Gamma band analysis of VEP to study the electrophysiological differences in alcoholics (original) (raw)

2002

Abstract

Introduction In this paper, we analyse Visual Evoked Potential (VEP) in the gamma band range of 30-50 Hz to study the electrophysiological differences between alcoholics and non-alcoholics. Gamma band spectrum is used specifically in the analysis because it has been shown to be closely related to higher brain functions like memory and object recognition [1]. However, the use of gamma band spectrum to analyse electrophysiological differences in alcoholics is novel. The VEP signals are extracted from 64 electrodes while the subjects are seeing 2 visual stimuli (presented with an interval in-between) from the Snodgrass and Vanderwart picture set. The experimental paradigm is designed to evoke visual short-term memory and object recognition abilities. Twenty subjects participated in the experimental study consisting of 10 alcoholics and 10 non-alcoholics. Forward and reverse Butterworth digital filter is used to extract VEP signals in gamma band spectral range. Parseval’s theorem is used obtain the equivalent gamma band spectral power. The results using t-Test analysis indicate that alcoholics give lower gamma band spectral power as compared to nonalcoholics in certain channels located in the central, occipital and parietal regions. This shows that some alterations to the brain processes that involve visual shortterm memory and object recognition are caused by longterm use of alcohol. The nature of these alterations is still traceable after a period of time, which is indicated by the fact that the studied alcoholics had been abstinent for a period of more than a month.

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