Memory Control: A Fundamental Mechanism of Emotion Regulation Haakon G. Engen, Michael C. Anderson  Trends in Cognitive Sciences  Volume 22, Issue 11, Pages 982-995 (November 2018) DOI: 10.1016/j.tics.2018.07.015 Copyright © 2018 Elsevier Ltd Terms and Conditions

Figure 1 Neurobehavioral Markers of Affect Suppression Following Retrieval Suppression. Summary of results from [26] (adapted with permission). This study showed that DS both reduced the intrusiveness of affective images and had a lasting impact on affective reactions to them, such that subjective evaluations of suppressed stimuli were less negative. This affect-suppression effect resembles extinction learning [105], where affective responses to a conditioned threat-signaling stimulus are downregulated by repeated experiences that it no longer signals threat. This similarity also extends to the neural domain, and data suggest that direct suppression (DS) may engage prefrontal circuits to increase activity in inhibitory GABAergic interneurons within the MTL [58,60], whereas extinction learning occurs via prefrontally mediated engagement of GABAergic inhibitory circuits within the amygdala [105,106]. This suggests that the affective consequences of suppression could also rely on similar downregulation of the amygdala, a notion supported by analyses [23] showing that DS was associated with upregulation of prefrontal circuits and downregulation of the amygdala when aversive images intruded into awareness and needed to be purged (A). Importantly, the strength of this downregulation was associated with larger affect-suppression effects and fewer involuntary intrusions, indicating that that these neural effects were key to successful mnemonic and affective control (B), with effective connectivity analyses demonstrating that suppression effects were driven by the right MFG, which effected parallel suppression of the amygdala, the hippocampus, and the parahippocampus (C). It is unknown how the MFG achieves these suppression effects because MFG is not directly connected to either the amygdala or the hippocampus. However, it is connected to several regions that are thought to implement amygdala regulation, including the ventrolateral prefrontal cortex (vlPFC) [66–68,107], and dorsal [107,108] anterior cingulate [105,107–109]. These regions are also consistently engaged in DS (panel A; also Figure 2A and [59]), suggesting that they might be intermediate elements of a top-down regulatory pathway. Abbreviations: Amg, amygdala; BSR, bootstrapped standard ratio; Hip, hippocampus; MFG, mid-frontal gyrus; MTL, medial temporal lobe; NT, no-think; T, think. Trends in Cognitive Sciences 2018 22, 982-995DOI: (10.1016/j.tics.2018.07.015) Copyright © 2018 Elsevier Ltd Terms and Conditions

Figure 2 Neural Networks Underlying Memory Control (MC) and Reappraisal. Networks for (A) direct suppression, adapted from [59]; (B) thought substitution, adapted from [25]; and (C) reappraisal, reproduced, with permission, from [71,72]. Reappraisal areas are color-coded according to overlap with MC circuits. Blue outline, retrieval suppression; green outline, thought substitution; black outline, both. Abbreviations: AI, anterior insula; ANG, angular gyrus; dACC, dorsal anterior cingulate cortex; IFG, inferior frontal gyrus; IPL, inferior parietal lobule; MFG, mid-frontal gyrus; PCC, posterior cingulate cortex; SMA, supplementary motor area; TPJ, temporoparietal junction. Trends in Cognitive Sciences 2018 22, 982-995DOI: (10.1016/j.tics.2018.07.015) Copyright © 2018 Elsevier Ltd Terms and Conditions