Discussion
D’Mello
EVENTS, CEREBELLAR FUNCTION, CORTEX
This study used tDCS and ACT to assess the contribution of the cerebellum to automatic (free-associative) versus controlled (inhibition, switching) semantic memory retrieval, respectively. We revealed that anodal cerebellar tDCS facilitated the retrieval of sequentially related concepts within the free-associative word chains but had no influence on the retrieval conditions that pose demands on semantic control, i.e., inhibition (delivery of unrelated words) or switching (flexible alternating between the retrieval rules). Our data thus indicate that the cerebellum is engaged in automatic rather than controlled retrieval from semantic memory. Furthermore, anodal cerebellar stimulation inhibited rather than facilitated response latencies in the simple choice reaction time task. Although the behavioral effects in this basic task were very small (but statistically significant), they rule out that the improved associative fluency was due to a non-specific (domain-general) acceleration in processing speed.There is abundant evidence that the cerebellum supports automatic processing and habit formation, which has been attributed to the so-called forward model of control implemented within the cortico-cerebellar neuronal circuitry (Wolpert et al. The effects of cerebellar stimulation on retrieving semantically related information may not be general, since the associative fluency was improved in the fixed but not the alternating chains. This difference may be due to the distinct feature of the alternating associative-dissociative task, in which each attempt to retrieve a semantically related word is preceded by a switch and therefore discontinued. Consequently, delivering associative responses in alternating chains represents isolated events, diminishing the benefit from ongoing consecutive pre-activation (i.e., forward activation) of the related representations within memory, afforded by the fixed chains. Furthermore, the cerebellar tDCS did not affect the latency of completing sentences, which may also exert demands on predictive semantic processing and conceptual access. Although this result apparently differs from some previous studies reporting positive effects of anodal cerebellar tDCS on the speed of sentence completion (D’Mello et al. The three groups in our study showed no statistically significant differences in baseline performance. Nevertheless, before stimulation, the fluency in the Associate Fixed condition of ACT was slowest in the anodal group, potentially raising question about the interpretation of the significant interaction between One matter of debate regarding the cerebellum is the lateralization of cerebellar functions. Although neuroimaging studies employing language tasks usually report stronger activation of the right than the left cerebellum, meta-analyses have confirmed the activations in both the right and the left cerebellar hemispheres (Stoodley and Schmahmann Notably, the results of the current study complement those from our previous experiment, which has shown that anodal tDCS of the left lateral prefrontal cortex facilitated dissociative performance in ACT but had no influence on retrieval of semantic associates, thus boosting controlled but not automatic semantic retrieval (Marko and Riečanský 