The brain's information processing power is limited by its energy supply but the allocation of cortical energy use between conscious and unconscious information processing is unknown. We calculate, from electrophysiological data in primates, that conscious perception reflects surprisingly small local alterations in mean cortical neuronal firing rate and energy consumption: perceiving visual stimulus movement, altered tactile vibration frequency, or tone stream separation, changes local cortical energy use by less than 6%. Our estimations of energy use suggest that a “design strategy”, of encoding signals using separate neurons that increase and decrease their firing rate, serves to minimise changes of energy use in the cortical areas mediating perception and may result in stimulus perception failing to be detected by BOLD functional imaging.
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