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美国卫生研究院文献>The Journal of Neuroscience
>Spatial–Temporal Distribution of Whisker-Evoked Activity in Rat Somatosensory Cortex and the Coding of Stimulus Location
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Spatial–Temporal Distribution of Whisker-Evoked Activity in Rat Somatosensory Cortex and the Coding of Stimulus Location
Rats use their facial vibrissae (“whiskers”) to locate and identify objects. To learn about the neural coding of contact between whiskers and objects, we investigated the representation of single-vibrissa deflection by populations of cortical neurons. Microelectrode arrays, arranged in a geometric 10 × 10 grid, were inserted into the thalamo-recipient layers of “barrel cortex” (the vibrissal region of somatosensory cortex) in urethane-anesthetized rats, and neuronal activity across large sets of barrel-columns was measured. Typically, 5 msec after deflection of a whisker a 0.2 mm2 focus of activity emerged. It rapidly expanded, doubling in size by 7 msec, before retracting and disappearing 28–59 msec after stimulus onset. The total territory engaged by the stimulus ranged from 0.5 to 2.9 mm2 (2–11 barrels). Stimulus site dictated the domain of activity. To quantify the coding of whisker location, we applied the population d′ measure of discriminability. Activity patterns elicited by two whiskers were highly discriminable at the initial cortical response; peak discriminability typically occurred within 16 msec of stimulus onset. To determine how widely information about stimulus location was distributed, we measured population d′ while excluding response data from the on-center electrodes of the two tested whiskers. Response patterns remained discriminable, indicating that information about stimulus location was distributed across barrel cortex. Taken together, these results show that single-whisker deflections are represented in a multicolumn region constrained by barrel cortex map topography. The nature of this coding allows information about stimulus location to be coded extremely rapidly and unambiguously by one to two spikes per neuron.
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机译:老鼠使用其面部触须(“胡须”)来定位和识别物体。要了解晶须与物体之间接触的神经编码,我们研究了皮层神经元群体对单须挠度的表示。将微电极阵列以10×10的几何形状排列,插入到氨基甲酸乙酯麻醉大鼠的“桶状皮质”(体感皮层的振动区域)的丘脑受体层中,整个大桶状柱的神经元活动为测量。通常,晶须偏转5毫秒后,会出现0.2 mm 2 sup>的活动焦点。它迅速扩展,大小增加了7毫秒,然后在刺激开始后缩回并消失28-59毫秒。刺激参与的总领土范围为0.5至2.9 mm 2 sup>(2-11桶)。刺激部位决定了活动范围。为了量化晶须位置的编码,我们应用了区分度的总体d'度量。在最初的皮层反应中,由两个晶须引起的活动模式可被高度区分。峰值可分辨性通常发生在刺激发作的16毫秒内。为了确定有关刺激位置的信息分布的广泛程度,我们测量了人口d',同时从两个测试的晶须的中心电极上排除了响应数据。响应模式仍然是可分辨的,表明有关刺激位置的信息分布在整个桶状皮质。综上所述,这些结果表明,单须偏转在受圆柱皮质图形图约束的多列区域中表示。这种编码的性质允许对刺激位置的信息进行极快速且明确的编码,每个神经元编码一到两个尖峰。
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