Individuals with depressive tendencies experience difficulty in forgetting negative material: two mechanisms revealed by ERP data in the directed forgetting paradigm

Although previous studies have shown that individuals with depressive tendencies have deficits in forgetting negative material, the detailed underlying neural mechanisms have not been elucidated. This study examined the intentional forgetting of negative and neutral material in individuals with depressive tendencies in two phases. In the study phase, the participants performed a directed forgetting task, where a total of 320 words were presented to them, each followed by an instructive cue to forget or remember the previously presented word. Subsequently, in the memory recognition test phase, the participants completed the old or new discrimination task. The results indicated that individuals with depressive tendencies had difficulties suppressing the memory encoding of negative words, while the suppression of memory encoding of neutral words was relatively intact. Moreover, individuals with depressive tendencies displayed enhanced word-evoked P2 and late positive potential for negative items, as well as enhanced cue-evoked P1 and N2 for the negative items that were required to be forgotten, as compared to individuals without depressive tendencies. Based on these results, we propose two mechanisms that may contribute to the failure of forgetting negative material in mild depression: (1) inefficient memory suppression and early selective attention, and (2) excessive preliminary processing.