BACKGROUND Neural information processing is subject to noise and this leads to variability in neural firing and behavior. Schizophrenia has been associated with both more variable motor control and impaired cortical inhibition, which is crucial for excitatory/inhibitory balance in neural commands. HYPOTHESIS In this study, we hypothesized that impaired intracortical inhibition in motor cortex would contribute to task-related motor noise in schizophrenia. METHODS We measured variability of force and of electromyographic (EMG) activity in upper limb and hand muscles during a visuomotor grip force-tracking paradigm in patients with schizophrenia (N=25), in unaffected siblings (N=17) and in healthy control participants (N=25). Task-dependent primary motor cortex (M1) excitability and inhibition were assessed using transcranial magnetic stimulation (TMS). RESULTS During force maintenance patients with schizophrenia showed increased variability in force and EMG, despite similar mean force and EMG magnitudes. Compared to healthy controls, patients with schizophrenia also showed increased M1 excitability and reduced cortical inhibition during grip-force tracking. EMG variability and force variability correlated negatively to cortical inhibition in patients with schizophrenia. EMG variability also correlated positively to negative symptoms. Siblings had similar variability and cortical inhibition compared to controls. Increased EMG and force variability indicate enhanced motor noise in schizophrenia, which relates to reduced motor cortex inhibition. CONCLUSION The findings suggest that excessive motor noise in schizophrenia may arise from an imbalance of M1 excitation/inhibition of GABAergic origin. Thus, higher motor noise may provide a useful marker of impaired cortical inhibition in schizophrenia.

中文翻译：

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精神分裂症的神经噪声和皮质抑制

背景技术神经信息处理易受噪声影响，这会导致神经放电和行为的可变性。精神分裂症与更可变的运动控制和受损的皮质抑制有关，这对于神经命令的兴奋/抑制平衡至关重要。假设在这项研究中，我们假设运动皮层皮质内抑制受损会导致精神分裂症中与任务相关的运动噪音。方法 我们测量了精神分裂症患者 (N=25)、未受影响的兄弟姐妹 (N=17) 和健康对照参与者在视觉运动握力追踪范式期间上肢和手部肌肉的力量和肌电图 (EMG) 活动的变异性(N=25)。使用经颅磁刺激 (TMS) 评估依赖于任务的初级运动皮层 (M1) 的兴奋性和抑制性。结果 在力量维持期间，精神分裂症患者表现出力量和 EMG 的变异性增加，尽管平均力量和 EMG 幅度相似。与健康对照相比，精神分裂症患者在握力追踪过程中还表现出 M1 兴奋性增加和皮质抑制减少。EMG 变异性和力变异性与精神分裂症患者的皮质抑制呈负相关。EMG 变异性也与阴性症状呈正相关。与对照组相比，兄弟姐妹具有相似的变异性和皮质抑制。EMG 和力量变异性增加表明精神分裂症中运动噪音增强，这与运动皮层抑制减少有关。结论 研究结果表明，精神分裂症患者的过度运动噪音可能是由 GABA 能源的 M1 兴奋/抑制失衡引起的。因此，较高的运动噪音可能是精神分裂症患者皮质抑制受损的有用标志。