Mouchnino Laurence, Fontan Aurélie, Tandonnet Christophe, Perrier Joy, Saradjian Anahid H, Blouin Jean, Simoneau Martin
Aix-Marseille Université, CNRS, Laboratoire de Neurosciences Cognitives, FR 3C, Marseille, France;
Aix-Marseille Université, CNRS, Laboratoire de Psychologie Cognitive, Marseille, France;
J Neurophysiol. 2015 Jul;114(1):301-8. doi: 10.1152/jn.00668.2014. Epub 2015 Apr 29.
It has been shown that during the planning of a voluntary movement the transmission of cutaneous afferent inputs to the somatosensory cortex is attenuated shortly before the motor output as well as during movement execution. However, it is not known whether the sensory suppression observed during the planning phase (i.e., before any movement execution) is a systemic phenomenon or whether it is dependent on movement context. For example, movements such as step initiation are controlled based on information received from cutaneous receptors in the feet. Because afferent information emerging from these receptors is critical for movement initiation, we hypothesized that suppression of these inputs may not occur during the planning phase prior to gait initiation. To examine this hypothesis we measured the cortical response to somatosensory stimulation during the planning phase of step initiation and during movement execution. Sensitivity to cutaneous stimulation was assessed by measuring the amplitude of the cortical somatosensory-evoked potential (SEP, over the Cz electrode) following electrical stimulations of the plantar sole of one foot. Two stimulations were provided during the planning phase of a step movement and two stimulations during movement execution. It was found that the P50-N80 SEP was facilitated in the early planning phase (-700 ms before motor execution) compared with when participants remained still (control standing task). This mechanism might contribute to an enhanced perception of cutaneous input leading to a more accurate setting of the forces to be exerted onto the ground to shift the body's weight toward the supporting side prior to foot-off.
研究表明，在自主运动的计划阶段，皮肤传入输入向体感皮层的传递在运动输出前不久以及运动执行期间会减弱。然而，尚不清楚在计划阶段（即在任何运动执行之前）观察到的感觉抑制是一种全身性现象，还是取决于运动背景。例如，诸如起步等动作是基于从足部皮肤感受器接收到的信息来控制的。由于这些感受器产生的传入信息对于动作启动至关重要，我们推测在步态启动前的计划阶段可能不会发生对这些输入的抑制。为了检验这一假设，我们在起步的计划阶段和运动执行期间测量了对体感刺激的皮层反应。通过测量在一只脚底进行电刺激后皮层体感诱发电位（SEP，在Cz电极上方）的幅度来评估对皮肤刺激的敏感性。在一个步行动作的计划阶段提供两次刺激，在运动执行期间提供两次刺激。结果发现，与参与者静止不动时（对照站立任务）相比，在早期计划阶段（运动执行前700毫秒）P50 - N80 SEP得到了促进。这种机制可能有助于增强对皮肤输入的感知，从而在离地前更准确地设定施加在地面上的力，以便将身体重量转移到支撑侧。
