NEUROPHYSIOLOGIC CORRELATES OF IMPLICIT FACE MEMORY IN INTRACRANIAL VISUAL-EVOKED POTENTIALS

Visual evoked potentials were recorded in the amygdala, hippocampus, m id- and inferotemporal cortex, orbitofrontal cortex, and lateral front al cortex of seven epileptic patients while they were engaged in a dif ficult task requiring the discrimination between repeated and nonrepea ted faces. The explicit recognition of previously seen faces was at ch ance levels, as measured by the accuracy of push-button responses. Nev ertheless, all subjects showed clear-cut differential evoked responses to repeated versus nonrepeated faces, indicating implicit encoding of the distinction between the two types of stimuli. Differential respon ses mere more frequent in neocortical recording sites (especially in t he mid- and inferotemporal leads) than in limbic recording sites such as the amygdala and hippocampus. The authors conclude that implicit en coding processes are modulated by neocortical visual association areas of the temporal lobes.