Change of Cognition Effects by Impact of the Transcranial Magnetic Stimulation

The purpose of this paper is to investigate the effects of sub- or supra-threshold low-frequency repetitive transcranial magnetic stimulation (rTMS) on cognitive function. The magnetic stimulation was delivered at 1 Hz to the left supramarginal gyrus, which is considered to be the area of origin of the P300 event-related potential component. The intensity of magnetic stimulation was 80% or 120% of motor threshold, and 100 magnetic pulses were applied. The auditory oddball task, consisting of tone burst waves, was used to elicit P300 before and shortly after magnetic stimulation. We found that P300 latency depended on the intensity of the 1 Hz magnetic stimulation. With subthreshold rTMS, P300 latency was significantly shortened compared with before magnetic stimulation by around 10 ms (Cz: p<;0.05) on average. With the suprathreshold rTMS, the latency was significantly delayed compared with before magnetic stimulation by around 10 ms (Cz: p<; 0.01) on average. The facilitation of cortical excitability by rTMS may induce the shortening of P300 latency, whereas the inhibition of cortical excitability may induce its delay. Thus, P300 latency can be altered by both sub- and supra-threshold low-frequency magnetic stimulation.