University of Miami, Department of Neurological Surgery, The Miami Project to Cure Paralysis, Miami, Florida 33136, and Bruce W. Carter Department of Veterans Affairs Medical Center, Miami, Florida 33125.
University of Miami, Department of Neurological Surgery, The Miami Project to Cure Paralysis, Miami, Florida 33136, and Bruce W. Carter Department of Veterans Affairs Medical Center, Miami, Florida 33125
J Neurosci. 2018 Aug 15;38(33):7237-7247. doi: 10.1523/JNEUROSCI.0545-18.2018. Epub 2018 Jul 5.
Afferent input from the periphery to the cortex contributes to the control of grasping. How sensory input is gated along the ascending sensory pathway and its functional role during gross and fine grasping in humans remain largely unknown. To address this question, we assessed somatosensory-evoked potential components reflecting activation at subcortical and cortical levels and psychophysical tests at rest, during index finger abduction, precision, and power grip. We found that sensory gating at subcortical level and in the primary somatosensory cortex (S1), as well as intracortical inhibition in the S1, increased during power grip compared with the other tasks. To probe the functional relevance of gating in the S1, we examined somatosensory temporal discrimination threshold by measuring the shortest time interval to perceive a pair of electrical stimuli. Somatosensory temporal discrimination threshold increased during power grip, and higher threshold was associated with increased intracortical inhibition in the S1. These novel findings indicate that humans gate sensory input at subcortical level and in the S1 largely during gross compared with fine grasping. Inhibitory processes in the S1 may increase discrimination threshold to allow better performance during power grip. Most of our daily life actions involve grasping. Here, we demonstrate that gating of afferent input increases at subcortical level and in the primary somatosensory cortex (S1) during gross compared with fine grasping in intact humans. The precise timing of sensory information is critical for human perception and behavior. Notably, we found that the ability to perceive a pair of electrical stimuli, as measured by the somatosensory temporal discrimination threshold, increased during power grip compared with the other tasks. We propose that reduced afferent input to the S1 during gross grasping behaviors diminishes temporal discrimination of sensory processes related, at least in part, to increased inhibitory processes within the S1.
感觉传入从外周向皮层的输入有助于抓握的控制。感觉输入如何沿着上升的感觉通路进行门控，以及它在人类的粗抓和细抓中的功能作用在很大程度上仍然未知。为了解决这个问题，我们评估了反映亚皮质和皮质水平激活的体感诱发电位成分，以及在休息时、食指外展时、精细抓握时和力量抓握时的心理物理测试。我们发现，与其他任务相比，力量抓握时，亚皮质水平和初级体感皮层（S1）的感觉门控以及 S1 中的皮质内抑制增加。为了探究 S1 中的门控的功能相关性，我们通过测量感知一对电刺激的最短时间间隔来检查体感时间辨别阈值。在力量抓握时，体感时间辨别阈值增加，而较高的阈值与 S1 中的皮质内抑制增加相关。这些新发现表明，与精细抓握相比，人类在粗抓时主要在亚皮质水平和 S1 中对感觉输入进行门控。S1 中的抑制过程可能会增加辨别阈值，以在力量抓握时获得更好的性能。我们日常生活中的大多数动作都涉及抓握。在这里，我们证明在完整的人类中，与精细抓握相比，在粗抓时，感觉传入在亚皮质水平和初级体感皮层（S1）中的门控增加。感觉信息的精确时间对人类感知和行为至关重要。值得注意的是，我们发现与其他任务相比，力量抓握时，体感时间辨别阈值增加，这表明感知一对电刺激的能力增加。我们提出，在粗抓行为期间，传入 S1 的感觉输入减少，至少部分地与 S1 内增加的抑制过程相关，降低了与感觉过程相关的时间辨别能力。
