Massachusetts Institute of Technology.
J Cogn Neurosci. 1989 Fall;1(4):317-26. doi: 10.1162/jocn.1989.1.4.317.
Microstimulation of many saccadic centers in the brain produces eye movements that are not consistent with either a strictly retinal or strictly head-centered coordinate coding of eye movements. Rather, stimulation produces some features of both types of coordinate coding. Recently we demonstrated a neural network model that was trained to localize the position of visual stimuli in head-centered coordinates at the output using inputs of eye and retinal position similar to those converging on area 7a of the posterior parietal cortex of monkeys (Zipser & Andersen 1988; Andersen & Zipser 1988). Here we show that microstimulation of this trained network, achieved by fully activating single units in the middle layer, produces "saccades" that are very much like the saccades produced by stimulating the brain. The activity of the middle-layer units can be considered to code the desired location of the eyes in head-centered coordinates; however, stimulation of these units does not produce the saccades predicted by a classical head-centered coordinate coding because the location in space appears to be coded in a distributed fashion among a population of units rather than explicitly at the level of single cells.
大脑中许多扫视中心的微刺激会产生与视网膜或头部中心坐标编码都不一致的眼球运动。相反，刺激会产生这两种坐标编码的一些特征。最近，我们展示了一个神经网络模型，该模型经过训练，使用类似于会聚到猴子后顶叶皮层 7a 区的眼和视网膜位置的输入，在头部中心坐标中定位视觉刺激的位置（Zipser 和 Andersen 1988；Andersen 和 Zipser 1988）。在这里，我们表明，通过完全激活中间层的单个单元来实现对这个经过训练的网络的微刺激，会产生非常类似于刺激大脑产生的“扫视”。中间层单元的活动可以被认为是在头部中心坐标中对眼睛的期望位置进行编码；然而，这些单元的刺激并不会产生经典头部中心坐标编码所预测的扫视，因为空间中的位置似乎是在单元群体中以分布式的方式编码的，而不是在单个细胞的水平上明确编码的。
