Laboratoire de Neurosciences Cognitives, Fédération de Recherche Comportement-Cerveau-Cognition, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France; Department of Neurology and Movement Disorders, Aix-Marseille Université, Pôle de Neurosciences Cliniques, Assistance Publique-Hôpitaux de Marseille, La Timone, 13385 Marseille cedex 05, France.
Laboratoire de Neurosciences Cognitives, Fédération de Recherche Comportement-Cerveau-Cognition, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France.
Neuropsychologia. 2018 Aug;117:167-177. doi: 10.1016/j.neuropsychologia.2018.02.016. Epub 2018 Feb 16.
Deep brain stimulation of the subthalamic nucleus (STN DBS) is known to increase response speed and lower response accuracy in Parkinson's disease (PD) patients. It has been proposed that this speed-accuracy tradeoff is due to enhanced sensitivity of the motor system to sensory information. An alternative possibility is that this effect is due to weakened suppressive processes. The two alternative interpretations can be tested by analyzing the electromyographic activity (EMG) of the response agonists when the patients perform conflict reaction time tasks. In those tasks, fast subthreshold muscle impulses often occur in the agonist of the incorrect response. These impulses are partial errors that are suppressed before being behaviourally committed.
Here we analyzed the EMG of the response agonists recorded while sixteen PD patients performed a Simon task that elicits prepotent response tendencies so as to decipher (i) whether STN DBS affects the expression and/or suppression of subthreshold muscle impulses that are critical for action control and (ii) the interaction between dopaminergic treatment and STN DBS. The patients were tested On and Off STN DBS and On and Off dopaminergic medication in a full factorial design.
STN DBS not only impaired the proficiency to suppress subliminal action impulses (p = 0.01) but also favoured the muscular expression of fast incorrect impulses (p < 0.001). Dopaminergic treatment only affected the action impulses suppression (p = 0.02) and did not change the effect of STN DBS on impulsive action control.
Contrary to a recent proposal, STN DBS impaired rather than improved action control by weakening erroneous impulse suppression, whether the patients were On or Off their usual medication. These findings are discussed in light of a recent proposal (Servant M, White C, Montagnini A, Burle B, 2015) that reconciles partial errors with accumulation-to-bound models of decision making. Our results suggest that medication specifically lowers the mechanical threshold while STN DBS lowers the mechanical threshold and to a lesser extent the EMG-threshold.
已知丘脑底核（STN）深部脑刺激（DBS）可增加帕金森病（PD）患者的反应速度并降低反应准确性。有人提出，这种速度-准确性权衡是由于运动系统对感觉信息的敏感性增强所致。另一种可能性是，这种影响是由于抑制过程减弱所致。可以通过分析患者执行冲突反应时任务时的反应激动剂的肌电图（EMG）来测试这两种替代解释。在这些任务中，快速的亚阈值肌肉冲动经常出现在错误反应的激动剂中。这些冲动是部分错误，在行为上做出承诺之前被抑制。
在这里，我们分析了 16 名 PD 患者在执行 Simon 任务时记录的反应激动剂的 EMG，该任务引发了强烈的反应倾向，以便（i）确定 STN DBS 是否影响动作控制关键的亚阈值肌肉冲动的表达和/或抑制，以及（ii）多巴胺能治疗和 STN DBS 之间的相互作用。患者在 STN DBS 开启和关闭以及多巴胺能药物开启和关闭的情况下，以完全因子设计进行测试。
STN DBS 不仅损害了抑制潜意识动作冲动的熟练程度（p=0.01），而且还促进了快速错误冲动的肌肉表达（p<0.001）。多巴胺能治疗仅影响动作冲动的抑制（p=0.02），并且不会改变 STN DBS 对冲动动作控制的影响。
与最近的一项提议相反，无论患者是否服用常规药物，STN DBS 通过削弱错误冲动的抑制而不是改善动作控制。这些发现与最近的一项提议（Servant M、White C、Montagnini A、Burle B，2015）相协调，该提议将部分错误与决策的累积到边界模型相协调。我们的结果表明，药物专门降低机械阈值，而 STN DBS 降低机械阈值并在较小程度上降低 EMG 阈值。
