Necessity of occipital cortex for retrieving and re-experiencing negative memories

Boston College, Chestnut Hill MA

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Abstract

Project Abstract Distressful re-experiencing of negative memories is a common feature across a range of disparate psychiatric conditions, from post-traumatic stress disorder (PTSD) to obsessive-compulsive disorder. Prior work has shown that negative memories are associated with greater visual re-experiencing in healthy individuals, but extreme visual re-experiencing is symptomatic in these psychiatric conditions. Indeed, when re-experiencing processes go awry, such as in PTSD, the consequences for the individual and related societal costs can be devastating. The proposed examination of visual re-experiencing in healthy individuals is necessary before re- experiencing symptoms in psychological conditions can be fully understood. While the field of emotional memory has mostly focused on the contributions of the medial temporal lobe regions (e.g., amygdala) to emotionally enhanced memory, recent work?including my own?suggests a role for visual processing regions. I have consistently found correlational evidence linking enhanced engagement of the right lateral occipital cortex (rLOC) with the formation and retrieval of negative memories, compared to positive and neutral memories. Despite this correlational evidence, it is not known whether recruitment of visual processing regions is causally linked to retrieval, visual re-experiencing, and stabilization of negative memories. Therefore, the central hypothesis is that visual re-experiencing is enhanced for negative memories and is causally linked to memory-related computations carried out in the rLOC. In Aim 1, I will test the hypothesis that negative memories are associated with a greater sense of visual re-experiencing, compared to internal re-experiencing of thoughts or feelings at the time of encoding. In Aim 2, I will use repetitive transcranial magnetic stimulation (rTMS)?a non-invasive tool used to examine causal links between brain and behavior?to test the hypothesis that rLOC engagement is necessary for retrieval, visual re-experiencing, and stabilization of negative memories. In a within-subject design, participants in both Aims will study negative, positive, and neutral images. Participants will then be administered a recognition test and asked to make visual and internal re- experiencing ratings. For the purposes of Aim 2, the recognition test will be divided into two blocks, each immediately preceded by MRI image-guided inhibitory rTMS to the rLOC or vertex (counterbalanced across participants). A follow-up recognition test will assess whether inhibitory effects of rLOC on negative memories only affect memory during the active stimulation period, or if they persist beyond the active stimulation period, perhaps by affecting reconsolidation after a retrieval attempt. The proposed work will have an important positive impact on the field of emotional memory and the cognitive neuroscience more broadly (e.g., memory, emotion, decision making, prospection). The outcomes will provide a healthy comparison model for clinicians developing therapeutic approaches to alleviate emotional memory biases in psychopathology.