title: The effect of age on the homotopic motor cortical long-term potentiation-like effect induced by quadripulse stimulation.
abstract: The reduction of plasticity with age has been shown by many previous papers in animal experiments. This issue can be studied in humans because several non-invasive brain stimulation techniques induce synaptic plasticity in the human brain. We investigated the influence of individuals' age on the responder rate of the long-term potentiation (LTP)-like effect induced by quadripulse magnetic stimulation (QPS). The participants were 107 healthy volunteers: 53 older participants (Mean ± SD 65.0 ± 1.5 years) and 54 younger participants (37.2 ± 8.7). The quadripulse stimulation with 5-ms inter-pulse interval (QPS5) was applied over the primary motor cortex (M1). We measured motor evoked potentials (MEPs) before QPS, and at five time points after QPS for up to 25 min. In each participant, average MEP amplitude (size) ratios were quantified. We first classified participants as responders and non-responders simply by comparing the size ratio with 1.0 for consistency with previous studies, then as "significant responders", "non-responders", and "opposite responders" for more detailed analysis by comparing the size ratio with the mean and standard deviation of the MEP size ratios of the sham condition. The degree of LTP-like effects induced by QPS5 was significantly smaller in the older group compared to the younger group. Also, the rates of responders and significant responders were lower in the older group (58 and 47%, respectively) compared to the younger group (80 and 76%, respectively). The age of the participants significantly affected the LTP-like effect induced by QPS5, which suggests that brain plasticity decreases with age.
authors.affiliation: Department of Neurology, Kitasato University School of Medicine, 2-1-1 Asamizodai, Minami-ku, Sagamihara, Kanagawa, 252-0380, Japan. hanajima-tky@umin.ac.jp.|Department of Neurology, The University of Tokyo, Tokyo, Japan. hanajima-tky@umin.ac.jp.|Division of Neurology, Department of Brain and Neurosciences, Faculty of Medicine, Tottori University, Yonago, Japan. hanajima-tky@umin.ac.jp.
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Hanajima
authors.affiliation: Department of Neurology, The University of Tokyo, Tokyo, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Tanaka
authors.affiliation: Department of Neurology, Kitasato University School of Medicine, 2-1-1 Asamizodai, Minami-ku, Sagamihara, Kanagawa, 252-0380, Japan.|Department of Neurology, The University of Tokyo, Tokyo, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Tsutsumi
authors.affiliation: Department of Neurology, Fukushima Medical University, Fukushima, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Enomoto
authors.affiliation: Department of Neurology, Fukushima Medical University, Fukushima, Japan.
authors.forename: Mitsunari
authors.initials: M
authors.lastname: Abe
authors.affiliation: Department of Neurology, Fukushima Medical University, Fukushima, Japan.
authors.forename: Koichiro
authors.initials: K
authors.lastname: Nakamura
authors.affiliation: Department of Neurology, Fukushima Medical University, Fukushima, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Kobayashi
authors.affiliation: Department of Neurology, The University of Tokyo, Tokyo, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Hamada
authors.affiliation: Department of Neurology, Kitasato University School of Medicine, 2-1-1 Asamizodai, Minami-ku, Sagamihara, Kanagawa, 252-0380, Japan.|Department of Neurology, The University of Tokyo, Tokyo, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Shimizu
authors.affiliation: Department of Neurology, The University of Tokyo, Tokyo, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Terao
authors.affiliation: Department of Neurology, Fukushima Medical University, Fukushima, Japan.|Advanced Clinical Research Center, Fukushima Global Medical Science Center, Fukushima Medical University, Fukushima, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Ugawa
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D017774:Long-Term Potentiation / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D011601:Psychophysics; D050781:Transcranial Magnetic Stimulation
keywords: Age dependence; Cortical plasticity; Transcranial magnetic stimulation; Variability