Academic journal article Cognitive, Affective and Behavioral Neuroscience

The Neural Correlates of Attempting to Suppress Negative versus Neutral Memories

Academic journal article Cognitive, Affective and Behavioral Neuroscience

The Neural Correlates of Attempting to Suppress Negative versus Neutral Memories

Article excerpt

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.

Anecdotal reports and empirical evidence have suggested that emotion enhances the subjective sense of remembering and, to a lesser degree, the accuracy of memory (Phelps & Sharot, 2008). From an evolutionary perspective, this is beneficial. Enhancement may lead to increased survival via quicker and more accurate responses to previously encountered stimuli that elicit emotional responses representing significance. However, as can be seen in such disorders as posttraumatic stress disorder (PTSD), the enhancement and persistence of memory for highly arousing and negative traumatic events can lead to devastating issues long after the event itself occurred (American Psychiatric Association, 2000). One way in which people cope with unwanted memories is by attempting to suppress them. Suppression of a memory is a construct that can be separated from physical avoidance of memory cues. It has been suggested that physical avoidance of memory cues may lead to a reinstatement of negative memories when a cue becomes unavoidable at a later time but that suppression of cued memories may allow for regulatory processes to occur, decreasing this reinstatement (Anderson, 2001).

There is some evidence suggesting that attempting to suppress recall may lead to poor emotional, behavioral, and cognitive outcomes (Dalgleish, Hauer, & Kuyken, 2008; Ehlers & Clark, 2000). Successful treatment of patients with traumatic memories has often involved the use of strategies that bring the memory into awareness in the absence of the negative emotional reaction (Harvey, Bryant, & Tarrier, 2003). These interventions generally have not involved suppression. It has been argued that the therapeutic effects of evoking the experience of emotional memories may depend on a reappraisal of the prior experience (Littrell, 1998). Thought suppression research has demonstrated that some of the negative consequences of suppression are related to psychopathologies (Purdon, 1999). Naturalistic studies of suppression after traumatic events have shown that suppression is positively correlated with a greater degree of reexperience and posttraumatic stress (Joseph et al., 1996; Mayou, Ehlers, & Bryant, 2002). Positive relationships between greater suppression of unwanted thoughts and greater nonsuicidal self-injury, suicidal ideation, and suicide attempts have been demonstrated (Najmi, Wegner, & Nock, 2007). …

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