The effect of gamma oscillations in boosting primary motor cortex plasticity is greater in young than older adults. Issue 6 (June 2021)

• Record Type: Journal Article
• Authors: Guerra, Andrea; Asci, Francesco; Zampogna, Alessandro; D'Onofrio, Valentina; Berardelli, Alfredo; Suppa, Antonio
• Is Part Of: Clinical neurophysiology. Volume 132:Issue 6(2021)
• Page Start: 1358
• Page End: 1366
• Publication Date: 2021-06
• Subjects: Gamma oscillations -- Aging -- Plasticity -- Motor cortex -- tACS -- Theta-burst stimulation; Neurophysiology -- Periodicals; Electroencephalography -- Periodicals; Electromyography -- Periodicals; Neurology -- Periodicals; 612.8
• DOI: 10.1016/j.clinph.2021.01.032
• Languages: English
• ISSNs: 1388-2457

Abstract

Highlights: Gamma-transcranial alternating current stimulation (γ-tACS) boosted the iTBS-induced plasticity in both young and older adults. The effects of iTBS-γ tACS as well as of γ-tACS alone were significantly weaker in older than young adults. The effects of iTBS-γ tACS negatively correlated with the age of older adults. 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.