Neurophysiological indices of free recall memory biases in major depression: The impact of stimulus arousal and valence

This study examined differential impact of the valence and arousal characteristics of stimuli on memory biases and brain activity in major depressive disorder (MDD) and non-depressed control participants. P300 and slow wave (SW) components of the event-related brain potential (ERP) were recorded in 18 MDD and 18 control individuals during the encoding of positive and negative, high and low arousal words in a free recall task. Control participants demonstrated expected enhanced memory for positive stimuli that was accompanied by a corresponding increase in SW ERP components. These effects were not seen in the MDD participants. Rather, memory biases for negative information in MDD were only observed for low arousal words and were not reflected in ERP amplitudes. This study suggests that the inconsistency in the MDD memory bias literature may be related to the arousing nature of the stimuli incorporated in the study.