Investigating the role of cerebellum in semantic memory: a transcranial magnetic stimulation study

In recent years, the research on memory shifted with the advancement of the idea that memory is oriented towards the future by making predictions. Human cerebellum is one of the areas active during both retrieval of past experiences and imagining future scenarios, suggesting its role in the predictive scheme of memory. Previously, the cerebellum has been mainly associated with motor functions, but recent evidence suggested its role in cognitive processing, including semantic prediction. However, no evidence about cerebellar role in semantic memory is available. In order to test whether the cerebellum is involved in semantic memory, we performed an experiment in which participants were requested to judge if the noun-adjective word-pairs showed were meaningful (e.g. fresh tomato) or not meaningful (e.g. blue lemon), while online transcranial magnetic stimulation (TMS) was administered over the right cerebellum and over the vertex (control site). Additionally, all participants also performed the perceptual control task in which they were asked to differentiate random strings of letters while the same TMS protocol was applied. Cerebellar TMS had different effects on participants’ performances depending on stimulation timing. Compared with control stimulation, when cerebellar TMS was delivered at the onset of the first stimulus (noun), participants were significantly faster; while when cerebellar TMS was delivered at the onset of the second stimulus (adjective), participants’ accuracy was impaired. No effects were found during the control task. Results supports the idea that the cerebellum is involved in semantic memory. Results are discussed through the dysmetria of thought hypothesis and recent perspectives on predictive memory.