Interleaved premotor rTMS does not affect motor sequence learning.

Acquiring new motor skills is a vital component of lifelong learning and underpins everyday activities. Performance improvements through training evolve from an initially fragile state to one that becomes increasingly resistant to disruption, a process known as motor consolidation. Recent research has indicated that learning takes place even during brief periods of rest - termed micro-offline learning. In healthy young individuals, such intervals may represent the primary source of performance enhancements during training sessions. Other studies have identified both the primary motor cortex (M1) and the premotor cortex (PMC) as pivotal neural structures for motor consolidation. Specifically, it has been demonstrated that 10 Hz interleaved repetitive transcranial magnetic stimulation (i-rTMS) to M1 during rest intervals between active motor training blocks can enhance post-training offline consolidation without influencing performance during training. Here, we examined whether 10 Hz i-rTMS to the PMC produces similar effects. Contrary to our expectations, our results suggest that premotor i-rTMS does not affect online or offline learning, at both microscopic and macroscopic temporal scales. We also measured corticospinal excitability before and after training, but no detectable effects of training or i-rTMS were observed. Taken together, these findings provide no evidence for an effect of i-rTMS of the PMC on online or offline motor sequence learning. We speculate that consolidation during offline processing in short rest periods between active training phases may not necessarily require involvement of the premotor cortex.