ELECTROPHYSIOLOGIC DIFFERENCES TO ALCOHOL CHALLENGE IN INDIVIDUALS POLYMORPHIC AT ADH1B LOCI

Background The ADH Class 1 is the major group for metabolizing alcohol in humans. Subunits which constitute class 1 ADH are encoded by the three genes ADH1A, ADH1B, and ADH1C, giving rise to A, B, and C subunits. Genetic polymorphisms, occur at ADH1B to give rise to ADH1B1, ADH1B2, and ADH1B3 subunits. Concerning the ADH1B gene, individuals with the ADH1B3 genotype appear to be more resistant to the stimulating effects of alcohol, possibly due to a faster-metabolizing capacity of this variant compared to the wild-type (ADH1B1). The purpose of this study was to examine the effect of ADH1B polymorphisms on electroencephalography, using the alcohol clamp technique. We hypothesize that individuals heterozygous for the ADH1B3 allele will have lower alpha power in frontoparietal electrodes, suggesting less relaxation effect during alcohol ingestion compared to those homozygous for ADH1B1. Methods A pilot sample of individuals (N=28) genotyped at the ADH1B locus received continuous EEG recording during infusion, using the alcohol clamp technique. The collected EEG data was analyzed using EEGLAB, an open source electrophysiological data analysis software application. The data was preprocessed using FASTER, an EEGLAB plugin for Automated EEG artifact Rejection. The FASTER process applies independent component analysis and statistical thresholds for artifact rejection. The accepted EEG epochs were then submitted to the pwelch FFT implementation using the inbuilt functions of EEGLAB, which computed the power of the EEG in 0.24 Hz steps over a total range of 1.5 – 40 Hz. The power spectra were averaged over epochs and averaged amplitude peaks extracted. The estimates of power within the delta (1.5–3.2 Hz), theta (3.8– 7.02 Hz), alpha (7.8–12.5 Hz), and slow (13.2–18.75 Hz) and fast (19.5–39.8 Hz) beta frequency bands were computed as the area under the PSD curve. Results Subjects with ADH1B1/1 have increased alpha power in CZ, FZ and PZ leads during baseline (i.e. pre-alcohol exposure) eye-closed resting EEG, with the greatest difference (between ADH1B1/1 and ADH1B1/3 observed in the PZ leads (P Discussion Based on rich evidence from neurophysiological studies, increased alpha power is indicative of hypoarousal; therefore, our data subjects more evidence for cortical hypoarousal in anticipation of alcohol challenge among individuals with ADH1B1/1 polymorphism.