Theta event-related synchronization is a biomarker for a morbid effect of alcoholism on the brain that may partially resolve with extended abstinence

Abstract

Analyzing the induced (non-stimulus-phase-locked) EEG activity elicited by targets in a three-condition visual oddball task, Fein and colleagues have shown increased theta band event-related synchronization (ERS) in two different samples of long-term abstinent alcoholics (LTAA) compared with age- and gender-comparable controls. The theta ERS effect in alcoholics was also shown to be independent of, and opposite in direction to, the reduced amplitude evoked (stimulus-phase-locked) activity typically found in alcoholics and those at genetic risk of developing alcoholism. This study extends these findings by applying time-frequency analysis to target stimulus event-related EEG to compare evoked and induced theta activity in 43 LTAA and 72 nonalcoholic controls with a group of 31 alcoholics who just recently initiated abstinence from alcohol (between 6- and 15-week abstinent; referred to as short-term abstinent alcoholics, STAA). Results demonstrated that (1) evoked theta power was reduced to the same degree in STAA and LTAA compared with nonalcoholic control participants, while (2) induced theta activity, measured by theta ERS, was increased in both STAA and LTAA relative to controls, but was also increased in STAA relative to LTAA. The STAA and LTAA groups did not differ on measures of alcohol use severity or family history of alcohol problems. These results, coupled with previous findings that show a relationship between stronger theta ERS and increased memory load and attention allocation, suggest that increased theta ERS may be a biomarker for a detrimental effect of chronic alcohol abuse on the brain - a detriment that may recover, at least partially, with extended abstinence.

Keywords: Abstinent; EEG; alcoholism; biomarker; event-related synchronization; theta; time-frequency.

Figure 1

At top are the grand-averaged ERPs at electrode Pz for the target stimulus for NAC, LTAA, and STAA. Below are the grand-averaged evoked (stimulus-phase-locked) time-frequency representations (TFR), band-pass filtered in the theta band (3–8 Hz) to accentuate the relevant activity, at electrode Pz for the target stimulus for NAC, LTAA, and STAA, together with the topographic maps for the mean activity within the theta time-frequency region of interest (indicated by the dashed box on each TFR). The topographic maps are scaled differently so as to clearly indicate the spatial distribution of each.

Figure 2

Grand-averaged induced (non-stimulus-phase-locked) time-frequency representations (TFR), band-pass filtered in the theta band (3–8 Hz) to accentuate the relevant activity, at electrode FCz for the target stimulus for NAC, LTAA, and STAA. The poststimulus and prestimulus theta TFROIs are indicated by dashed boxes on the TFRs. Topographic maps for the mean activity within the poststimulus theta TFROI for NAC, LTAA, and STAA are shown.