The buzz of consciousness

“Its meaning we know so long as no one asks us to define it, but to give an accurate account of it is the most difficult of philosophic tasks.” – William James, 1890

These words remain true today: consciousness is both self-evident and enigmatic. In William James’ lucid phenomenological description,1 “the stream of thought” is “part of a personal consciousness,” “always changing” but “sensibly continuous,” dealing “with objects independent of itself” and displaying considerable selectivity. James’ prescient observations are embodied in a modern theory, in which consciousness depends on the activity of a distributed neural network that is dynamically reconfigured from instant to instant, through attention selecting one out of a vast number of possible states.2 In this theory, attention “binds” the activity of neurons in different brain regions into a unified state. One proposed mechanism for such binding is temporal synchrony of neuronal discharges, which leads to rhythmic firing every 15 to 30 milliseconds. Thus, a given state of the network reflecting a specific content of consciousness corresponds to a subset of active neurons transiently bound together by temporally synchronized firing. This idea was first formalized by von der Marlsburg3 as a solution to the more circumscribed problem of binding in the visual system. The problem arises …