Fixation and saccade generation by the frontal eye field

众所周知，前额眼野（FEF）负责眼跳跃性运动的产生。最近，研究发现FEF也参与了平滑追逐眼动和收敛眼动的产生。相比之下，本研究的目的是在FEF中确定电刺激抑制猴子跳眼运动的区域。此外，通过改变不同的电刺激参数，研究了电刺激对扫视的抑制作用。为了达到这个目的，猴子们用传统的方式进行训练，让它们在视觉引导下扫视面前屏幕上的目标。然后，系统地调查FEF，以找到刺激抑制视觉引导的扫视的区域。皮层内微刺激的刺激强度限制在50 μA以下。在刺激产生扫视的经典FEF的相当大的区域内，有强度的刺激产生的扫视可以抑制刺激侧同侧的扫视，但不能抑制对侧的扫视。相比之下，在100 μA下刺激经典FEF附近无眼跳的区域，在小于50 μA的刺激下，在单侧和对侧均容易抑制眼跳。刺激该位点可抑制8个方向的扫视，且不同方向对扫视的抑制强度基本相等。这种抑制随着刺激时间的延长而持续。单侧和对侧对眼动的抑制阈值低至10 μA，且几乎相等。为了检查FEF中这个抑制区域的神经元的特性，在固定任务期间记录了峰值。即使没有固定目标，该区域的神经元在固定期间也表现出活动增加。这些神经元在任何方向的扫视开始时停止放电。这些神经元对固定任务的反应的进一步特性现在正在研究中。少

It has been well known that the frontal eye field (FEF) is responsible for generation of saccadic eye movements. Recently, it turns out that the FEF is also involved in generating smooth pursuit eye movement and convergence eye movement.In contrast, the present study was aimed at identifying the area in the FEF where electrical stimulation produced suppression of saccadic eye movements in the monkey. In addition, the properties of the suppression on saccades were investigated by changing various parameters for the electrical stimulation. For this purpose, the monkeys were trained in a conventional way to make visually-guided saccades to a visual target on the screen in front of them. Then, the FEF was systematically surveyed to find an area whose stimulation suppresses visually-guided saccades. Stimulus intensity for intracortical microstimulation was limited to less than 50 μA. In a fairly wide area of the classical FEF where stimulation produced saccades, stimulation with intensities … More sub threshold for saccade generation could suppress the saccades ipsilateral to the stimulation side, but not the saccades contralateral to it. In contrast, stimulation of the area adjacent to the classical FEF where no saccades were evoked at 100 μA, stimulation at less than 50 μA could easily suppress saccades in both ipsi- and contralateral directions. Stimulation of this site suppressed saccades in 8 directions covering all directions, and strengths of the suppression on the saccades in these different directions were almost equal. This suppression continued as the stimulus duration was increased. Thresholds for the suppression on saccades in ipsi- and contralateral directions were as low as 10 μA and almost equal. To examine the properties of neurons in this suppression area of the FEF, spikes were recorded during the fixation task. Neurons in this area showed increase of activities during the fixation even without a fixation target. These neurons stopped firing at the onset of saccades in any directions. Further properties of these neurons in response to the fixation task are now being investigated. Less