AUDITORY AND VISUAL SENSORY REPRESENTATIONS IN HUMAN PREFRONTAL CORTEX AS REVEALED BY STIMULUS-EVOKED SPIKE-WAVE COMPLEXES

Multimodal sensory properties of the prefrontal cortex have been exten sively studied in monkeys, while little is known of such functions in humans. We report electrophysiological evidence for auditory and visua l representations in the dorsolateral prefrontal cortex, as inferred f rom intracerebral 'depth' recordings of focal, sensory-evoked spike-wa ve complexes (SWC) in an epileptic patient. In addition to clinical mo nitoring, the patient participated in behavioural evoked potential stu dies involving auditory and visual discrimination tasks. Inspection of evoked potential recordings from different medial-to-lateral prefront al sites revealed overlapping, but non-identical topographies of evoke d SWC for the two sensory modalities. The maximal activity of sensory- evoked SWC was located 7 mm more medially for visual than for auditory stimuli, and occurred later for visual presentations (mean = 117 ms f ollowing stimulus onset) than for auditory ones (mean = 87 ms). Effect s of sensory habituation were seen. Evoked SWC were less likely to occ ur following repeated presentations of an unchanging tone than when to nes alternated in pitch, or when a tone followed an omission in stimul us presentation. Visual hemifield effects were found, with greater pre frontal responsiveness to presentations in the contralateral visual he mifield. These results are consistent with electrophysiological findin gs in animals indicating overlapping auditory and visual representatio ns in the dorsolateral prefrontal cortex.