Altering a complex serial reaction time task using dual DLPFC and M1- transcranial direct current stimulation

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique which was found to have a positive modulatory effect on online sequence acquisition or offline motor consolidation, depending on the relative role of the associated brain region. Primary motor regions (M1) and dorsolateral prefrontal cortices (DLPFC) have both been related to sequential learning. However, research so far did not systematically disentangle their differential roles in online and offline learning especially in more complex sequential paradigms. In this study, the influence of M1-tDCS and DLPFC-tDCS on complex sequential learning (online and offline) was investigated using a complex whole body serial reaction time task (CWB-SRTT) in 42 healthy volunteers. TDCS groups did not differ from sham tDCS group regarding their total time to complete the sequence and reaction time (online) and also not in terms of over-night consolidation (offline). Results may be related to unspecific parameters such as timing of the stimulation or current intensity but can also be attributed to the relative role of M1 and DLPFC during early complex learning. Future studies should consider investigating neural parameters during early complex CWB-SRTT learning to gain information on changes in neural activation within sequence acquisition with a specific focus on M1 and DLPFC.