Reproducing the facilitatory effects of transcranial random noise stimulation on motion processing

Authors

• R Ruhde
• MB Carroll
• G Edwards
• CI Baker

Abstract

Transcranial random noise stimulation (tRNS) is a form of noninvasive electrical brain stimulation where an alternating current is passed between electrodes at random frequencies. High-frequency tRNS (hf-tRNS) is thought to enhance excitability and has been reported to have facilitatory effects on behavior in healthy and clinical populations. Clear demonstrations of the efficacy and replicability of stimulation are critical. Here, we seek to replicate the facilitatory effect of hf-tRNS over the human middle temporal complex (hMT+) on contralateral motion processing, initially demonstrated by Ghin et al. (2018). The reported improvement in performance was specific to global motion processing in the visual field contralateral to stimulation. We used a within-participants design in which each participant (n=42) completes a global motion discrimination task during three stimulation conditions: active hf-tRNS targeting hMT+, sham hf-tRNS targeting hMT+, and an active control hf-tRNS applied to the forehead. Following Ghin et al. (2018), hMT+ was localized using anatomical landmarks (3 cm dorsal of inion and 5 cm leftward). We analyze the motion coherence threshold in the contralateral visual field relative to the ipsilateral visual field to test for a decrease in the contralateral field threshold in response to stimulation. We are also investigating the effect of stimulation targeting hMT+ relative to sham and active forehead control conditions. Finally, we included a functional MRI localizer of hMT+ to explore the overlap between the simulated e-field of the anatomically and functionally localized hMT+ to determine if an increased overlap predicts increased behavioral response to stimulation.

Scientific Focus Area: Neuroscience

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