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 applied over primary motor cortex. Methods: Phosphene threshold to a single TMS pulse was measured before and after application of either continuous or intermittent theta burst 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 motor cortex 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.