain structures, the cortex and the thalamus. The daily cycle of waking, dreaming and sleep depends on distinctive global rhythm generators in the thalamus and cortex. (www.baars-gage.com, Chapter 8)
While deep brain nuclei control the daily sleep-waking cycle, the specific contents of conscious vision, like the sight of a coffee cup, are directly supported by known regions of the cortex and corresponding nuclei in the thalamus. Cortex and its satellites underlie speech and hearing, vision, hearing and touch, the ability to make decisions and to control our voluntary muscles.
In contrast, medical students have long learned that the two large lobes of the cerebellum, hanging from the rear of the cortex, can be damaged in humans without impairing consciousness significantly. Since the cerebellum has nearly the same numbers of neurons as cortex, the question therefore becomes: How it is that cortex supports conscious contents? Why not the cerebellum? (Figure 1).