Temporal Pattern-Dependent Cerebellar Involvement in Conflict Processing: An Online Transcranial Magnetic Stimulation Study.

INTRODUCTION

The cerebellum is increasingly recognized as a key contributor to cognitive control through interactions with distributed cerebello-cortical networks. Although online transcranial magnetic stimulation (TMS) has demonstrated a causal role for the cerebellum in executive functions, it remains unknown whether conflict processing depends on brief, discrete cerebellar computations or on sustained processing across extended temporal windows.

OBJECTIVE

To investigate whether temporally extended cerebellar stimulation (triple pulses at 20 Hz) produces greater disruption of conflict processing than single-pulse when applied online during the Eriksen flanker task.

METHODS

Forty-two healthy participants performed the Eriksen flanker task while receiving online TMS over the cerebellum and vertex control site. Three Pulse Patterns were tested: triple-pulse (20 Hz), single-pulse, and no-TMS baseline. Single pulses were delivered at 150 ms post-stimulus; triple pulses were delivered at 20 Hz starting at the same latency. Reaction times (RT) and interference scores were analyzed using repeated-measures ANOVAs and paired-samples t-tests. A difference-in-differences approach quantified the incremental effect of triple-pulse over single-pulse at each site.

RESULTS

The flanker task induced response conflict, with incongruent trials significantly slower than congruent trials. Cerebellar triple-pulse stimulation significantly increased RTs compared to cerebellar no-TMS, whereas cerebellar single-pulse showed smaller effects. Vertex stimulation produced no significant effects. Interference scores showed an incremental pattern for cerebellar stimulation while vertex interference scores remained stable.

CONCLUSION

Temporally extended cerebellar stimulation was associated with greater disruption of conflict processing than single-pulse stimulation in planned contrasts, a pattern consistent with the possibility that cerebellar contributions to cognitive control extend across a temporal window rather than being confined to a single discrete moment. Because the triple-pulse and single-pulse conditions differed in total pulse number, stimulation dose, and onset latency, this behavioral finding should be interpreted as consistent with, rather than proof of, sustained cerebellar processing.