Hanes D P, Patterson W F, Schall J D
Vanderbilt Vision Research Center, Department of Psychology, Vanderbilt University, Nashville, Tennessee 37240, USA.
J Neurophysiol. 1998 Feb;79(2):817-34. doi: 10.1152/jn.1998.79.2.817.
A new approach was developed to investigate the role of visual-, movement-, and fixation-related neural activity in gaze control. We recorded unit activity in the frontal eye fields (FEF), an area in frontal cortex that plays a central role in the production of purposeful eye movements, of monkeys (Macaca mulatta) performing visually and memory-guided saccades. The countermanding paradigm was employed to assess whether single cells generate signals sufficient to control movement production. The countermanding paradigm consists of a task that manipulates the monkeys' ability to withhold planned saccades combined with an analysis based on a race model that provides an estimate of the time needed to cancel the movement that is being prepared. We obtained clear evidence that FEF neurons with eye movement-related activity generate signals sufficient to control the production of gaze shifts. Movement-related activity, which was growing toward a trigger threshold as the saccades were prepared, decayed in response to the stop signal within the time required to cancel the saccade. Neurons with fixation-related activity were less common, but during the countermanding paradigm, these neurons exhibited an equally clear gaze-control signal. Fixation cells that had a pause in firing before a saccade exhibited elevated activity in response to the stop signal within the time that the saccade was cancelled. In contrast to cells with movement or fixation activity, neurons with only visually evoked activity exhibited no evidence of signals sufficient to control the production of gaze shifts. However, a fraction of tonic visual cells exhibited a reduction of activity once a saccade command had been cancelled even though the visual target was still present in the receptive field. These findings demonstrate the use of the countermanding paradigm in identifying neural signatures of motor control and provide new information about the fine balance between gaze shifting and gaze holding mechanisms.
一种新的方法被开发出来，用于研究视觉、运动和注视相关神经活动在注视控制中的作用。我们记录了恒河猴（猕猴）在进行视觉和记忆引导扫视时，额叶眼区（FEF）的单位活动。额叶眼区是额叶皮层中的一个区域，在有目的的眼球运动产生中起核心作用。采用反指令范式来评估单个细胞是否产生足以控制运动产生的信号。反指令范式包括一项操纵猴子抑制计划扫视能力的任务，并结合基于竞争模型的分析，该模型可估计取消正在准备的运动所需的时间。我们获得了明确的证据，表明具有眼动相关活动的FEF神经元产生的信号足以控制注视转移的产生。在准备扫视时，向触发阈值增长的运动相关活动，在取消扫视所需的时间内，响应停止信号而衰减。具有注视相关活动的神经元较少见，但在反指令范式期间，这些神经元表现出同样清晰的注视控制信号。在扫视前放电暂停的注视细胞，在扫视被取消的时间内，响应停止信号而活动增强。与具有运动或注视活动的细胞不同，仅具有视觉诱发活动的神经元没有显示出足以控制注视转移产生的信号的证据。然而，一部分持续性视觉细胞，即使视觉目标仍在感受野中，一旦扫视指令被取消，其活动就会减少。这些发现证明了反指令范式在识别运动控制神经特征方面的应用，并提供了关于注视转移和注视保持机制之间精细平衡的新信息。
