The neural correlates of attempting to suppress negative versus neutral memories.

We performed an event-related fMRI study comparing attempts at suppressing recall of negative versus neutral memories. The hippocampus is crucial for successful explicit recall. Hippocampal activation has been shown to decrease during the suppression of previously learned neutral words. However, different effects may occur in the case of emotional memories. Participants first learned 40 word pairs consisting of a cue and either a neutral or a negative target. During fMRI scanning, the participants were shown the cues and were instructed to recall the targets or to suppress the targets, using attentional distraction. Similar right-lateralized frontoparietal regions were activated more during suppression than during recall, regardless of emotion. However, we show for the first time that lowered hippocampal activation occurs during the suppression of neutral, but not negative, words. Coinciding with this sustained hippocampal activation, the amygdala, insula, anterior cingulate, and fusiform gyrus showed greater activation during the suppression of negative memories than during suppression of neutral memories. Thus, during attempts to suppress negative memories, regions involved in the emotional and sensory aspects of memory reactivate, along with regions indexing conscious recall. Revealing the neural correlates and mechanisms of the suppression of negative memories has relevance for disorders such as posttraumatic stress disorder, in which traumatic memories often intrude and are associated with avoidance. Supplemental materials for this article may be downloaded from http://cabn.psychonomic-journals.org/content/supplemental.