Effects of theta burst stimulation protocols on phosphene threshold

Objective: We investigated the effects on occipital cortex, of two newly developed methods of repetitive transcranial magnetic stimulation(rTMS): continuous and intermittent theta burst stimulation (cTBS and iTBS), that lead to long lasting changes in excitability when appliedover primary motor cortex.Methods: Phosphene threshold to a single TMS pulse was measured before and after application of either continuous or intermittent thetaburst stimulation (cTBS/iTBS; 600 total pulses at 80% phosphene threshold).Results: In our cohort, cTBS increased phosphene threshold by an average of 10%. In contrast, iTBS, which transiently increases motorcortex excitability, had no effect on phosphene threshold.Conclusions: cTBS can be applied successfully to non-motor areas of cortex, but iTBS may need modification to produce maximal effects.Significance: cTBS maybe a new useful tool in disorders characterized by an abnormal state of activity of the visual cortex