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Keishi Nomura, Shuhei Shima, Kristina Visscher, Aaron Seitz, Yuko Yotsumoto; Effects of Transcranial Electric Stimulation to Early Visual Areas on Regional BOLD fMRI Activity During Visual Task. Journal of Vision 2018;18(10):250. doi: 10.1167/18.10.250.
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© ARVO (1962-2015); The Authors (2016-present)
Transcranial electric stimulation (tES) has attracted considerable interest due to its potential to improve our understanding of the relationship between brain activity and human behavior. While there is a vast amount of literature on the behavioral effects of tES, less is known about its effects on visual perception and how the underlying neural modulation is spatially and temporally organized at local neural circuit level. Here we applied tES to human early visual areas during a visual task, aiming to examine its effects on regional blood oxygen level-dependent (BOLD) activity and to compare the effects of different tES techniques. Twelve subjects participated in five fMRI sessions on five different days, during which different types of stimulation were delivered: transcranial direct current stimulation (tDCS), 10 Hz transcranial alternating current stimulation (tACS), high-frequency transcranial random noise stimulation (hf-tRNS), low-frequency transcranial random noise stimulation (lf-tRNS), and sham. We used the following electrode montage: anode over the Oz and cathode over the Cz. In each session, the subject underwent three 12-minute scans during an orientation discrimination task. tES was applied only during the second scan. Changes in the regional BOLD activity during stimulation (online effects) were defined as the contrast between task-driven activity during the second and first scans, and changes in the BOLD activity after stimulation (after-effects) were defined as the contrast between the third and first scans. 10 Hz tACS induced an increase in BOLD activity evoked by the task in the right inferior and middle temporal cortex, which are distant from the stimulation sites. No after-effect was observed. Other stimulation methods failed to show significant online or after effects detectable at a group level. These results support the idea that the effects of tACS at alpha frequency are not limited in stimulation sites and rather spread to large-scale visual networks.
Meeting abstract presented at VSS 2018
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