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 human cerebellum in reward anticipation and outcome processing: An activation likelihood estimation meta-analysis.

The cerebellum generates internal prediction models and actively compares anticipated and actual outcomes in order to reach a desired end state. In this process, reward can serve as a reinforcer that shapes internal prediction models, enabling context-appropriate behavior. While the involvement of the cerebellum in reward processing has been established in animals, there is no detailed account of which cerebellar regions are involved in reward anticipation and outcome processing in humans. To this end, an activation likelihood estimation meta-analysis of functional neuroimaging studies was performed to investigate cerebellar functional activity patterns associated with reward anticipation and outcome processing in healthy adults. Results showed that reward anticipation (k = 31) was associated with regional activity in the bilateral anterior lobe, bilateral lobule VI, left Crus I and the posterior vermis, while reward outcome (k = 16) was associated with regional activity in the declive and left lobule VI. These findings demonstrate distinct involvement of the cerebellum in reward anticipation and outcome processing as part of a predictive coding routine.