Demers, L. et al. (2017). Separable effects of childhood maltreatment and adult adaptive functioning on amygdala connectivity during emotional processing. Society of Biological Psychiatry, 3, 116-124.
This review was undertaken by Drs. Duerden (Neurologist & Senior Research Associate, Sick Children’s Hospital) and Fallon (Associate Professor, Factor-Inwentash Faculty of Social Work, University of Toronto). The collaboration for the review was important to address the medical and social science used by the authors in order to understand the neurological impact of childhood maltreatment in adults.
There is substantial evidence that childhood maltreatment can result in a heightened physiological response of a particular brain region involved in emotion and fear known as the amygdala. This article used a psychophysiological-interaction model, whereby scores obtained on tasks related to adult adaptive functioning and incidence of maltreatment were assessed relative to functional brain connectivity in maltreated and non-maltreated adults. The objective was to test whether resilience (defined as process, capacity or outcomes) or adaptive functioning may moderate functional connectivity in the amygdala to other brain regions involved in higher-order cognitive functioning such as the frontal cortex in response to tasks involving emotional stimuli in adults who have experienced childhood maltreatment. The authors hypothesized that individuals who had been maltreated with low adaptive functioning scores (i.e. less resilient) would be more likely to have increased emotional-related connectivity between the amygdala and frontal cortex compared to individuals who have not been maltreated.
The sample of 80 adults was recruited through a summer camp program for high risk children who had been assessed during childhood prior to the adult assessment. Forty-one respondents had a history of childhood maltreatment (measured by official reports in administrative data) and by the Maternal Maltreatment Assessment Interview. Seventy percent of participants had experienced multiple forms of maltreatment and the event was linked to the developmental period of onset. A total of 41 participants were included in the maltreated group and 39 were in the non-maltreated group.
Adult Adaptive Functioning
The study used a composite measure of rank scores from the Adult Self Report Measure on seven domains of development: education, work, financial autonomy, romantic involvement, peer involvement, family involvement and substance abuse. The participants were ranked in the bottom middle or highest rank when compared to others in similar economic and social backgrounds.
Behavioural Task During Functional Imaging
Respondents were asked to do specific tasks while being imaged with functional MRI. The task was to select emotionally expressive (i.e. fearful/angry) faces or to select simple geometric shapes. The participants had to match the emotional faces by expression or shapes presented at the bottom of the screen to a target on the top of the screen. The images were presented on the screen for 4.5 seconds.
The participants lay still in the scanner for the duration of the experiment. An anatomical scan of each participant’s brain was acquired. During the presentation of the emotional faces and shapes task, blood flow changes in the brain, an indirect measure of neuronal activity, were captured using functional MRI.
The functional MRI scans were corrected for any head movements that may have occurred during the scans. Additionally, the functional activation in each participants scan was overlaid on the anatomical scan, thus permitting the identification of where in the brain the functional activity occurred. Lastly all the scans where registered into the same 3D MRI space. By registering the scans to the same 3D MRI space this allows investigators to average the activation seen across all participants. The results reflect the averaged group data.
Activity in the brain in response to the emotional faces and shapes was analyzed.
To assess activity in the brain in the mal-treated versus non mal-treated group, the activation in response to the emotional faces and shapes was directly compared.
To address the author’s hypotheses concerning the association of childhood maltreatment and adaptive functioning relative to the connectivity of the amygdala and the frontal cortex, a psychophysiological analysis was performed. Functional activation was extracted from the amygdala in response to the emotional faces relative to the shape-matching task. This would allow the researchers to examine emotion-related activation in the amygdala without confounding activation associated with viewing visual stimuli. The activation in the amygdala was assessed in relation to its functional connectivity with other brain regions. Specifically, brain regions that co-activated with the amygdala and the response to the emotional faces tasks were assessed. This type of analysis would highlight brain regions that are activated at the same time as the amygdala, an indirect measure of functional connectivity, and that are also associated with processing emotional stimuli.
Overall, the respondents were less successful in the emotion-matching compared with the shape matching task. Those that had experienced child maltreatment were less effective than their non-maltreated controls for the emotion-matching task. The authors hypothesized that the child maltreatment would be related to adult functioning and therefore predict emotion-related amygdala connectivity. This was not the case, suggesting that adults who had experienced child maltreatment but had high levels of adaptive functioning did not show significant differences in emotion-related amygdala connectivity. There were however differences between the connectivity in a brain region involved in working memory, the hippocampus, and the amygdala between the maltreated and non-maltreated groups.
Strengths: This sample included a comparison group that was carefully matched on socio-economic status and risk and adult adaptive functioning. The sample was followed prospectively and assessed using multiple domains. This meant that the authors could better assess the interactions between child maltreatment and resilience.
Weaknesses: The maltreatment experienced is not well defined. Although the developmental period of onset is included in the analysis there are missing respondents in the frequency table. Whether the respondent has experienced multiple forms of maltreatment was measured but the type of co-occurring maltreatment is not clear from the frequency table and the duration, frequency and severity of maltreatment were not measured. Functional imaging of the amygdala is technically very challenging as a small structure and it is located in an area of the brain that is difficult to image. The signal in this region may not have been particularly strong. In turn, some of the statistical analysis methods are difficult to interpret. Larger samples utilizing a robust functional neuroimaging protocol would be recommended for future studies in this area.