Petersen R S, Diamond M E
Cognitive Neuroscience Sector, International School for Advanced Studies, 34014 Trieste, Italy.
J Neurosci. 2000 Aug 15;20(16):6135-43. doi: 10.1523/JNEUROSCI.20-16-06135.2000.
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 x 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 mm(2) 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 mm(2) (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.
大鼠利用其面部触须（“胡须”）来定位和识别物体。为了了解触须与物体接触的神经编码，我们研究了皮层神经元群体对单个触须偏转的表征。将以几何10×10网格排列的微电极阵列插入经乌拉坦麻醉的大鼠的“桶状皮层”（体感皮层的触须区域）的丘脑接受层，并测量大量桶状柱上的神经元活动。通常，触须偏转5毫秒后，会出现一个0.2平方毫米的活动焦点。它迅速扩展，在7毫秒时大小翻倍，然后在刺激开始后28 - 59毫秒缩回并消失。刺激所涉及的总面积在0.5至2.9平方毫米之间（2 - 11个桶状区）。刺激部位决定了活动区域。为了量化触须位置的编码，我们应用了可辨别性的群体d'测量方法。在最初的皮层反应中，由两根触须引发的活动模式具有高度可辨别性；峰值可辨别性通常在刺激开始后16毫秒内出现。为了确定关于刺激位置的信息分布有多广泛，我们在排除两个测试触须的中心电极的反应数据的同时测量群体d'。反应模式仍然可辨别，这表明关于刺激位置的信息分布在桶状皮层上。综上所述，这些结果表明单个触须的偏转在由桶状皮层图谱地形所限制的多柱区域中得到表征。这种编码的性质使得关于刺激位置的信息能够由每个神经元一到两个尖峰极其快速且明确地编码。
