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初级体感皮层在听觉节奏性手指敲击任务中的作用。

The role of the primary somatosensory cortex in an auditorily paced finger tapping task.

作者信息

Pollok Bettina, Müller Katharina, Aschersleben Gisa, Schnitzler Alfons, Prinz Wolfgang

机构信息

Department of Neurology, Heinrich-Heine University, Düsseldorf, Germany.

出版信息

Exp Brain Res. 2004 May;156(1):111-7. doi: 10.1007/s00221-004-1879-0. Epub 2004 Mar 9.

Abstract

It has been suggested that a simple auditorily paced finger tapping task is associated with three tap-related neuromagnetic sources in the primary sensorimotor cortex contralateral to the tapping hand. Since a first source peaking at approximately 100 ms before tap-onset most likely represents activation of the primary motor cortex (M1) due to the motor command, a second source localized in the primary somatosensory cortex (S1) peaking around tap-onset could be due to kinesthetic feedback of the finger movement. A third source peaking at approximately 100 ms after tap-onset is also localized in the primary somatosensory cortex but inferior to the first S1 source (S1 inferior). The functional meaning of this source is still under debate. On the one hand it has been argued that S1 inferior represents the neuromagnetic correlate of tactile-kinesthetic feedback due to finger-taps and movements. On the other hand the functional meaning of this source could go beyond the sole processing of somatosensory feedback monitoring the temporal distance between tap and pacer (click) to keep the subject in time with the external event. This hypothesis is based on the observation that (1). S1 inferior seems to be coupled equally well to tap and click and (2). that this source might be triggered by the last event (i.e. tap or click). In the present study we re-examined this hypothesis by using a 122-channel whole-head neuromagnetometer. Eight healthy subjects synchronized their right index finger taps to an auditory pacing signal presented with a constant interstimulus interval of 800 ms. To test the hypothesis that the last event triggers S1 inferior we compared neuromagnetic activity following the tap as the first and the last event. In the auditorily paced finger tapping task usually the tap leads over the click (negative asynchrony). Therefore, the tap usually occurs as the first event. Since it has been shown that delivering additional feedback at the time of tap-onset results in a reduced negative asynchrony, in a second run auditory feedback was presented at tap-onset to enhance the number of positive asynchronies (i.e. the tap is the last event). Since no latency differences of S1 inferior associated with positive and negative asynchronies were found, results from the present study do not support the assumption that S1 inferior is triggered by the last event. Moreover, the amplitude of S1 inferior is significantly reduced following positive asynchronies as compared to negative asynchronies. Additionally, tap duration (i.e. the time between tap-onset and tap-offset) is significantly reduced while subjects produce positive asynchronies. Therefore, the amplitude of S1 inferior seems to be modulated by movement kinematics. This observation agrees well with the idea that activation of S1 is solely associated with the processing of somatosensory information. To conclude, our data contradict the hypothesis of an evaluation process localized in the primary somatosensory cortex and substantiate the idea that S1 inferior exclusively represents the processing of somatosensory feedback information.

摘要

有人提出,一个简单的听觉节奏手指敲击任务与敲击手对侧的初级感觉运动皮层中三个与敲击相关的神经磁源有关。由于第一个在敲击开始前约100毫秒达到峰值的源很可能代表由于运动指令而引起的初级运动皮层(M1)的激活,那么位于初级体感皮层(S1)且在敲击开始时左右达到峰值的第二个源可能是由于手指运动的动觉反馈。第三个在敲击开始后约100毫秒达到峰值的源也位于初级体感皮层,但在第一个S1源(S1下)的下方。这个源的功能意义仍在争论中。一方面,有人认为S1下代表由于手指敲击和运动而产生的触觉 - 动觉反馈的神经磁相关物。另一方面,这个源的功能意义可能不仅仅是处理体感反馈以监测敲击与节拍器(点击)之间的时间间隔,从而使受试者与外部事件保持同步。这个假设基于以下观察结果:(1)S1下似乎与敲击和点击的耦合程度相同;(2)这个源可能由最后一个事件(即敲击或点击)触发。在本研究中,我们使用122通道全头神经磁强计重新审视了这个假设。八名健康受试者将他们右手食指的敲击与以800毫秒恒定刺激间隔呈现的听觉节奏信号同步。为了测试最后一个事件触发S1下的假设,我们比较了敲击作为第一个和最后一个事件之后的神经磁活动。在听觉节奏手指敲击任务中,通常敲击领先于点击(负异步)。因此,敲击通常作为第一个事件发生。由于已经表明在敲击开始时提供额外的反馈会导致负异步减少,在第二次试验中,在敲击开始时呈现听觉反馈以增加正异步的数量(即敲击是最后一个事件)。由于未发现与正异步和负异步相关的S1下的潜伏期差异,本研究的结果不支持S1下由最后一个事件触发的假设。此外,与负异步相比,正异步后S1下的振幅显著降低。此外,当受试者产生正异步时,敲击持续时间(即敲击开始与敲击结束之间的时间)显著缩短。因此,S1下的振幅似乎受运动运动学的调节。这一观察结果与S1的激活仅与体感信息处理相关的观点非常一致。总之,我们的数据与位于初级体感皮层中的评估过程的假设相矛盾,并证实了S1下仅代表体感反馈信息处理的观点。

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