The impact of torture on interpersonal threat and reward neurocircuitry

Torture Exposure Modulates Cognitive Control and Attention Neural Network Connectivity During a Go/Nogo Task

BACKGROUND

Torture trauma is characterised by intentional uncontrollable acts, but the long-term effects of torture exposure on cognitive control brain mechanisms are unknown.

METHODS

A final sample of 33 torture survivors (TS) and 44 non-torture survivors (NTS), all with a refugee background, completed a Go/NoGo response inhibition task during fMRI scanning. Data-driven independent components analysis identified active networks across the task, and within Go, NoGo and error of commission trials. Groups were compared on within/between network connectivity, controlling for demographic and psychological symptom covariates. Secondary analyses investigated whether network connectivity moderated the associations between torture exposure and severity on fear (e.g. re-experiencing) and dysphoria (e.g. anhedonia) posttraumatic stress disorder (PTSD) symptoms.

RESULTS

The TS group exhibited decreased connectivity (compared to NTS controls) within the posterior default mode network (specifically the left precuneus) and auditory-motor network (specifically right superior temporal gyrus STG), and reduced connectivity between the dorsomedial frontal network (dmFN) and dorsal attention network (dAN) across the Go/NoGo task. The TS group also showed comparatively more negative ventral attention network connectivity during NoGo (i.e. inhibition) trials. No behavioral effects were observed. Secondary analyses revealed that association between torture exposure and elevated PTSD dysphoria (not fear) symptoms was moderated by reduced connectivity in the right STG and between the dmFN-dAN.

CONCLUSIONS

Response inhibition, attention and motor networks appear less connected in torture survivors, which may be specifically linked to PTSD dysphoria symptom profiles. Findings suggest that targeting cognitive control processes may hold promise for alleviating post-traumatic symptoms amongst survivors of torture.

Adverse Life Experiences and Brain Function: A Meta-Analysis of Functional Magnetic Resonance Imaging Findings

Importance

Adverse life experiences have been proposed to contribute to diverse mental health problems through an association with corticolimbic functioning. Despite compelling evidence from animal models, findings from studies in humans have been mixed; activation likelihood estimation (ALE) meta-analyses have failed to identify a consistent association of adverse events with brain function.

Objective

To investigate the association of adversity exposure with altered brain reactivity using multilevel kernel density analyses (MKDA), a meta-analytic approach considered more robust than ALE to small sample sizes and methodological differences between studies.

Data Sources

Searches were conducted using PsycInfo, Medline, EMBASE, and Web of Science from inception through May 4, 2022. The following search term combinations were used for each database: trauma, posttraumatic stress disorder (PTSD), abuse, maltreatment, poverty, adversity, or stress; and functional magnetic resonance imaging (fMRI) or neuroimaging; and emotion, emotion regulation, memory, memory processing, inhibitory control, executive functioning, reward, or reward processing.

Study Selection

Task-based fMRI studies within 4 domains (emotion processing, memory processing, inhibitory control, and reward processing) that included a measure of adverse life experiences and whole-brain coordinate results reported in Talairach or Montreal Neurological Institute space were included. Conference abstracts, books, reviews, meta-analyses, opinions, animal studies, articles not in English, and studies with fewer than 5 participants were excluded.

Data Extraction and Synthesis

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses reporting guideline, 2 independent reviewers assessed abstracts and full-text articles for entry criteria. A third reviewer resolved conflicts and errors in data extraction. Data were pooled using a random-effects model and data analysis occurred from August to November 2022.

Main Outcomes and Measures

Peak activation x-axis (left-right), y-axis (posterior-anterior), and z-axis (inferior-superior) coordinates were extracted from all studies and submitted to MKDA meta-analyses.

Results

A total of 83 fMRI studies were included in the meta-analysis, yielding a combined sample of 5242 participants and 801 coordinates. Adversity exposure was associated with higher amygdala reactivity (familywise error rate corrected at P < .001; x-axis = 22; y-axis = -4; z-axis = -17) and lower prefrontal cortical reactivity (familywise error rate corrected at P < .001; x-axis = 10; y-axis = 60; z-axis = 10) across a range of task domains. These altered responses were only observed in studies that used adult participants and were clearest among those who had been exposed to severe threat and trauma.

Conclusions and Relevance

In this meta-analysis of fMRI studies of adversity exposure and brain function, prior adversity exposure was associated with altered adult brain reactivity to diverse challenges. These results might better identify how adversity diminishes the ability to cope with later stressors and produces enduring susceptibility to mental health problems.

Torture exposure and the functional brain: investigating disruptions to intrinsic network connectivity using resting state fMRI

Torture has profound psychological and physiological consequences for survivors. While some brain structures and functions appear altered in torture survivors, it is unclear how torture exposure influences functional connectivity within and between core intrinsic brain networks. In this study, 37 torture survivors (TS) and 62 non-torture survivors (NTS) participated in a resting-state fMRI scan. Data-driven independent components analysis identified active intrinsic networks. Group differences in functional connectivity in the default mode network (DMN), salience network (SN) and central executive network (CEN) of the triple network model, as well any prefrontal network, were examined while controlling for PTSD symptoms and exposure to other potentially traumatic events. The analysis identified 25 networks; eight comprised our networks of interest. Within-network group differences were observed in the left CEN (lCEN), where the TS group showed less spectral power in the low-frequency band. Differential internetwork dynamic connectivity patterns were observed, where the TS group showed stronger positive coupling between the lCEN and anterior dorsomedial and ventromedial DMN, and stronger negative coupling between a lateral frontal network and the lCEN and anterior dorsomedial DMN (when contrasted with the NTS group). Group differences were not attributed to torture severity or dissociative symptoms. Torture survivors showed disrupted dynamic functional connectivity between a laterally-aligned lCEN that serves top-down control functions over external processes and the midline DMN that underpins internal self-referential processes, which may be an adaptive response to mitigate the worst effects of the torture experience. This study provides a critical step in mapping the neural signature of torture exposure to guide treatment development and selection.