The influence of M1 and DLPFC iTBS on BCI performance: A TMS and fNIRS study

Many stroke survivors are unable to effectively control brain-computer interface (BCI) devices due to insufficient sensorimotor activity generated during motor imagery. Previous studies focused on upregulating motor cortex excitability and overlooked the important role that motor imagery plays on BCI control. Dorsolateral prefrontal cortex (DLPFC), an important region for motor imagery, may serve as an effective target for improving BCI performance. This study is aimed at investigating how intermittent theta burst stimulation (iTBS) targeted on primary motor cortex (M1) and DLPFC influences BCI performance and its neural mechanisms. Twenty-five healthy subjects received four types of iTBS (i.e., M1 iTBS, DLPFC iTBS, combination of M1 and DLPFC iTBS and sham iTBS) in a random order. BCI control testing, functional near-infrared spectroscopy assessment and single-pulse transcranial magnetic stimulation were performed before and immediately after iTBS in each session. Corticospinal excitability, brain activation, and functional connectivity were calculated. Our results revealed that corticospinal excitability was significantly increased after M1 iTBS (P=0.016), with the magnitude of increase positively correlated with changes in BCI performance (P=0.013). Frontoparietal network functional connectivity was significantly increased after DLPFC iTBS (P\u2019s\uff1c0.05), with the magnitude of increase positively correlated with changes in BCI performance (P\u2019s\uff1c0.05). In conclusion, M1 iTBS could improve BCI performance via increasing corticospinal excitability, whereas DLPFC iTBS could improve BCI performance via increasing frontoparietal network functional connectivity. These findings may inform the development of new treatment for neurological populations to improve BCI performance and be more engaged in BCI training.