Fee M S, Mitra P P, Kleinfeld D
Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974, USA.
J Neurophysiol. 1997 Aug;78(2):1144-9. doi: 10.1152/jn.1997.78.2.1144.
We report on the relationship between single-unit activity in primary somatosensory vibrissa cortex of rat and the rhythmic movement of vibrissae. Animals were trained to whisk freely in air in search of food. Electromyographic (EMG) recordings from the mystatial pads served as a reference for the position of the vibrissae. A fast, oscillatory component in single-unit spike trains is correlated with vibrissa position within the whisk cycle. The phase of the correlation for different units is broadly distributed. A second, slowly varying component of spike activity correlates with the amplitude of the whisk cycle. For some units, the phase and amplitude correlations were of sufficient strength to allow the position of the whiskers to be accurately predicted from a single spike train. To determine whether the observed patterned spike activity was driven by motion of the vibrissae, as opposed to central pathways, we reversibly blocked the contralateral facial motor nerve during the behavioral task so that the rat whisked only on the ipsilateral side. The ipsilateral EMG served as a reliable reference signal. The fast, oscillatory component of the spike-EMG correlation disappears when the facial motor nerve is blocked. This implies that the position of vibrissae within a cycle is encoded through direct sensory activation. The slowly varying component of the spike-EMG correlation is unaffected by the block. This implies that the amplitude of whisking is likely to be mediated by corollary discharge. Our results suggest that motor cortex does not relay a reference signal to sensory cortex for positional information of the vibrissae during whisking.
我们报告了大鼠初级体感触须皮层中的单神经元活动与触须节律性运动之间的关系。动物经过训练后可在空中自由摆动触须以寻找食物。从颏肌垫记录的肌电图（EMG）作为触须位置的参考。单神经元放电序列中的快速振荡成分与触须周期内的触须位置相关。不同神经元的相关相位分布广泛。放电活动的第二个缓慢变化成分与触须周期的幅度相关。对于一些神经元，相位和幅度相关性足够强，以至于可以从单个放电序列中准确预测触须的位置。为了确定观察到的有模式的放电活动是由触须运动驱动的，而不是由中枢通路驱动的，我们在行为任务期间可逆地阻断对侧面神经，以使大鼠仅在同侧摆动触须。同侧EMG作为可靠的参考信号。当面神经被阻断时，放电 - EMG相关性的快速振荡成分消失。这意味着触须在一个周期内的位置是通过直接的感觉激活来编码的。放电 - EMG相关性的缓慢变化成分不受阻断的影响。这意味着摆动幅度可能是由伴随放电介导的。我们的结果表明，在摆动过程中，运动皮层不会将触须位置信息的参考信号传递给感觉皮层。
