Scopolamine impairs memory performance and reduces frontal but not parietal visual P3 amplitude

It has been suggested that the P3 event-related potential (ERP) may mark th e operation of certain working or long-term memory processes. It has also b een reported that cholinergic blockade by scopolamine induces significant m emory impairment and is associated with an increased latency, as well as am plitude reduction or abolition of the auditory pi, thus supporting hypothes ised links between P3 and long-term memory function. An intriguing anomaly is that, while visual P3 latency is also increased by scopolamine, amplitud e is not changed. The aim of this study was to make a more detailed assessm ent of the effects of scopolamine on the visual P3 at a drug dose known to induce memory impairment. After drug administration, memory performance was significantly impaired and visual P3 latency was significantly increased, There was little evidence of parietal P3 amplitude reduction, but frontal P 3 amplitude was significantly reduced in both target and non-target conditi ons. These findings, when considered in the light of a more recent study of the effects of scopolamine on auditory P3, suggest that cholinergic blocka de produces a common effect in both visual and auditory modalities of signi ficant frontal P3 amplitude reduction, but no significant parietal P3 ampli tude reduction. These results are consistent with the view that there are m odality-independent generators of the parietal and frontal P3. The finding of drug-induced memory impairment and modulations of frontal ERP deflection s is also consistent with recent evidence of a significant role for regions of the frontal lobe in encoding and retrieval of long-term memories. (C) 2 000 Elsevier Science B.V. All rights reserved.