Brain-heart interaction in implicit emotional processing: unveiling the cerebellar role

Recent evidence emphasizes the cerebellar role in social functioning. Due to its connections with the limbic and autonomic systems, the cerebellum may have a role in social domain by mediating autonomic reactions during automatic stage of emotional processing, i.e. the emotion recognition (ER). As a marker of autonomic cardiovascular function, Heart-Rate Variability (HRV) offers an objective measure of emotional response and autonomic regulation during ER. The hypothesis is that modulating the cerebellar excitability by means of transcranial direct current stimulation (tDCS), may influence the functional interaction between cerebello-cerebral regions involved in autonomic regulation enhancing autonomic reactivity and ER ability. Twenty-six healthy participants were randomly assigned to cerebellar anodal or sham tDCS. Before and after stimulation, they completed the computerized Reading the Mind in the Eyes Test, assessing ER accuracy (ACC) and reaction times (RTs). HRV was recorded before, during, and after the task. A Wilcoxon signed ranks test was performed to compare behavioral and physiological measures before and after cerebellar tDCS by using a within-group design. Unexpectedly, a significant effect of sham stimulation was observed, as showed by significantly increased ACC and reduced RTs as well as increased RMSSD related to task. Implicit emotional processing may be sustained by a brain–heart interplay involving the cerebellum.