N1-P2 Evoked Response as a Measure for Short-Term Visual Memory

We investigate the relationship of N1-P2 evoked response (peak-to-peak amplitude and time interval) with short-term visual memory in humans. Visual evoked responses obtained from 20 subjects (10 nonamnesic alcoholics and 10 non-alcoholics) are extracted from channel P8 referenced to channel Cz during the presentation of modified delayed matching-to-sample visual task using Snodgrass and Vanderwart picture set. Our results indicate that N1P2 amplitudes are higher for non-matching (novel) stimuli as compared to matching stimuli for all the subjects. N1-P2 time interval is also shorter for the case of matching stimuli. This indicates that information processing is increased for the nonmatching stimuli as compared to matching stimuli. These results are quite consistent with a number of related studies and we conclude that N1-P2 is related to short-term visual memory involved during object recognition. The results also indicate that N1-P2 amplitude is higher for non-alcoholics as compared to alcoholics, which indicates that some form of memory impairment exist in alcoholics.