Obsessive-compulsive symptoms predict increased fronto-parahippocampal synchronisation during thought suppression.

Background: Thought suppression is suggested as a causal factor in obsessive-compulsive disorder (OCD), as it can lead to a paradoxical increase in intrusive thoughts. However, the neural mechanisms through which obsessive-compulsive symptoms (OCS) influence thought suppression, particularly in the context of attentional bias toward negatively valenced stimuli, remain unclear. We hypothesized that OCS would predict increased recruitment of frontal inhibitory neurocircuitry during the suppression of negative words and that this would be mediated by an attentional bias toward these stimuli. Methods: EEG was recorded from 48 non-clinical participants tasked with directed forgetting of negative and neutral words. We examined the influence of OCS on neural correlates of thought suppression, specifically fronto-parahippocampal beta-1 (13-18 Hz) synchronisation and alpha (8-12 Hz) activity in the parahippocampal cortex. The mediating role of attentional bias, measured via the late positive potential (LPP) following word was assessed using a mediated moderation model.Results: OCS predicted enhanced fronto-parahippocampal beta-1 synchronisation when instructed to forget negative words. This effect was mediated by attentional bias to negative stimuli, but only in individuals with higher levels of OCS. Conclusions: Individuals with higher OCS exhibit compensatory engagement of frontal inhibitory mechanisms when attempting to suppress negative emotional stimuli. This compensatory activity is influenced by both attentional bias to negative stimuli and the severity of OCS, highlighting a neural mechanism that may contribute to the persistence of intrusive thoughts in OCD.