Abstracts

Rationale: This study aimed to investigate the threshold of cortical electrical stimulation for functional brain mapping. Methods: We retrospectively analyzed data from 17 patients with medically intractable epilepsy who underwent 50 Hz cortical electrical stimulation for the functional mapping between October 2013 and May 2017. The symptoms induced by the stimulation and the thresholds of stimulation for these responses were evaluated. Results: Electrical cortical stimulation produces two effects: (a) a positive or (b) a negative phenomenon. The motor responses were observed in the stimulation of primary motor cortex (M1), supplementary motor area (SMA) and frontal eye field, and sensory responses in primary and secondary sensory cortex. As the negative responses, language impairment was observed in the stimulation of anterior (ALA), posterior (PLA) and basal temporal language areas (BTLA), the negative motor responses in premotor cortex (PM), posterior parietal cortex (PPC) and preSMA, hearing impairment in PPC, and impairment of spatial recognition in right PPC. The positive and sensory effects are induced by the significantly lower intensities than negative and motor responses, respectively. Conclusions: The electrical stimulation activates or interferes each cortical function with different thresholds.The present results would provide not only a practical guide for functional mapping, but also the hierarchal concept of processing in the brain. Funding: KAKENHI 16K10795 from the Japan Ministry of Education, Culture, Sports, Science and Technology (MEXT)