Study pinpoints neural changes from adversity

In a recent study published in JAMA Network Open, researchers assess the link between adversarial life experiences and changes in brain reactivity using the multilevel kernel density evaluation (MKDA) method on task-based functional magnetic resonance imaging (fMRI) studies.

Study: Opposed Life Experiences and Brain Function: A Meta-Evaluation of Functional Magnetic Resonance Imaging Findings. Image Credit: Tushchakorn / Shutterstock.com

Background 

Negative life experiences can alter brain functions, thereby increasing the chance of mental illnesses. The principal brain regions affected include the prefrontal cortex (PFC), amygdala, and hippocampus.

While animal studies confirm this, human data is variable as a result of differences in defining adversity, measuring its impact, and diverse study methods. Variability also arises from using different image acquisition and evaluation techniques.

A meta-analysis using the MKDA method, which accounts for these variations, provided more reliable insights than the activation likelihood estimation (ALE) method. Nevertheless, given the inconsistencies in human studies on brain responses to adversity, further research is important to grasp long-term neuroplastic changes from adversarial experiences.

In regards to the study 

The current study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guidelines. Comprehensive literature searches were performed across databases, including PsycINFO, Medline, EMBASE, and Web of Science, until May 2022. Additional searches within the Brainmap database and grey literature were also performed.

The search combined terms related to trauma, adversity, neuroimaging, and various cognitive processes. Articles were chosen based on specific criteria, which led to the exclusion of conference abstracts, books, and certain other sorts of publications.

From the initial 2,016 abstracts identified, 336 met the factors for a more in-depth review. Two reviewers assessed these articles, and a 3rd reviewer resolved any discrepancies.

Brain activation coordinate data were precisely extracted and verified. To elucidate the varied definitions of adversity across studies, these data were categorized based on criteria like threat or deprivation and by adversity severity.

For statistical evaluation, the researchers extracted activation coordinates and grouped them based on task type and participant groups. The MKDA method was used to find out whether activations were consistent across studies.

Simulations were used to confirm the authenticity of the findings. The info evaluation was conducted between August and November 2022 using specialized software tools.

Study findings 

In the excellent evaluation of 83 studies comprising 5,242 participants, significant variations in blood-oxygen-level-dependent (BOLD) responses were observed in relation to adversity exposure. When the info from 67 studies was examined, those exposed to adversity exhibited enhanced right amygdala responses as in comparison with their counterparts. Comparatively, 47 other studies showed that the adversity group displayed consistently diminished responses within the medial frontal gyrus.

Of the 50 studies on emotion processing, the adversity-exposed group exhibited heightened amygdala activity and reduced superior frontal gyrus activity. In 11 studies focused on inhibitory control, those that experienced adversity exhibited increased activity within the claustrum, anterior cingulate cortex, and insula. No difference was observed in studies about memory or reward-processing tasks.

When examining threats as adversity, there was amplified BOLD response within the superior temporal gyrus and decreased medial frontal gyrus activity for the adversity group. This pattern continued across different task domains.

When mixed sorts of adversities were studied, individuals exposed to those mixed adversities exhibited heightened activity across all domains in the best amygdala, precuneus, and superior frontal gyrus. In studies focusing solely on deprivation-type adversities, no significant results were reported, thus making definitive conclusions difficult.

Individuals exposed to trauma-type adversities exhibited significantly greater bilateral amygdala activation and reduced activity in areas just like the medial frontal gyrus and anterior cingulate cortex. Meanwhile, moderate adversities weren’t related to any significant associations.

The association between trauma and psychopathological conditions like post-traumatic stress disorder (PTSD) was also examined. To this end, individuals diagnosed with PTSD exhibited significantly greater left amygdala activation but diminished activity in regions just like the hippocampus, orbitofrontal cortex, and insula.

The study also considered developmental stages by categorizing participants into adults, adolescents, and kids. Adult data, which were extracted from 34 studies, revealed that adversity exposure during maturity was related to increased right amygdala activation but decreased activity in the center frontal gyrus.

Conclusions 

Individuals with a history of severe adversity have heightened amygdala responses and reduced PFC reactions to psychological challenges. MKDA of 83 studies showed potential PFC impairment in regulating amygdala activity.

The amygdala, which is important for threat detection, exhibited increased activity as a PTSD biomarker. Individuals with PTSD or those that experienced severe adversities exhibited more robust amygdala and weaker PFC responses across tasks.

Specific adversities increased insula and anterior cingulate cortex (ACC) activity. Traumatic adversities particularly enhanced amygdala activity.

Notably, individuals with PTSD exhibited significant left amygdala activity, which contrasts with some earlier studies, and decreased activity in other brain regions.