Andrea Guerra1, Francesco Asci1, Alessandro Zampogna2, Valentina D'Onofrio2, Alfredo Berardelli3, Antonio Suppa4. 1. IRCCS Neuromed, Via Atinense 18, 86077 Pozzilli, IS, Italy. 2. Department of Human Neurosciences, Sapienza University of Rome, Viale dell'Università 30, 00185 Rome, Italy. 3. IRCCS Neuromed, Via Atinense 18, 86077 Pozzilli, IS, Italy; Department of Human Neurosciences, Sapienza University of Rome, Viale dell'Università 30, 00185 Rome, Italy. Electronic address: alfredo.berardelli@uniroma1.it. 4. IRCCS Neuromed, Via Atinense 18, 86077 Pozzilli, IS, Italy; Department of Human Neurosciences, Sapienza University of Rome, Viale dell'Università 30, 00185 Rome, Italy.
Abstract
OBJECTIVE: In healthy subjects, the long-term potentiation (LTP)-like plasticity of the primary motor cortex (M1) induced by intermittent theta-burst stimulation (iTBS) can be boosted by modulating gamma (γ) oscillations through transcranial alternating current stimulation (tACS). γ-tACS also reduces short-interval intracortical inhibition (SICI). We tested whether the effects of γ-tACS differ between young (YA) and older adults (OA). METHODS:Twenty YA (27.2 ± 2.7 years) and twenty OA (65.3 ± 9.5 years) underwent iTBS-γ tACS and iTBS-sham tACS in randomized sessions. In a separate session, we delivered γ-tACS alone and recorded SICI during stimulation. RESULTS:iTBS-sham tACS produced comparable motor evoked potential (MEP) facilitation between groups. While iTBS-γ tACS boosted MEP facilitation in both the YA and OA groups, the magnitude of its effect was significantly lower in OA. Similarly, γ-tACS-induced modulation of GABA-A-ergic neurotransmission, as tested by SICI, was reduced in OA. The effect of iTBS-γ tACS negatively correlated with the age of OA subjects. CONCLUSIONS: Mechanisms underlying the effects of γ oscillations on LTP-like plasticity become less efficient in older adults. This could reflect age-related changes in neural elements of M1 resonant to γ oscillations, including GABA-A-ergic interneurons. SIGNIFICANCE: The beneficial effect of γ-tACS on iTBS-induced plasticity is reduced in older adults.
RCT Entities:
OBJECTIVE: In healthy subjects, the long-term potentiation (LTP)-like plasticity of the primary motor cortex (M1) induced by intermittent theta-burst stimulation (iTBS) can be boosted by modulating gamma (γ) oscillations through transcranial alternating current stimulation (tACS). γ-tACS also reduces short-interval intracortical inhibition (SICI). We tested whether the effects of γ-tACS differ between young (YA) and older adults (OA). METHODS: Twenty YA (27.2 ± 2.7 years) and twenty OA (65.3 ± 9.5 years) underwent iTBS-γ tACS and iTBS-sham tACS in randomized sessions. In a separate session, we delivered γ-tACS alone and recorded SICI during stimulation. RESULTS:iTBS-sham tACS produced comparable motor evoked potential (MEP) facilitation between groups. While iTBS-γ tACS boosted MEP facilitation in both the YA and OA groups, the magnitude of its effect was significantly lower in OA. Similarly, γ-tACS-induced modulation of GABA-A-ergic neurotransmission, as tested by SICI, was reduced in OA. The effect of iTBS-γ tACS negatively correlated with the age of OA subjects. CONCLUSIONS: Mechanisms underlying the effects of γ oscillations on LTP-like plasticity become less efficient in older adults. This could reflect age-related changes in neural elements of M1 resonant to γ oscillations, including GABA-A-ergic interneurons. SIGNIFICANCE: The beneficial effect of γ-tACS on iTBS-induced plasticity is reduced in older adults.
Authors: Christopher L Groth; Arun Singh; Qiang Zhang; Brian D Berman; Nandakumar S Narayanan Journal: Tremor Other Hyperkinet Mov (N Y) Date: 2021-11-10
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