The Behavior and Electrophysiology of Directed Forgetting in the Auditory Domain
There are many instances in life when a person wants or needs to forget a memory. These unwanted memories can range from something that is simply now irrelevant such as an outdated fact, to something as serious as a traumatic experience. In extreme cases such as post-traumatic stress disorder, the benefit of forgetting becomes obvious. As such, it is important that we understand not only how our brain is able to remember, but also how it is able to forget. Unlike the traditional view of incidental forgetting, recent studies have shown that forgetting can be a strategic and active process. However, the mechanisms by which we can intentionally suppress our memories are not fully understood. Moreover, most of the directed forgetting research has focused on suppressing visual memories. A more complete understanding of the way we can exert inhibitory control over our memories should include all sensory modalities. To address this issue, we examined whether similar electrophysiological findings, as reported in visual electroencephalography (EEG) studies of directed forgetting, would be observed in the auditory domain. Additionally, the role of the prefrontal cortex in this higher-order process was investigated. Here, we utilized the Think/No-Think paradigm to examine the neural correlates of the cognitive control of memory in three studies. First, we compared findings from healthy young adults in two tasks that varied in the number of to-be-remembered and to-be-forgotten repetitions, and found that behavioral and electrophysiological evidence points to similar effects using auditory stimuli, but that it may be more difficult to achieve than the inhibition of visual memories. Second, we extended those findings to older adults, and found that they too showed behavioral and EEG evidence of successful suppression of unwanted auditory memories. Third, we determined that prefrontal cortex plays a causal role in the ability to actively inhibit auditory memories by examining the behavioral and EEG effects of unilateral frontal lesions in a patient cohort. The behavioral evidence for the inhibition of auditory memory and the corresponding electrophysiology is a step toward a more complete picture of how we intentionally suppress unwanted memories.