Effects of high frequency repetitive transcranial magnetic stimulation on P300 event-related potentials

Objective: Auditory event-related potentials (P300-ERPs) were analyzed before and after repetitive transcranial magnetic stimulation (rTMS). Methods: Two rTMS trains (10 Hz, 3 s, 100% motor threshold and 5 min interval) were delivered over the left frontal area in healthy subjects. P300-ERPs were recorded at 14 electrode sites on the scalp using a typical oddball paradigm before and after rTMS. The latencies and amplitudes of N100, P200, N200 and P300 were measured and compared. The directed coherence (DCOH) was estimated to demonstrate information flow between different cortical areas. Results: rTMS significantly influenced P300-ERPs. The effects differed on the different components (P<0.001). The latency of P300 significantly increased after stimulation, which was more obvious in the frontal and central areas. The changes in P300 amplitude were not significant (P>0.05). The DCOH from the frontal, central, parietal and occipital areas to the temporal area was significantly higher than the DCOH from the temporal area to the former 4 areas (P<0.01). Conclusions: rTMS with the present parameters can affect P300-ERPs, leading to a delayed P300 component and changes in information connections around the stimulated site. Our data suggest that rTMS may postpone neuronal activities related to cognitive processing.