CAUSAL INVOLVEMENT OF CEREBELLAR CRUS I IN WORKING MEMORY UPDATING: EVIDENCE FROM TMS–EEG AND BEHAVIOR

Growing evidence indicates that the posterior cerebellum contributes to higher-order cognition, particularly working memory; however, direct causal evidence of cerebello–prefrontal interactions in humans remains scarce. This study characterizes the effective connectivity between right cerebellar Crus I and the dorsolateral prefrontal cortex (DLPFC), a key region for working memory processes, using a combined TMS–EEG approach at rest. Single-pulse transcranial magnetic stimulation (TMS) was delivered over right Crus I while electroencephalography (EEG) was recorded to obtain TMS-evoked potentials (TEPs). Two control conditions were included: stimulation of left Crus I (intracerebellar control) and occipital cortex (cortical control). In addition, structural connectivity of cerebello–thalamo–cortical pathways was estimated using diffusion-based tractography, integrating effective and anatomical connectivity measures. Preliminary results show that right Crus I stimulation elicits reliable TEP components over prefrontal regions, with a significant amplitude increase at electrode F3, located over the left prefrontal cortex and contralateral to the cerebellar stimulation site. This response was greater compared to both control sites. Moreover, the magnitude of TEPs at F3 correlated with individual differences in white matter integrity along cerebello–thalamo–cortical tracts. These findings provide causal neurophysiological evidence that right cerebellar Crus I directly influences prefrontal networks associated with working memory. Together, the results support models proposing that the cerebellum forms part of domain-general cognitive networks and establish a mechanistic basis for understanding its contribution to working memory.