scholarly journals Adaptive Top–Down Suppression of Hippocampal Activity and the Purging of Intrusive Memories from Consciousness

2015 ◽  
Vol 27 (1) ◽  
pp. 96-111 ◽  
Author(s):  
Roland G. Benoit ◽  
Justin C. Hulbert ◽  
Ean Huddleston ◽  
Michael C. Anderson
Keyword(s):  
Effective Connectivity ◽  
Traumatic Experiences ◽  
Inhibitory Influence ◽  
Top Down ◽  
Intrusive Memories ◽  
Retrieval Processes ◽  
Hippocampal Activity ◽  
Dorsolateral Prefrontal ◽  
Intrusive Memory

When reminded of unwanted memories, people often attempt to suppress these experiences from awareness. Prior work indicates that control processes mediated by the dorsolateral prefrontal cortex (DLPFC) modulate hippocampal activity during such retrieval suppression. It remains unknown whether this modulation plays a role in purging an intrusive memory from consciousness. Here, we combined fMRI and effective connectivity analyses with phenomenological reports to scrutinize a role for adaptive top–down suppression of hippocampal retrieval processes in terminating mnemonic awareness of intrusive memories. Participants either suppressed or recalled memories of pictures depicting faces or places. After each trial, they reported their success at regulating awareness of the memory. DLPFC activation was greatest when unwanted memories intruded into consciousness and needed to be purged, and this increased engagement predicted superior control of intrusive memories over time. However, hippocampal activity was decreased during the suppression of place memories only. Importantly, the inhibitory influence of the DLPFC on the hippocampus was linked to the ensuing reduction in intrusions of the suppressed memories. Individuals who exhibited negative top–down coupling during early suppression attempts experienced fewer involuntary memory intrusions later on. Over repeated suppressions, the DLPFC–hippocampus connectivity grew less negative with the degree that they no longer had to purge unwanted memories from awareness. These findings support a role of DLPFC in countermanding the unfolding recollection of an unwanted memory via the suppression of hippocampal processing, a mechanism that may contribute to adaptation in the aftermath of traumatic experiences.

scholarly journals Selectively Interfering With Intrusive but Not Voluntary Memories of a Trauma Film: Accounting for the Role of Associative Memory

2021 ◽  
pp. 216770262199831
Author(s):  
Alex Lau-Zhu ◽  
Richard N. Henson ◽  
Emily A. Holmes
Keyword(s):  
Emotional Disorders ◽  
Traumatic Event ◽  
Emotional Memory ◽  
Control Procedure ◽  
Witness Testimony ◽  
Intrusive Memories ◽  
Therapeutic Benefits ◽  
Selective Interference ◽  
Intrusive Memory

Intrusive memories of a traumatic event can be reduced by a subsequent interference procedure, seemingly sparing voluntary memory for that event. This selective-interference effect has potential therapeutic benefits (e.g., for emotional disorders) and legal importance (e.g., for witness testimony). However, the measurements of intrusive memory and voluntary memory typically differ in the role of associations between a cue and the emotional memory “hotspots.” To test this, we asked participants to watch a traumatic film followed by either an interference procedure (reminder plus Tetris) or control procedure (reminder only). Measurement of intrusions (using a laboratory task) and voluntary memory (recognition for film stills) were crossed with the presence or absence of associative cues. The reminder-plus-Tetris group exhibited fewer intrusions despite comparable recognition memory, replicating the results of prior studies. Note that this selective interference did not appear to depend on associative cues. This involuntary versus voluntary memory dissociation for emotional material further supports separate-trace memory theories and has applied advantages.

scholarly journals Hypothalamic effective connectivity at rest is associated with body weight and energy homeostasis

2021 ◽  
Author(s):  
Katharina Voigt ◽  
Zane B Andrews ◽  
Ian H Harding ◽  
Adeel Razi ◽  
Antonio Verdejo-Garcia
Keyword(s):  
Information Flow ◽  
Weight Status ◽  
Energy Homeostasis ◽  
Effective Connectivity ◽  
Brain Networks ◽  
Substantia Nigra Pars Compacta ◽  
Central Component ◽  
Inhibitory Influence ◽  
Eating Behaviours ◽  
Top Down

Hunger and satiety states drive eating behaviours via changes in brain function. The hypothalamus is a central component of the brain networks that regulate food intake. Animal research parsed the roles of the lateral hypothalamus (LH) and the medial hypothalamus (MH) in hunger and satiety respectively. Here, we examined how hunger and satiety change information flow between human LH and MH brain networks, and how these interactions are influenced by body mass index. Forty participants (15 overweight/obese) underwent two resting-state functional MRI scans: after overnight fasting (fasted state) and following a standardised meal (sated state). The direction and valence (excitatory/inhibitory influence) of information flow between the MH and LH was modelled using spectral dynamic causal modelling. Our results revealed two core networks interacting across homeostatic state and weight status: subcortical bidirectional connections between the LH, MH and the substantia nigra pars compacta (prSN), and cortical top-down inhibition from frontoparietal and temporal areas. During fasting relative to satiety, we found higher inhibition between the LH and prSN, whereas the prSN received greater top-down inhibition from across the cortex. Individuals with higher BMI showed that these network dynamics occur irrespective of fasted or satiety states. Our findings reveal fasting affects brain dynamics over a distributed hypothalamic-midbrain-cortical network. This network is less sensitive to state-related fluctuations among people with obesity.

scholarly journals The Role of a Right Fronto-Parietal Network in Cognitive Control

2006 ◽  
Vol 20 (4) ◽  
pp. 286-296 ◽  
Author(s):  
C. Fassbender ◽  
C. Simoes-Franklin ◽  
K. Murphy ◽  
R. Hester ◽  
J. Meaney ◽  
...  
Keyword(s):  
Cognitive Control ◽  
Attentional Control ◽  
Control Process ◽  
Brain Regions ◽  
Top Down ◽  
Color Changes ◽  
Prepotent Response ◽  
Dorsolateral Prefrontal ◽  
The Right

Seemingly distinct cognitive tasks often activate similar anatomical networks. For example, the right fronto-parietal cortex is active across a wide variety of paradigms suggesting that these regions may subserve a general cognitive function. We utilized fMRI and a GO/NOGO task consisting of two conditions, one with intermittent unpredictive “cues-to-attend” and the other without any “cues-to-attend,” in order to investigate areas involved in inhibition of a prepotent response and top-down attentional control. Sixteen subjects (5 male, ages ranging from 20 to 30 years) responded to an alternating sequence of the letters X and Y and withheld responding when the alternating sequence was broken (e.g., when X followed an X). Cues were rare stimulus font-color changes, which were linked to a simple instruction to attend to the task at hand. We hypothesized that inhibitions and cues, despite requiring quite different responses from subjects, might engage similar top-down attentional control processes and would thus share a common network of anatomical substrates. Although inhibitions and cues activated a number of distinct brain regions, a similar network of right dorsolateral prefrontal and inferior parietal regions was active for both. These results suggest that this network, commonly activated for response inhibition, may subserve a more general cognitive control process involved in allocating top-down attentional resources.

Top-Down Processing and Visual Reorientation Illusions in a Virtual Reality Environment

2004 ◽  
Vol 63 (3) ◽  
pp. 143-149 ◽  
Author(s):  
Fred W. Mast ◽  
Charles M. Oman
Keyword(s):  
Virtual Reality ◽  
Visual Processing ◽  
Line Length ◽  
Perceptual Cues ◽  
Virtual Reality Environment ◽  
Top Down ◽  
Test Conditions ◽  
The Subject ◽  
Processing Mechanisms

The role of top-down processing on the horizontal-vertical line length illusion was examined by means of an ambiguous room with dual visual verticals. In one of the test conditions, the subjects were cued to one of the two verticals and were instructed to cognitively reassign the apparent vertical to the cued orientation. When they have mentally adjusted their perception, two lines in a plus sign configuration appeared and the subjects had to evaluate which line was longer. The results showed that the line length appeared longer when it was aligned with the direction of the vertical currently perceived by the subject. This study provides a demonstration that top-down processing influences lower level visual processing mechanisms. In another test condition, the subjects had all perceptual cues available and the influence was even stronger.

TESTING GOAL-DRIVEN CAPTURE BY THREAT

2019 ◽  
Author(s):  
Chris Robert Harrison Brown
Keyword(s):  
Experimental Evidence ◽  
Attentional Capture ◽  
Critical Role ◽  
Experimental Manipulation ◽  
Contingent Capture ◽  
Top Down ◽  
Affective Stimuli ◽  
Clinical Disorders ◽  
Positive Stimuli

Attention has long been characterised within prominent models as reflecting a competition between goal-driven and stimulus-driven processes. It remains unclear, however, how involuntary attentional capture by affective stimuli, such as threat-laden content, fits into such models. While such effects were traditionally held to reflect stimulus-driven processes, recent research has increasingly implicated a critical role of goal-driven processes. Here we test an alternative goal-driven account of involuntary attentional capture by threat, using an experimental manipulation of goal-driven attention. To this end we combined the classic ‘contingent capture’ and ‘emotion-induced blink’ (EIB) paradigms in an RSVP task with both positive or threatening target search goals. Across six experiments, positive and threat distractors were presented in peripheral, parafoveal, and central locations. Across all distractor locations, we found that involuntary attentional capture by irrelevant threatening distractors could be induced via the adoption of a search goal for a threatening category; adopting a goal for a positive category conversely led to capture only by positive stimuli. Our findings provide direct experimental evidence for a causal role of voluntary goals in involuntary capture by irrelevant threat stimuli, and hence demonstrate the plausibility of a top-down account of this phenomenon. We discuss the implications of these findings in relation to current cognitive models of attention and clinical disorders.

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