Topography, power, and current source density of theta oscillations during reward processing as markers for alcohol dependence

Abstract

Recent studies have linked alcoholism with a dysfunctional neural reward system. Although several electrophysiological studies have explored reward processing in healthy individuals, such studies in alcohol dependent individuals are quite rare. The present study examines theta oscillations during reward processing in abstinent alcoholics. The electroencephalogram (EEG) was recorded in 38 abstinent alcoholics and 38 healthy controls as they performed a single outcome gambling task which involved outcomes of either loss or gain of an amount (10¢ or 50¢) that was bet. Event-related theta band (3.0–7.0 Hz) power following each outcome stimulus was computed using the S-transform method. Theta power at the time window of the outcome-related negativity (ORN) and positivity (ORP) (200–500 ms) was compared across groups and outcome conditions. Additionally, behavioral data of impulsivity and task performance were analyzed. The alcoholic group showed significantly decreased theta power during reward processing compared to controls. Current Source Density (CSD) maps of alcoholics revealed weaker and diffuse source activity for all conditions and weaker bilateral prefrontal sources during the Loss 50 condition as compared to controls who manifested stronger and focused midline sources. Further, alcoholics exhibited increased impulsivity and risk-taking on the behavioral measures. A strong association between reduced anterior theta power and impulsive task-performance was observed. It is suggested that decreased power and weaker and diffuse CSD in alcoholics may be due to dysfunctional neural reward circuitry. The relationship among alcoholism, theta oscillations, reward processing and impulsivity could offer clues to understand brain circuitries that mediate reward processing and inhibitory control.

Principal components analysis of reward prediction errors in a reinforcement learning task

“…Separation into theta and delta frequency bands revealed greater power for -RPEs in theta, and greater power for +RPEs in delta, supporting results of a number of recent studies (Bernat et al, 2015;Cavanagh, Frank, Klein, & Allen, 2010;Foti et al, 2014;Kamarajan et al, 2012;Marco-Pallares et al, 2008;Mas-Herrero & Marco-Pallarés, 2014).…”

Understanding alcohol use disorders with neuroelectrophysiology

“…In a recent study on reward processing in alcoholics during a gambling task, event-related theta band (3.0–7.0 Hz) oscillations were evaluated during the loss/gain feedback (Kamarajan et al, 2012). The alcoholic group showed significantly decreased theta power during reward processing compared to controls, particularly during the evaluation of loss.…”

A KCNJ6 gene polymorphism modulates theta oscillations during reward processing

“…The participants select a bet of either 50¢ or 10¢, and receive feedback of either loss or gain for the selected amount (outcome stimulus, OS). The task details have been described in our previous publications (Kamarajan et al, 2008; Kamarajan et al, 2012; Kamarajan et al, 2015a; Kamarajan et al, 2015b). The inter-stimulus interval between a CS and OS, and between an OS and the next CS is 1500 ms.…”

“…Specifically, ERO theta activity underlying feedback/outcome processing of monetary loss and gain (Luu et al, 2003; Gehring and Willoughby, 2004; Luu et al, 2004; Cohen et al, 2007; Kamarajan et al, 2008; Crowley et al, 2014) has been reported to be a highly useful measure to characterize reward circuitry dysfunction in psychiatric conditions (Oberg et al, 2011; Padrao et al, 2013; Andreou et al, 2015), including alcoholism (Kamarajan et al, 2012; Kamarajan et al, 2015a). …”

“…ERO theta power during a monetary gambling task has been reported to be reduced while processing monetary loss and gain in both alcoholics and their high risk offspring (Kamarajan et al, 2012; Kamarajan et al, 2015a), and the findings were interpreted as reward processing deficits in these groups. There is evidence to show that neural oscillations during reward processing underlie brain reward regions and/or circuits.…”