Key pointsr Ischaemic nerve block (INB) of the forearm rapidly reduces somatosensory input to a part of the body, which leads to the functional reorganization of the temporarily deafferented primary motor cortex (M1).r We applied a novel modified INB (mINB) to the forearm, maintaining mean blood pressure, to assess cortical plasticity in the primary somatosensory cortex (S1) and the M1 regions associated with small hand muscles. r S1 excitability was measured by median nerve somatosensory-evoked potentials (SEPs), while M1 excitability was evaluated by motor-evoked potentials (MEPS), using transcranial magnetic stimulation.r The finding that S1 excitability increased and M1 excitability decreased after the mINB was removed reflects the differential short-term cortical plasticity of the S1 and M1 regions.r These opposite effects observed for the S1 and M1 regions following the mINB may indicate a possible intra-hemispheric interaction between the S1 and M1 regions.Abstract Ischaemic nerve block (INB) causes short-term sensory deprivation, leading to functional reorganization in the deafferented motor cortex (M1). We used a modified INB (mINB) to evaluate cortical plasticity in the somatosensory cortex (S1) and M1 region associated with small hand muscles, because INB strongly inhibits muscles distal to the tourniquet. Thirty-three healthy adults participated in different combinations of four experiments. A pneumatic tourniquet was placed just below the right elbow and inflated to induce a mINB. We recorded the median nerve somatosensory-and motor-evoked potentials (SEPs and MEPs) before, during and after mINB placement and assessed spinal cord excitability using F-wave measurements. SEPs at Erb's point (N9) were abolished during the mINB; those at cortical N20 were suppressed. After removing the mINB, N20 amplitudes increased significantly, while those at N9 did not fully recover. P14 amplitudes after tourniquet deflation immediately recovered to baseline levels. M1-MEP amplitudes decreased during the mINB, and Erb-MEPs were suppressed. After the mINB was Ryutaro Hayashi is a PhD candidate at Kyushu University. He uses modified ischaemic nerve block (mINB) of the forearm to investigate plastic changes in the primary sensory (S1) and motor (M1) cortices. He found that mINB enhanced S1 excitability and reduced M1 excitability. This method could be useful for developing new neuromodulation protocols. His primary research focuses on understanding cortical plasticity that is induced by transcranial magnetic stimulation or transcranial alternating current stimulation, with the aim of improving our understanding of M1 function in humans. J Physiol 597.13 removed, M1-MEPs remained suppressed, while Erb-MEPs fully recovered. F-waves were not affected by the intervention. Therefore, sensory, but not motor, nerve function was affected by the mINB. S1 excitability was enhanced after the mINB was removed, indicating that S1 and M1 excitability were modulated in opposing directions after deflation. These after-effects may re...
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