Boussaoud D, Barth T M, Wise S P
Laboratory of Neurophysiology, National Institute of Mental Health, Poolesville, MD 20837.
Exp Brain Res. 1993;93(3):423-34. doi: 10.1007/BF00229358.
Previous reports have argued that single neurons in the ventral premotor cortex of rhesus monkeys (PMv, the ventrolateral part of Brodmann's area 6) typically show spatial response fields that are independent of gaze angle. We reinvestigated this issue for PMv and also explored the adjacent prearcuate cortex (PAv, areas 12 and 45). Two rhesus monkeys were operantly conditioned to press a switch and maintain fixation on a small visual stimulus (0.2 degree x 0.2 degree) while a second visual stimulus (1 degree x 1 degree or 2 degrees x 2 degrees) appeared at one of several possible locations on a video screen. When the second stimulus dimmed, after an unpredictable period of 0.4-1.2 s, the monkey had to quickly release the switch to receive liquid reinforcement. By presenting stimuli at fixed screen locations and varying the location of the fixation point, we could determine whether single neurons encode stimulus location in "absolute space" or any other coordinate system independent of gaze. For the vast majority of neurons in both PMv (90%) and PAv (94%), the apparent response to a stimulus at a given screen location varied significantly and dramatically with gaze angle. Thus, we found little evidence for gaze-independent activity in either PMv or PAv neurons. The present result in frontal cortex resembles that in posterior parietal cortex, where both retinal image location and eye position affect responsiveness to visual stimuli.
先前的报告认为，恒河猴腹侧运动前皮质（PMv，布罗德曼6区的腹外侧部分）中的单个神经元通常表现出与注视角度无关的空间反应域。我们重新研究了PMv的这个问题，并探索了相邻的弓状前皮质（PAv，12区和45区）。对两只恒河猴进行操作性条件训练，使其按压开关并在一个小视觉刺激（0.2度×0.2度）上保持注视，同时第二个视觉刺激（1度×1度或2度×2度）出现在视频屏幕上几个可能位置中的一个。当第二个刺激变暗时，在0.4 - 1.2秒的不可预测时间段后，猴子必须迅速松开开关以获得液体奖励。通过在固定的屏幕位置呈现刺激并改变注视点的位置，我们可以确定单个神经元是在“绝对空间”还是在与注视无关的任何其他坐标系中编码刺激位置。对于PMv（90%）和PAv（94%）中的绝大多数神经元，在给定屏幕位置对刺激的明显反应随注视角度而显著且剧烈地变化。因此，我们在PMv或PAv神经元中几乎没有发现与注视无关的活动证据。额叶皮质的当前结果类似于后顶叶皮质的结果，在那里视网膜图像位置和眼睛位置都会影响对视觉刺激的反应性。
