Hypnotisability and the Cerebellum: Hypotheses and Perspectives

Hypnotisability is a multidimensional trait predicting the proneness to enter hypnosis and/or accept suggestions and is associated with several psychophysiological correlates. This scoping review reports the differences between individuals with high (highs) and low hypnotizability (lows) in the left cerebellar lobules IV–VI grey matter volume, in the excitability of the right motor cortex and in motor and non-motor functions in which the cerebellum may be involved. A reduced cerebellar inhibition may explain the greater excitability of the highs’ right motor cortex. The latter may be involved in their greater proneness to ideomotor behaviour following sensorimotor suggestions. The associated experience of involuntariness and effortlessness could be due to the motor cortex greater excitability as well as to activation of a specific cerebellar-parietal circuit. Looser postural and visuomotor control with no learning across trials and greater attentional stability can be accounted for by a less accurate cerebellar predictive model of information processing. The highs’ stronger functional equivalence between imagery and perception/action and greater motor excitability may be involved in the highs’ greater proneness to respond to emotional stimuli. Paradoxical pain control may depend on reduced cortical inhibition of the pain matrix by the cerebellum. Cerebellar hypotheses are not alternative to other physiological mechanisms and should be tested in future research.

Downbeat nystagmus in cerebellitis: The cerebellar inhibition to the vestibulo-ocular reflex

Downbeat nystagmus occurs as a result of an impaired vestibulo-ocular reflex1. From animal experiments, the Purkinje cells of the flocculonodular and parafloccular lobes of the cerebellum (also known as the “vestibular cerebellum”) are known to negatively regulate the upward rotation of the eyes via feed-forward inhibitory neural circuitry to the vertical vestibulo-ocular reflex [Supplemental figure 1,links.lww.com/CPJ/A199) 2. Although various eye movement abnormalities have been described in congenital and acquired cerebellar disorders, there have been few reports of pure downbeat nystagmus in cerebellitis.Here we report a quite impressive pure downbeat nystagmus in an adolescent female with acute cerebellitis. The electro-oculography of the patient provided compelling evidence that the downbeat nystagmus is indeed the result of feed-forward inhibition to the vestibulo-ocular reflex. Our case may add new insights into the current literature on cerebellar control of eye movement.

Neck muscle fatigue impacts plasticity and sensorimotor integration in cerebellum and motor cortex in response to novel motor skill acquisition

Normally motor learning decreases cerebellar inhibition (CBI) to facilitate learning of a novel skill. In this study, neck fatigue before motor skill acquisition led to less of a decrease in CBI and significantly less improvement in performance accuracy relative to a control group. This study demonstrated that neck fatigue impacts the cerebellar-motor cortex interaction to distal hand muscles, a highly relevant finding due to the altered neck postures and fatigue accompanying increased technology use.

Effects of Cerebellar tDCS on Inhibitory Control: Evidence from a Go/NoGo Task

Response inhibition as an executive function refers to the ability to suppress inappropriate but prepotent responses. Several brain regions have been implicated in the process underlying inhibitory control, including the cerebellum. The aim of the present study was to explore the role of the cerebellum in executive functioning, particularly in response inhibition. For this purpose, we transitorily inhibited cerebellar activity by means of cathodal tDCS and studied the effects of this inhibition on ERP components elicited during a Go/NoGo task in healthy subjects. Sixteen healthy subjects underwent a Go/NoGo task prior to and after cathodal and sham cerebellar tDCS in separate sessions. A reduction in N2-NoGo amplitude and a prolongation in N2-NoGo latency emerged after cathodal tDCS whereas no differences were detected after sham stimulation. Moreover, commission errors in NoGo trials were significantly higher after cathodal tDCS than at the basal evaluation. No differences emerged between performances in Go trials and those after sham stimulation. These data indicate that cerebellar inhibition following cathodal stimulation alters the ability to allocate attentional resources to stimuli containing conflict information and the inhibitory control. The cerebellum may regulate the attentional mechanisms of stimulus orientation and inhibitory control both directly, by making predictions of errors or behaviors related to errors, and indirectly, by controlling the functioning of the cerebral cortical areas involved in the perception of conflict signals and of the basal ganglia involved in the inhibitory control of movement.