Effects of Cerebellar Repetitive Transcranial Magnetic Stimulation at Different Frequencies on Working Memory: An EEG Study.

BACKGROUND

The cerebellum serves as an important target for non-invasive cognitive regulation because of its involvement in diverse cognitive processes via cerebro-cerebellar circuits. However, the efficiency of repetitive transcranial magnetic stimulation (rTMS) in different cognitive behavior protocols remains elusive.

OBJECTIVE

To investigate changes in working memory and behavioral performance after different cerebellar rTMS to provide objective neurobiological guidance for optimizing cerebellar TMS parameters.

METHODS

A total of 75 healthy adult volunteers underwent rTMS at various frequencies (1, 5, 10, and 20 Hz) or received sham stimulation. Electroencephalogram recordings were captured in the resting state and 2-back working memory tasks, both before and after stimulation. Behavioral results, event-related potential (ERP) waveforms and spectrum, and brain network topology changes were compared among the groups and rTMS conditions.

RESULTS

Behavioral results significantly differed between the 5 Hz stimulation and sham groups. Analysis of ERP data suggested that 5 Hz stimulation significantly increased P150 amplitude compared with sham. Time-frequency analysis showed enhanced θ and α oscillations after 5 Hz stimulation, with α oscillations significantly higher than those in sham stimulation. Resting state brain network analysis demonstrated increased θ band global efficiency and whole brain local efficiency after 5 Hz stimulation. In contrast, 20 Hz stimulation only reduced the shortest path length. In the 5 Hz stimulation group, P150 amplitude and α oscillation were significantly correlated with the reaction time.

CONCLUSION

Taken together, rTMS at 5 Hz applied to the cerebellar Crus II region significantly enhances neural oscillatory activity and improves working memory.