Neural Mechanisms Underlying Memory Control

We have all had moments in which an object or event reminds us of an experience that we would prefer not think about. When this happens, we often attempt to stop retrieval and exclude the unpleasant reminding from awareness. Such efforts at memory control are an unfortunately ubiquitous experience in the aftermath of trauma. This project seeks to understand the cognitive and neural mechanisms that enable people to control unwanted memories. The basic research will develop a theoretical framework for understanding how people control intrusive remindings by facilitating a deeper understanding of how attention interacts with long-term memory. A core hypothesis of this framework is that people engage mechanisms similar to those involved in suppressing reflexive actions to suppress memory retrieval, reducing activity in brain structures involved in memory, reducing a memory’s intrusiveness. Basic research specifying the cognitive and neurobiological mechanisms of memory control has the promise to inform theories of clinical syndromes characterized by disordered thought control such as PTSD (intrusive flashbacks), depression (unwanted ruminations), ADHD (distractability), obsessive compulsive disorder (obsessive thoughts) and addiction (craving related thoughts). In so doing, the current work could have a substantial positive impact on our ability to provide treatment to those suffering from such disorders.

This project seeks to understand the cognitive and neural mechanisms that enable people to control unwanted memories. Recent work by Anderson has found that when people confront a reminder to an experience that they would prefer not to think about, they engage executive control mechanisms often recruited to override prepotent motor responses to suppress retrieval. This work has led to a theoretical perspective in which memory control is accomplished by an attention system that interacts with memory and that is governed by principles and components isomorphic to those involved in perceptual orienting of attention. A key process is attentional inhibition, which is triggered by conflict between the goal-directed focus of attention and the focus demanded by reflexive orienting to abrupt onsets in mnemonic space. Attentional inhibition is conceptualized as a flexible component of task set that can be recruited when conflict is expected or present, to override reflexive memorial orienting. The current project aims to evaluate key hypotheses, including (a) the hippocampal modulation hypothesis, according to which memory control is affected by down-regulating mnemonic activity in the hippocampus, (b) the mnemonic attention hypothesis, in which memory intrusions constitute cases of mnemonic reflexive orienting that build on the same neural mechanisms engaged to reflexively orient attention to events in the perceptual world, (c) the response override hypothesis, in which mnemonic control is accomplished by brain mechanisms involved in overriding prepotent motor actions, and (d) the motivated forgetting hypothesis, in which memory control mechanisms lead to selective forgetting of unwanted events. The approach to this question will combine traditional cognitive methods, developed by Anderson, a new approach to measuring intrusions, as well as fMRI and EEG. If correct, this view stands to forge a highly specific connection between research on attention and long-term memory that will move beyond the simple observation that attention can be directed to memory to the nature of mnemonic attention system itself. This work will specify a rich framework in which to understand how people control unwanted memories of the past. Such insights are not merely of theoretical significance, but of potentially profound practical importance in understanding and ameliorating the conditions of those suffering from intrusive memories.