Time change of perceptual reversal of ambiguous figures by rTMS

Abstract

The aim of this study was to investigate the effect of stimulus frequency and number of pulses during rTMS (repetitive transcranial magnetic stimulation) on the phenomenon of perceptual reversal. Particularly, we focused on the temporal dynamics of perceptual reversal in the right SPL (superior parietal lobule), using the spinning wheel illusion. We measured the IRT (inter-reversal time) of perceptual reversal. To investigate whether stimulus frequency or the number of pulses is critical for the rTMS effect, we applied the following schedules over the right SPL and the right PTL (posterior temporal lobe): 0.25Hz 60 pulses, 0.25Hz 120pulses, 0.5Hz 120 pulses, and 1Hz 120 pulses biphasic rTMS at 90% of the resting motor threshold. As a control, we included a No-TMS condition. The results showed that rTMS with 0.25Hz 60 pulses over the right SPL caused shorter IRT. There were no significant differences between IRTs for rTMS with 0.25Hz 120 pulses, 0.5Hz 120 pulses or 1Hz 120 pulses over the right SPL. Comparing these results with those of a previous study, we found that an rTMS condition with 60 pulses causes shorter IRT; 240 pulses causes longer IRT; and 120 pulses does not change IRT. Therefore, when applying rTMS over the right SPL, the IRT of perceptual reversal is primarily affected by the number of pulses.

Multistable Perception and the Role of the Frontoparietal Cortex in Perceptual Inference

“…In particular, several studies stimulated the right parietal cortex by targeting electrode P4 of the international 10-20 EEG system, the location of which varies considerably among participants (de Graaf et al 2011, Sack et al 2009, although it appears closer, on average, to the posterior locus than to the anterior one (de Graaf et al 2011). This might explain why some such studies observed a reduced frequency of perceptual transitions for an ambiguous apparent motion stimulus following inhibitory TMS and an increased frequency following facilitatory TMS (Ge et al 2008, Nojima et al 2010see VanRullen et al 2008 for a potentially related finding), whereas a different study found no effect for an ambiguous SFM stimulus (de Graaf et al 2011).…”