VIBRATION-ENTRAINED AND PREMOVEMENT ACTIVITY IN MONKEY PRIMARY SOMATOSENSORY CORTEX
VIBRATION-ENTRAINED AND PREMOVEMENT ACTIVITY IN MONKEY PRIMARY SOMATOSENSORY CORTEX
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DOI：
10.1152/jn.1994.72.4.1654
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发表时间：
1994-10-01
影响因子：
2.5
通讯作者：
NELSON, RJ
中科院分区：
文献类型：
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作者：
LEBEDEV, MA;DENTON, JM;NELSON, RJ
1.初级躯体感觉皮层（SI）神经元在运动开始前表现出特征性活动。这种运动前活动（PMA）可能是由中央产生的，也可能是由外围输入产生的。我们检查了55个SI神经元（分别在区域3a、3b、1和2中有10、13、28和4个）的PMA，其活动被夹带到振动触觉刺激（即，与刺激时间相关）。我们试图确定振动夹带放电的时间特性是否会在整个反应时间段内发生变化，如果发生变化，这些变化是否可以由中央输入来解释。猴子的手腕弯曲和伸展，以响应其手掌的正弦振动（27，57或127 Hz）。持续振动，直到动物从初始保持位置移动至少5度。平均放电率（MFR），活动水平的测量，来自每个振动周期的尖峰的数量。振动和神经元放电之间的相关性被描述的平均相位（MP）的振动周期，尖峰发生。夹带的程度被量化为同步性（Synch），这是一个统计参数，可以从0（无夹带）变化到1（恒定相位下的响应）。观察到运动前MFR增加（激活）和减少（抑制）。此外，在同一神经元（2事件PMA）中经常观察到两种MFR变化。许多MFR的变化，特别是第一次在两个事件的PMA，之前肌电图（EMG）的发病。前EMG MFR的变化更经常有相同的迹象，无论是屈曲和伸展运动，而不是有相反的迹象。然而，在相同的频率下，对于不同的运动方向，EMG后PMA事件具有相同或相反的符号。我们认为，前肌电PMA的起源不同于运动相关的外周反应.运动前激活伴随着MP的变化，对应于对正在进行的振动刺激的早期反应和同步反应的减少。运动前抑制与MP和Synch的一致变化无关。我们认为，在运动前激活，异步（不相关的振动）信号集成与振动输入。这些异步信号可能使神经元更有可能放电，并且相对于振动刺激更早地放电。异步组件也可能会破坏振动夹带的活动模式。从这些数据中，我们得出结论，最忠实地代表感觉周边的SI神经元的活动调制自愿运动之前。我们认为，中央起源的输入可能有助于这种运动前调制。据推测，中枢输入的作用可能是准备SI的感觉活动的变化，导致自愿运动。运动前的异步信号，无论是中央和周边的起源，破坏的振动刺激的SI神经元编码的保真度。这种SI神经元对感觉输入的表征质量的恶化可能与运动前感知的触觉阈值升高和运动前体感诱发电位降低的现象有关。
1. Primary somatosensory cortical(SI) neurons exhibit characteristic activity before the initiation of movements. This premovement activity (PMA) may result from centrally generated as well as from peripheral inputs. We examined PMA for 55 SI neurons (10, 13, 28, and 4 in areas 3a, 3b, 1, and 2, respectively) with activity that was entrained to vibrotactile stimulation (i.e., was temporally correlated with the stimulus). We sought to determine whether the temporal characteristics of vibration-entrained discharges would change throughout the reaction time period, and, if they did, whether these changes might be accounted for by central inputs.2. Monkeys made wrist flexions and extensions in response to sinusoidal vibration (27, 57, or 127 Hz) of their palms. Vibration remained on until the animal moved at least 5 degrees from the initial hold position. Mean firing rate (MFR), a measure of the level of activity, was derived from the number of spikes per vibratory cycle. The correlation between the vibration and the neuronal firing was described by the mean phase (MP) of the vibratory cycle at which spikes occurred. The degree of entrainment was quantified as synchronicity (Synch), a statistical parameter that could change from 0 for no entrainment to 1 for responses at a constant phase.3. Premovement MFR increases (activation) and decreases (suppression) were observed. Moreover, two changes in MFR often were observed for the same neuron (2-event PMA). Many MFR shifts, especially the first in the two-event PMA, preceded electromyographic (EMG) onset. The pre-EMG MFR shifts more often had the same sign both for flexion and extension movements rather than having opposite signs. However, with equal frequency, post-EMG PMA events had the same or opposite sign for different movement directions. We suggest that the pre-EMG PMA has an origin different from movement-related peripheral reafference.4. Premovement activation was accompanied by shifts of MP corresponding to earlier responses to the ongoing vibratory stimulus and by decreases of response Synch. Premovement suppression was not associated with consistent shifts of MP and Synch. We suggest that during premovement activation, asynchronous (uncorrelated with vibration) signals are integrated with the vibratory input. These asynchronous signals may make neurons more likely to discharge and to do so earlier with respect to the vibratory stimulus. The asynchronous component may also disrupt the vibration-entrained activity pattern.5. From these data we conclude that the activity of SI neurons that most faithfully represent the sensory periphery is modulated before voluntary movements. We suggest that inputs of central origin may contribute to this premovement modulation. Presumably, the role of the central inputs may be to prepare SI for changes in sensory activity that result from voluntary movement. Premovement asynchronous signals, both of central and peripheral origin, disrupt the fidelity of coding of the vibratory stimulus by SI neurons. This deterioration of the quality of representation of sensory inputs by SI neurons may be related to the phenomena of premovement elevation of the tactile threshold of perception and of premovement decrease of somatosensory-evoked potentials.