Oksipital Korteks Uyarılabilirliğinin Transkraniyal Manyetik Uyarım ile Modulasyonu

Abstract

Visual cortical structures are the brain regions that is frequently investigated than the other non-motor cortical structures in terms of excitability due to its many complex connectivity. It is possible to modulate physiological responses by repetitive transcranial magnetic stimulation. In this study; we aimed to investigate the neurophysiological effect of transcranial magnetic stimulation continuous theta burst stimulation protocol, which is a painless, non-invasive method, over visual brain region in healthy individuals. Twenty-five (15 female,10 male) 29.84  4.7 average-aged healthy individuals were included in sham and real c TBS occipital stimulation sessions. Before and after each application, neurophysiological studies including phosphene threshold determination and visual evoked potential responses were performed. The N75, P100 latency values and maximum amplitude values between N75-P100 peaks were measured over the mean values of the responses of uninterrupted blocks, using one thousand continuous visual stimuli for VEPs. The parameters of the first VEP block, the fifth VEP block and the tenth VEP block were compared. The amplitude ratios of the first and tenth blocks were considered as habituation parameters. There was no difference between the N75, P100 latencies and N75-P100 amplitude values in the sham and real c TBS sessions of the individuals. VEP habituation was observed in both sessions in individuals, but it did not reach statistical significance after c TBS session. The phosphene threshold values were significantly lower after sham session and the threshold values increased to statistically significant levels after the real c TBS session. It was concluded that the excitability of the occipital cortex can be modulated by inhibiting the application of c TBS, and that the phosphene threshold value is a more effective parameter than VEP habituation to follow up the changes.