The role of inhibitory control in forgetting unwanted memories: A consideration of three methods

When confronted with reminders to things that we would prefer not to think about, we often attempt to put the unwanted memories out of awareness. Here, I argue that the ability to control memory is a special case of a broad class of situations thought to require executive control: response override. In such situations, one must stop a strong habitual response to a stimulus due to situational demands, a function thought to be accomplished by inhibitory processes that suppress the response, enabling more flexible, context-sensitive control over behavior. Recent behavioral studies show that inhibitory mechanisms that control overt behavior are also targeted at declarative memories to control retrieval. Recent neuroimaging findings (Anderson et al., 2004) further establish that controlling awareness of unwanted memories is associated with increased dorsolateral prefrontal cortex activation, reduced hippocampal activation, and impaired retention of the unwanted trace and that the magnitude of activation in prefrontal cortex predicts memory suppression. These findings indicate that cognitive and neural systems that support our ability to override prepotent responses can be recruited to override declarative memory retrieval, and that this cognitive act leads to memory failure. The relation between these findings and those obtained with the directed forgetting procedure is also discussed.