In two ERP experiments, we examined whether active inhibition is involved in intentional forgetting. Both experiments consisted of a nondirected-forgetting (nDF) and a directed-forgetting (DF) block. Participants were sequentially presented with a prime, an R/F (remember/forget) cue, and a target. Participants made lexical decisions to both the primes and targets (Experiment 1) or only to the targets (Experiment 2). They were also instructed to remember or to forget the primes in response to the R/F cues in the DF block but to ignore these cues in the nDF block. The N400 semantic priming effect was observed when comparing the ERPs elicited by semantically unrelated and related targets in the DF block. In comparison to the nDF block, the N400 effect was greatly reduced for targets preceded by F cues in the DF block. These findings suggest that semantic processing is reduced by the instruction to forget and active inhibition is involved in intentional forgetting.
Background: Rumination, a tendency to focus on negative self-related thoughts, is a central symptom of depression. Studying the self-related aspect of such symptoms is challenging because of the need to distinguish self effects from the emotional content of task stimuli. This study employed an emotionally neutral self-related paradigm to investigate possible altered self-processing in depression and its link to rumination. Methods: People with major depressive disorder (n = 25) and controls (n = 25) underwent task-based electroencephalogram recording. We studied late event-related potentials, along with low-frequency oscillatory power. We compared electroencephalogram metrics between groups and correlated them with depressive symptoms and reported rumination. Results: Participants with major depressive disorder displayed a difference in late positive potentials across frontocentral electrodes between self-related and non-self-related conditions. We found no such difference in controls. The magnitude of this difference was positively correlated with depressive symptoms and reported rumination. Participants with major depressive disorder also had elevated theta oscillation power at central electrodes in self-related conditions, a finding that we did not see in controls. Limitations: Patients with major depressive disorder were medicated at the time of the study. The group studied was primarily female, so the observed effects may have been sex-specific. Conclusion: Rumination appears to be linked to altered self-related processing in depression, independ ent of stimuli-related emotional confounds. This connection between self-related processing and depression may point to a self disorder as a core component of depression.
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