Rajan R, Browning Andrew S, Bourke Justin L
Department of Physiology, Monash University, Clayton, Victoria 3800, Australia.
Eur J Neurosci. 2007 Apr;25(8):2383-403. doi: 10.1111/j.1460-9568.2007.05481.x.
Rats whisk to explore their environment and obtain information on object features, and the responses of somatosensory cortical neurones must precisely encode aspects of whisker movements. Using trapezoidal stimuli to deflect whiskers, with a wide range of velocities and amplitudes of whisker protraction, we recorded responses from a relatively homogeneous population of isolated cells and neuronal multiunits within the postero-medial barrel sub-field of somatosensory cortex, and analysed responses in an early post-stimulus-onset window. For 92% of neurones the function relating response strength to velocity was a saturating sigmoid but there were differences between neurones in the slopes and ranges over which responses changed. Responses of other neurones were non-monotonic, with response strength decaying at very high whisker deflection velocities. Generally, barrel cortex neurones were responsive to a much wider range of whisker protraction velocities than hitherto reported, especially to much slower velocities than generally assumed to be the main range of sensitivity. This carries implications for coding of whisker deflection velocity, a parameter that appears to be a significant information-bearing element of natural whisking. The effect of amplitude of deflection upon neural responses was evident in only approximately 24% of units and only when the dominant velocity effect had saturated.
大鼠通过摆动触须来探索环境并获取物体特征信息，体感皮层神经元的反应必须精确编码触须运动的各个方面。我们使用梯形刺激使触须偏转，触须前伸的速度和幅度范围很广，记录了体感皮层后内侧桶状亚区内相对同质的分离细胞和神经元多单元群体的反应，并在刺激开始后的早期窗口分析反应。对于92%的神经元，反应强度与速度的关系函数是一个饱和的S形曲线，但不同神经元在反应变化的斜率和范围上存在差异。其他神经元的反应是非单调的，在触须偏转速度非常高时反应强度会衰减。一般来说，桶状皮层神经元对触须前伸速度的响应范围比迄今报道的要宽得多，特别是对比通常认为的主要敏感范围慢得多的速度。这对触须偏转速度的编码有影响，触须偏转速度这个参数似乎是自然触须摆动中一个重要的信息承载元素。只有约24%的单元中，偏转幅度对神经反应的影响才明显，且只有在主要的速度效应饱和时才会出现。
