Journal article
Evidence for high-fidelity timing-dependent synaptic plasticity of human motor cortex
Journal of Neurophysiology, Vol.109(1), pp.106-112
2013
Abstract
A single transcranial magnetic stimulation (TMS) pulse typically evokes a short series of spikes in corticospinal neurons [known as indirect (I)-waves] which are thought to arise from transynaptic input. Delivering a second pulse at inter-pulse intervals (IPIs) corresponding to the timing of these I-waves leads to a facilitation of the response, and if stimulus pairs are delivered repeatedly, a persistent LTP-like increase in excitability can occur. This has been demonstrated at an IPI of 1.5 ms, which corresponds to the first I-wave interval, in an intervention referred to as ITMS (I-wave TMS), and it has been argued that this may have similarities with timing-dependent plasticity models. Consequently, we hypothesized that if the second stimulus is delivered so as not to coincide with I-wave timing, it should lead to LTD. We performed a crossover study in 10 subjects in which TMS doublets were timed to coincide (1.5-ms IPI, ITMS1.5) or not coincide (2-ms IPI, ITMS2) with I-wave firing. Single pulse motor-evoked potential (MEP) amplitude, resting motor threshold (RMT), and short-interval cortical inhibition (SICI) were measured from the first dorsal interosseous (FDI) muscle. After ITMS1.5 corticomotor excitability was increased by ∼60% for 15 min (P < 0.05) and returned to baseline by 20 min. Increasing the IPI by just 500 μs to 2 ms reversed the aftereffect, and MEP amplitude was significantly reduced (∼35%, P < 0.05) for 15 min before returning to baseline. This reduction was not associated with an increase in SICI, suggesting a reduction in excitatory transmission rather than an increase in inhibitory efficacy. RMT also remained unchanged, suggesting that these changes were not due to changes in membrane excitability. Amplitude-matching ITMS2 did not modulate excitability. The results are consistent with timing-dependent synaptic LTP/D-like effects and suggest that there are plasticity mechanisms operating in the human motor cortex with a temporal resolution of the order of a few hundreds of microseconds.
Details
- Title
- Evidence for high-fidelity timing-dependent synaptic plasticity of human motor cortex
- Authors/Creators
- R.F.H. Cash (Author/Creator) - Perron Institute for Neurological and Translational ScienceF.L. Mastaglia (Author/Creator) - Perron Institute for Neurological and Translational ScienceG. W. Thickbroom (Author/Creator) - Perron Institute for Neurological and Translational Science
- Publication Details
- Journal of Neurophysiology, Vol.109(1), pp.106-112
- Publisher
- American Physiological Society
- Identifiers
- 991005544912507891
- Murdoch Affiliation
- Murdoch University
- Language
- English
- Resource Type
- Journal article
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- Citation topics
- 1 Clinical & Life Sciences
- 1.82 Gait & Posture
- 1.82.811 Transcranial Magnetic Stimulation
- Web Of Science research areas
- Neurosciences
- Physiology
- ESI research areas
- Neuroscience & Behavior