Cerebellar Grey Matter Volumes in Reactive Aggression and Impulsivity in Healthy Volunteers

Cerebellar Asymmetry of Motivational Direction: Anger-Dependent Effects of Cerebellar Transcranial Direct Current Stimulation on Aggression in Healthy Volunteers

It has recently been theorized that the frontal asymmetry of approach- and avoidance-related motivation is mirrored in the posterolateral cerebellum. Accordingly, left-to-right dominant cerebellar activity is associated with avoidance-related motivation, whereas right-to-left dominant cerebellar activity is associated with approach-related motivation. The aim of this study was to examine the cerebellar asymmetry of motivational direction in approach-related behavior in the context of aggression. In this randomized double-blind sham-controlled crossover study, thirty healthy right-handed adult volunteers received 2 mA active or sham left cathodal-right anodal transcranial direct current stimulation (tDCS) to the cerebellum on two separate occasions while engaging in the Point Subtraction Aggression Paradigm (PSAP) task to measure aggressive behavior. Self-reported state anger was assessed before, halfway and immediately after the task, and heart rate and heart rate variability (HRV) were measured during the task. No main effects of tDCS on aggressive behavior, heart rate and HRV were found. Higher state anger before and during the PSAP task was associated with increased aggressive behavior in the active compared to sham tDCS condition. Aggressive behavior was positively correlated with heart rate during active tDCS, while an inverse association was observed during sham tDCS. Results provide support for the cerebellar asymmetry of motivational direction in approach-related behavior and illustrate the importance of affective state-dependency in tDCS-related effects.

The contribution of brain volume to explain autonomous imbalance during recovery from acute stress in batterers

AIM

Many authors have suggested that intimate partner violence (IPV) perpetrators present an imbalance between both branches of the autonomous nervous system when coping with acute stress. Concretely, there is a predominance of the sympathetic branches over the parasympathetic ones when recovering from stress. This imbalance can be explained by their tendency toward anger rumination, and more concretely, by their focus on thoughts of revenge during this period. Unfortunately, there is a gap in the scientific literature in terms of using magnetic resonance imaging (MRI) techniques to assess which brain structures would explain this tendency of IPV perpetrators when coping with acute stress.

METHOD

The main objective of this study was to assess whether the gray matter volume (GMV) of relevant brain structures, signaled in previous scientific literature, moderates the association between thoughts of revenge and sympathetic activation during the recovery period, based on skin conductance levels (SCL) after being exposed to stress, in a group of IPV perpetrators (n = 58) and non-violent men (n = 61).

RESULTS

This study highlighted that the GMV of the left nucleus accumbens, right lobules of the cerebellum, and inferior temporal gyrus in IPV perpetrators moderated the association between thoughts of revenge and SCL during the recovery period. Accordingly, the higher the thoughts of revenge, the higher the sympathetic predominance (or higher SCL levels), especially among IPV perpetrators with the lowest GMV of these brain structures. Nonetheless, those variables were unrelated in the control group.

CONCLUSIONS

Our study highlights the involvement of certain brain structures and how they explain the tendency of some IPV perpetrators to ruminate anger or, more precisely, to focus on thoughts of revenge when they recover from acute stress. These results reinforce the need to incorporate neuroimaging techniques during screening processes to properly understand how IPV perpetrators deal with stress, which in turn helps target their needs and design concrete intervention modules.

Lower cerebello-cortical functional connectivity in veterans with reactive aggression symptoms: A pilot study

A significant number of veterans experience irritability and aggression symptoms as a result of being exposed to extremely stressful and life-threatening situations. In addition to the well-established involvement of the brain's cortico-subcortical circuit in aggression-related behaviours, a role of the deep cerebellar nuclei (DCN) in reactive aggression has been suggested. In the present study, seed-based resting-state functional connectivity between the DCN and cortico-subcortical areas was explored in veterans with and without reactive aggression symptoms. Nineteen male veterans with reactive aggression symptoms and twenty-two control veterans without reactive aggression symptoms underwent 3T resting-state functional MRI scans. Region-of-interest (ROI) analyses that included the amygdala, hypothalamus and periaqueductal grey as ROIs did not yield significant group-related differences in resting-state functional connectivity with the DCN. However, exploratory whole-brain analysis showed that veterans with reactive aggression symptoms exhibited lower functional connectivity between the DCN and the orbitofrontal cortex compared to control veterans. Our findings provide preliminary evidence for the possible involvement of a cerebello-prefrontal pathway in reactive aggression in male veterans.