Knutsen Per Magne, Ahissar Ehud
Department of Neurobiology, Weizmann Institute for Science, Rehovot 76100, Israel.
Trends Neurosci. 2009 Feb;32(2):101-9. doi: 10.1016/j.tins.2008.10.002. Epub 2008 Dec 13.
It has been argued whether internal representations are encoded using a universal ('the neural code') or multiple codes. Here, we review a series of experiments that demonstrate that tactile encoding of object location via whisking employs an orthogonal, triple-code scheme. Rats, and other rodents, actively move the whiskers back and forth to localize and identify objects. Neural recordings from primary sensory afferents, along with behavioral observations, demonstrate that vertical coordinates of contacted objects are encoded by the identity of activated afferents, horizontal coordinates by the timing of activation and radial coordinates by the intensity of activation. Because these codes are mutually independent, the three-dimensional location of an object could, in principle, be encoded by individual afferents during single whisker-object contacts. One advantage of such a same-neuron-different-codes scheme over the traditionally assumed same-code-different-neurons scheme is a reduction of code ambiguity that, in turn, simplifies decoding circuits.
关于内部表征是使用通用编码（“神经编码”）还是多种编码进行编码一直存在争议。在此，我们回顾一系列实验，这些实验表明通过胡须运动对物体位置进行触觉编码采用了一种正交的三编码方案。大鼠和其他啮齿动物会主动来回移动胡须以定位和识别物体。来自初级感觉传入神经的神经记录以及行为观察表明，被接触物体的垂直坐标由被激活传入神经的身份编码，水平坐标由激活时间编码，径向坐标由激活强度编码。由于这些编码相互独立，原则上，在单个胡须与物体接触期间，物体的三维位置可以由单个传入神经进行编码。与传统假设的同编码不同神经元方案相比，这种同一神经元不同编码方案的一个优点是减少了编码的模糊性，进而简化了解码电路。
