Electrical stimulation of the cerebellum facilitates automatic but not controlled word retrieval

Recent research has indicated that the cerebellum is engaged in language functions, yet the role of the cerebellum in lexical-semantic memory is poorly understood. In a double-blind randomized controlled experiment, we therefore targeted the cerebellum by transcranial direct current stimulation (tDCS) to assess and compare the contribution of the cerebellar processing to automatic and controlled retrieval of words in healthy adults (n = 136). Anodal cerebellar tDCS facilitated retrieval of semantically related words in free-associative chains, which was not due to a non-specific acceleration of processing speed. The stimulation had no influence on controlled word retrieval that employed inhibition or switching. The effect of cathodal tDCS was opposite to the anodal stimulation, but statistically non-significant. Our data show that the cerebellum is engaged extracting associative information from the system of semantic representations, established and strengthened/automated by learning, and indicates a domain-general role of this structure in automation of behavior, cognition and language.