Relationship between pulse number of rTMS and inter reversal time of perceptual reversal

The aim of this study is to investigate the stimulus parameter which affects the repetitive Transcranial Magnetic Stimulation (rTMS) effect. It is said that the condition under 1Hz rTMS induces the inhibition effect. On the other hand, the condition over 1 Hz rTMS induces the facilitation effect. However the number of pulses of rTMS is also important factor. In this study, we focused on the number of pulses. We used the cognitive task of perceptual reversal and compared the rTMS effects of different condition under 1 Hz which is the inhibition condition. It has been known that the right superior parietal lobule (SPL) has a role in perceptual reversal. We applied rTMS over the SPL and measured the inter-reversal time (IRT) of perceptual reversal. The results showed that when 0.25 Hz 60 pulses, 0.5 Hz 60 pulses and 1 Hz 60 pulses of rTMS was applied over the right SPL, the IRT was significantly smaller. On the other hand, when 1 Hz 240 pulses of rTMS was applied over the right SPL, the IRT was significantly longer. When 0.25 Hz 12 0 pulses, 0.5 Hz 120 pulses and 1Hz 120 pulses of rTMS was applied over the right SPL, there were no significant differences. Furthermore, to investigate the rTMS effects, when rTMS are applied over the motor area, we measured the motor evoked potential (MEP). The more pulses of rTMS was applied, the smaller the amplitude of MEP became. From these results, it was found that the IRT of perceptual reversal and the amplitude of MEP primarily affected by the number of pulses of rTMS.