McNickle Emmet, Carson Richard G
Trinity College Institute of Neuroscience and School of Psychology, Trinity College Dublin, Ireland; School of Psychology, Queen's University Belfast, Northern Ireland, UK.
J Physiol. 2015 Apr 1;593(7):1649-66. doi: 10.1113/jphysiol.2014.280453. Epub 2015 Jan 12.
Many types of non-invasive brain stimulation alter corticospinal excitability (CSE). Paired associative stimulation (PAS) has attracted particular attention as its effects ostensibly adhere to Hebbian principles of neural plasticity. In prototypical form, a single electrical stimulus is directed to a peripheral nerve in close temporal contiguity with transcranial magnetic stimulation delivered to the contralateral primary motor cortex (M1). Repeated pairing of the two discrete stimulus events (i.e. association) over an extended period either increases or decreases the excitability of corticospinal projections from M1, contingent on the interstimulus interval. We studied a novel form of associative stimulation, consisting of brief trains of peripheral afferent stimulation paired with short bursts of high frequency (≥80 Hz) transcranial alternating current stimulation (tACS) over contralateral M1. Elevations in the excitability of corticospinal projections to the forearm were observed for a range of tACS frequency (80, 140 and 250 Hz), current (1, 2 and 3 mA) and duration (500 and 1000 ms) parameters. The effects were at least as reliable as those brought about by PAS or transcranial direct current stimulation. When paired with tACS, muscle tendon vibration also induced elevations of CSE. No such changes were brought about by the tACS or peripheral afferent stimulation alone. In demonstrating that associative effects are expressed when the timing of the peripheral and cortical events is not precisely circumscribed, these findings suggest that multiple cellular pathways may contribute to a long term potentiation-type response. Their relative contributions will differ depending on the nature of the induction protocol that is used.
多种非侵入性脑刺激可改变皮质脊髓兴奋性（CSE）。配对联想刺激（PAS）因其效应表面上遵循神经可塑性的赫布原理而备受关注。典型形式是，将单个电刺激施加到外周神经，同时将经颅磁刺激施加到对侧初级运动皮层（M1），二者在时间上紧密相邻。在较长时间内重复这两个离散刺激事件（即联想），根据刺激间隔的不同，可增加或降低M1皮质脊髓投射的兴奋性。我们研究了一种新型联想刺激形式，即由短暂的外周传入刺激序列与对侧M1上的高频（≥80 Hz）经颅交流电刺激（tACS）短脉冲配对组成。在一系列tACS频率（80、140和250 Hz）、电流（1、2和3 mA）和持续时间（500和1000 ms）参数下，观察到皮质脊髓向前臂投射的兴奋性升高。这些效应至少与PAS或经颅直流电刺激所产生的效应一样可靠。当与tACS配对时，肌腱振动也会引起CSE升高。单独的tACS或外周传入刺激不会产生这种变化。这些发现表明，当外周和皮质事件的时间没有精确限定也能表现出联想效应，这表明多种细胞通路可能促成了长时程增强型反应。它们的相对贡献将因所采用的诱导方案的性质而异。
