Yuichiro Shirota1, Ristuko Hanajima2, Shinya Ohminami3, Ryosuke Tsutsumi3, Yoshikazu Ugawa4, Yasuo Terao5. 1. Department of Neurology, Division of Neuroscience, Graduate School of Medicine, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan. Electronic address: yshirota-tky@umin.ac.jp. 2. Department of Neurology, Division of Neuroscience, Graduate School of Medicine, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan; Division of Neurology, Department of Brain and Neurosciences, Faculty of Medicine, Tottori University 36-1 Nishi-cho, Yonago-shi, Tottori-ken, 683-8503, Japan. 3. Department of Neurology, Division of Neuroscience, Graduate School of Medicine, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan. 4. Department of Neuro-Regeneration, Fukushima Medical University, 1 Hikariga-oka, Fukushima City, Fukushima, 960-1295, Japan. 5. Department of Neurology, Division of Neuroscience, Graduate School of Medicine, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan; Department of Cell Physiology, Kyorin University 6-20-2 Shinkawa, Mitaka-shi, Tokyo, 181-8611, Japan.
Abstract
BACKGROUND: The masked-priming paradigm is used to test unconscious inhibitory processes of the brain. A tendency towards responses that are incompatible with the prime, designated as negative compatibility effect (NCE), emerges when the perception of a priming visual stimulus is "masked" afterwards. This effect presumably stems from a subliminal inhibitory process against the masked-prime. Prior lesions as well as activation studies suggest a key role of SMA in this effect. OBJECTIVE: This study was conducted to elucidate a causal role of SMA in the subliminal response inhibition represented by the NCE. METHODS: Using a repeated-measures pre-post design with a group of healthy people, physiological measures (resting and active motor thresholds and motor evoked potential (MEP) amplitude) and behavioral ones (choice reaction time (CRT), positive compatibility effect (PCE) and NCE) were obtained before and after three quadripulse stimulation (QPS), namely sham, M1-QPS, and SMA-QPS, on different days. CRT and PCE served as indices for different aspects of motor execution. RESULTS: Motor thresholds were not altered after any QPS, although the M1-QPS increased MEP amplitude. Neither CRT nor PCE was altered significantly after QPS protocols. NCE was abolished after the SMA-QPS. CONCLUSIONS: Abolished NCE after the SMA-QPS in the absence of MEP changes suggests that (1) SMA plays a cardinal role in the NCE, and (2) the network involved in NCE is different from that of MEP generation.
BACKGROUND: The masked-priming paradigm is used to test unconscious inhibitory processes of the brain. A tendency towards responses that are incompatible with the prime, designated as negative compatibility effect (NCE), emerges when the perception of a priming visual stimulus is "masked" afterwards. This effect presumably stems from a subliminal inhibitory process against the masked-prime. Prior lesions as well as activation studies suggest a key role of SMA in this effect. OBJECTIVE: This study was conducted to elucidate a causal role of SMA in the subliminal response inhibition represented by the NCE. METHODS: Using a repeated-measures pre-post design with a group of healthy people, physiological measures (resting and active motor thresholds and motor evoked potential (MEP) amplitude) and behavioral ones (choice reaction time (CRT), positive compatibility effect (PCE) and NCE) were obtained before and after three quadripulse stimulation (QPS), namely sham, M1-QPS, and SMA-QPS, on different days. CRT and PCE served as indices for different aspects of motor execution. RESULTS: Motor thresholds were not altered after any QPS, although the M1-QPS increased MEP amplitude. Neither CRT nor PCE was altered significantly after QPS protocols. NCE was abolished after the SMA-QPS. CONCLUSIONS: Abolished NCE after the SMA-QPS in the absence of MEP changes suggests that (1) SMA plays a cardinal role in the NCE, and (2) the network involved in NCE is different from that of MEP generation.