If we could look through the skull into the brain of a consciously thinking person, and if the place of optimal excitability were luminous, then we should see playing over the cerebral surface, a bright spot with fantastic, waving borders constantly fluctuating in size and form, surrounded by a darkness more or less deep, covering the rest of the hemisphere.

Lectures on Conditioned Reflexes...: Conditioned reflexes and psychiatry... translated and edited by W. H. Gantt (ed. 1941)