Brain Stimulation In Depth

Neuroscience Transcranial magnetic stimulation (TMS) is a noninvasive clinical method of stimulating the human brain, which has been tested for the treatment of depression and other neurological disorders. Depending on the stimulation protocol used, TMS can increase or decrease cortical excitability; however, how it does so is poorly understood. Benali et al. thus used electrophysiological recording techniques and immuno-histochemistry to analyze the changes that occur in the rat brain after different repetitive TMS protocols. They found that two theta-burst stimulation (TBS) protocols that in the past have been shown to modify human cortical excitability in opposite ways also affected rat cortical activity and protein expression. Although both intermittent and continuous TBS affected cortical inhibitory neuronal systems, the cell types affected, and thus the overall effects of the stimulation, differed. These findings sound a note of caution because such impairment of the cortical inhibitory system may also take place in the human cortex. They also raise the critical question of whether these novel and increasingly popular high-frequency TMS protocols are really safe for use in human cognitive or clinical neuroscience. J. Neurosci. 31 , 1193 (2011).