Hisato Nakazono1, Katsuya Ogata2, Akinori Takeda3, Emi Yamada3, Takahiro Kimura4, Shozo Tobimatsu3. 1. Department of Clinical Neurophysiology, Neurological Institute, Faculty of Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, 812-8582, Japan; Department of Occupational Therapy, Faculty of Medical Science, Fukuoka International University of Health and Welfare, Fukuoka, 814-0001, Japan. Electronic address: nakazono@med.kyushu-u.ac.jp. 2. Department of Clinical Neurophysiology, Neurological Institute, Faculty of Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, 812-8582, Japan; Department of Speech and Hearing Sciences, School of Health Sciences at Fukuoka, International University of Health and Welfare, Fukuoka, 831-8501, Japan. 3. Department of Clinical Neurophysiology, Neurological Institute, Faculty of Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, 812-8582, Japan. 4. Institute of Liberal Arts and Science, Kanazawa University, Kanazawa, 920-1192, Japan.
Abstract
BACKGROUND: Transcranial alternating current stimulation (tACS) can entrain and enhance cortical oscillatory activity in a frequency-dependent manner. In our previous study (Nakazono et al., 2016), 20 Hz (β) tACS significantly increased excitability of primary motor cortex compared with 10 Hz (α) tACS. α oscillations are a prominent feature of the primary visual cortex (V1) in a resting electroencephalogram. Hence, we investigated whether α and β tACS can differentially influence multiple visual functions. METHODS: Firstly, we evaluated the after-effects of α and β tACS on pattern-reversal (PR) and focal-flash (FF) visual evoked potentials (VEPs). Secondly, we determined the relationship between resting α oscillations and PR-VEPs modulated by tACS. Thirdly, the behavioral effects of tACS were assessed by contrast sensitivity. RESULTS: α tACS modulated the amplitudes of PR-VEPs, compared with β tACS, but did not modulate the FF-VEPs. Time-frequency analysis revealed that α tACS facilitated event-related α phase synchronizations without increasing power, which consequently increased the PR-VEP amplitudes. There was a significant positive correlation between PR-VEP amplitudes and resting α oscillations. These findings suggested that α tACS modulated α oscillations, and affected visual functions of contrast and spatial frequency. Indeed, α tACS also improved subjects' contrast sensitivity at the behavioral level. Conversely, β tACS increased posterior α activity, but did not change VEP amplitudes. CONCLUSIONS: α tACS can influence different neuronal populations from those influenced by β tACS. Thus, our results provide evidence that α tACS sharpens multiple visual functions by modulating α oscillations in V1.
BACKGROUND: Transcranial alternating current stimulation (tACS) can entrain and enhance cortical oscillatory activity in a frequency-dependent manner. In our previous study (Nakazono et al., 2016), 20 Hz (β) tACS significantly increased excitability of primary motor cortex compared with 10 Hz (α) tACS. α oscillations are a prominent feature of the primary visual cortex (V1) in a resting electroencephalogram. Hence, we investigated whether α and β tACS can differentially influence multiple visual functions. METHODS: Firstly, we evaluated the after-effects of α and β tACS on pattern-reversal (PR) and focal-flash (FF) visual evoked potentials (VEPs). Secondly, we determined the relationship between resting α oscillations and PR-VEPs modulated by tACS. Thirdly, the behavioral effects of tACS were assessed by contrast sensitivity. RESULTS: α tACS modulated the amplitudes of PR-VEPs, compared with β tACS, but did not modulate the FF-VEPs. Time-frequency analysis revealed that α tACS facilitated event-related α phase synchronizations without increasing power, which consequently increased the PR-VEP amplitudes. There was a significant positive correlation between PR-VEP amplitudes and resting α oscillations. These findings suggested that α tACS modulated α oscillations, and affected visual functions of contrast and spatial frequency. Indeed, α tACS also improved subjects' contrast sensitivity at the behavioral level. Conversely, β tACS increased posterior α activity, but did not change VEP amplitudes. CONCLUSIONS: α tACS can influence different neuronal populations from those influenced by β tACS. Thus, our results provide evidence that α tACS sharpens multiple visual functions by modulating α oscillations in V1.
Authors: Julius Kricheldorff; Katharina Göke; Maximilian Kiebs; Florian H Kasten; Christoph S Herrmann; Karsten Witt; Rene Hurlemann Journal: Brain Sci Date: 2022-07-15