Palmer Jacqueline A, Halter Alice, Gray Whitney, Wolf Steven L, Borich Michael R
Department of Rehabilitation Medicine, Division of Physical Therapy, Emory University, Atlanta, GA, United States.
Atlanta VA Health Care System Visual and Neurocognitive Center of Excellence, Decatur, GA, United States.
Front Hum Neurosci. 2019 Jan 29;13:8. doi: 10.3389/fnhum.2019.00008. eCollection 2019.
Repeated pairing of electrical stimulation of a peripheral nerve with transcranial magnetic stimulation (TMS) over the primary motor cortex (M1) representation for a target muscle can induce neuroplastic adaptations in the human brain related to motor learning. The extent to which the motor state during this form of paired associative stimulation (PAS) influences the degree and mechanisms of neuroplasticity or motor learning is unclear. Here, we investigated the effect of volitional muscle contraction during PAS on: (1) measures of general corticomotor excitability and intracortical circuit excitability; and (2) motor performance and learning. We assessed measures of corticomotor excitability using TMS and motor skill performance during a serial reaction time task (SRTT) at baseline and at 0, 30, 60 min post-PAS. Participants completed a SRTT retention test 1 week following the first two PAS sessions. Following the PAS intervention where the hand muscle maintained an active muscle contraction (PAS), there was lower short interval intracortical inhibition compared to PAS during a resting motor state (PAS) and a sham PAS condition (PAS). SRTT performance improved within the session regardless of PAS condition. SRTT retention was greater following both PAS and PAS after 1 week compared to PAS. These findings suggest that PAS may enhance motor learning retention and that motor state may be used to target different neural mechanisms of intracortical excitation and inhibition during PAS. This observation may be important to consider for the use of therapeutic noninvasive brain stimulation in neurologic patient populations.
将外周神经的电刺激与经颅磁刺激（TMS）在初级运动皮层（M1）对目标肌肉的表征上进行重复配对，可在人脑中诱导与运动学习相关的神经可塑性适应。在这种形式的配对联想刺激（PAS）过程中，运动状态对外周神经可塑性或运动学习的程度和机制的影响尚不清楚。在这里，我们研究了PAS期间自主肌肉收缩对以下方面的影响：（1）一般皮质运动兴奋性和皮质内回路兴奋性的测量；（2）运动表现和学习。我们在基线以及PAS后0、30、60分钟时，使用TMS评估皮质运动兴奋性测量指标，并在序列反应时任务（SRTT）中评估运动技能表现。在前两次PAS训练后的1周，参与者完成了SRTT保留测试。在PAS干预中，手部肌肉保持主动肌肉收缩（PAS），与静息运动状态下的PAS（PAS）和假PAS条件（PAS）相比，短间隔皮质内抑制较低。无论PAS条件如何，SRTT表现在训练期间均有所改善。与PAS相比，PAS和PAS后1周的SRTT保留率更高。这些发现表明，PAS可能会增强运动学习保留率，并且运动状态可用于在PAS期间针对皮质内兴奋和抑制的不同神经机制。对于在神经疾病患者群体中使用治疗性非侵入性脑刺激而言，这一观察结果可能具有重要意义。
