New Horizons on Non-invasive Brain Stimulation of the Social and Affective Cerebellum.

The cerebellum is increasingly attracting scientists interested in basic and clinical research of neuromodulation. Here, we review available studies that used either transcranial magnetic stimulation (TMS) or transcranial direct current stimulation (tDCS) to examine the role of the posterior cerebellum in different aspects of social and affective cognition, from mood regulation to emotion discrimination, and from the ability to identify biological motion to higher-level social inferences (mentalizing). We discuss how at the functional level the role of the posterior cerebellum in these different processes may be explained by a generic prediction mechanism and how the posterior cerebellum may exert this function within different cortico-cerebellar and cerebellar limbic networks involved in social cognition. Furthermore, we suggest to deepen our understanding of the cerebro-cerebellar circuits involved in different aspects of social cognition by employing promising stimulation approaches that have so far been primarily used to study cortical functions and networks, such as paired-pulse TMS, frequency-tuned stimulation, state-dependent protocols, and chronometric TMS. The ability to modulate cerebro-cerebellar connectivity opens up possible clinical applications for improving impairments in social and affective skills associated with cerebellar abnormalities.

Rubber Hand Illusion survives Ventral Premotor area inhibition: A rTMS study.

The sense of body ownership is a fundamental feature that refers to the ability to recognize our body as our own, allowing us to interact properly with the outside world. Usually, it is explored by means of the Rubber Hand Illusion (RHI) during which a dummy hand is incorporated in the mental representation of one's own body throughout a multisensory (visuo-tactile) integration mechanism. Particular attention has been paid to the neurofunctional counterparts of this mechanism highlighting the pivotal role of an occipito-parieto-frontal network involving the Ventral Premotor area (PMv). To date, the specific role of the PMv in generating the sense of ownership is still unknown. In this study, we aimed at exploring the role of PMv in generating and experiencing the RHI. Off-line repetitive Transcranial Magnetic Stimulation (rTMS) was applied to a group of 24 healthy participants whilst changes in proprioceptive judgment and self-reported illusion sensations were collected and analysed separately. The PMv was not directly implicated in generating the sense of ownership. Indeed, its inhibition affected the explicit detection of the visuo-tactile congruence without interfering with the illusion experience itself. We hypothesized that the conscious visuo-tactile congruence detection may be independent from the conscious illusion experience. Also, our results support the view that the RHI grounds on a complex interaction between bottom-up and top-down processes, as the visuo-tactile integration per se may be not sufficient to trigger the subjective illusion.