Effect of Physiological Activity on an NMDA-Dependent Form of Cortical Plasticity in Human

Abstract

Retention of motor learning can be enhanced or degraded by subsequent performance of a different task. Neurophysiologically this may reflect interference in synaptic plasticity by ongoing neural activity in the brain. Here we demonstrate that N-methyl-D-aspartate (NMDA) dependent aftereffects of repetitive transcranial magnetic stimulation (rTMS) also are subject to interference effects, suggesting that it may be possible to investigate these basic mechanisms in the intact human brain. We measured the motor-evoked potential (MEP) amplitude and short-interval intracortical inhibition (SICI) in the first dorsal interosseous (FDI) muscle after continuous or intermittent theta burst (cTBS/iTBS) forms of rTMS. In resting subjects, cTBS depressed MEPs and reduced SICI for about 20 min, whereas iTBS had the opposite effect. However, if subjects contracted the FDI during TBS, then effects on the MEP were abolished, although effects of cTBS on SICI remained. Contraction immediately after TBS enhanced the facilitatory effect of iTBS and reversed the usual inhibitory effect of cTBS into facilitation. Contraction 10 min after cTBS (iTBS not tested) had only a transient (3-4 min) effect on MEPs. These interactions with behavior may relate to mechanisms of interference between learning paradigms in human and be similar to effects on synaptic long-term potentiation/depression described in animal experiments.

Abnormal Mechanisms of Plasticity and Metaplasticity in Autism Spectrum Disorders and Fragile X Syndrome

“…cTBS was applied according to the standard protocol that was consistent with our previous studies in ASD and FXS (i.e., three pulses of 50-Hz rTMS repeated every 200 ms for a total of 40 seconds [for a total of 600 pulses]) at an intensity of 80% of AMT (Huang et al 2005(Huang et al , 2008Oberman et al 2010Oberman et al , 2012Oberman et al , 2015. Corticospinal excitability was assessed both before and after cTBS by measuring peak-to-peak amplitude of MEPs induced in the contralateral first dorsal interosseus (FDI) muscle in response to supra threshold (120% of resting motor threshold [RMT] intensity) single-pulse TMS.…”

“…cTBS was specifically developed to probe plasticity mechanisms (Huang et al 2005(Huang et al , 2007Cardenas-Morales et al 2010) and involves application of three pulses of 50-Hz rTMS repeated every 200 ms for a total of 40 seconds (for total of 600 pulses) at an intensity of 80% of the active motor threshold (AMT) (Huang et al 2005(Huang et al , 2008. After cTBS is applied to the motor cortex, TMS-induced MEPs typically show decreased amplitude for a period of 20-30 minutes in healthy adult brains.…”

Probing changes in corticospinal excitability following theta burst stimulation of the human primary motor cortex

“…1). EMG activity was monitored at all times post-TBS in both experiments to ensure complete relaxation of the right FDI and minimise the influence of voluntary contraction on the TBS response (Goldsworthy et al, 2014b;Huang et al, 2008).…”

Response-Dependent Contributions of Human Primary Motor Cortex and Angular Gyrus to Manual and Perceptual Sequence Learning

“…We used the cTBS protocol because it induces disruption that outlasts the time of stimulation (up to 60 min) and the effects are mediated by an analog of the type of long-term potentiation-and/or long-term depression-like changes in synaptic transmission that have been implicated in learning and memory (Ziemann et al, 2004;Huang et al, 2005Huang et al, , 2008Cheeran et al, 2008). Responses on the SRT task involved either sequential unimanual key presses and free eye movements (experiment 1; manual condition) or covert reorienting of visuospatial attention (experiment 2; perceptual condition).…”