Hasegawa R, Sawaguchi T, Kubota K
Department of Behavioral and Brain Sciences, Primate Research Institute, Kyoto University, Kanrin, Inuyama, Aichi 484, Japan.
J Neurophysiol. 1998 Jan;79(1):322-33. doi: 10.1152/jn.1998.79.1.322.
To determine the role of the dorsolateral prefrontal cortex (PFC) in the selection of memory-guided saccadic eye movements, we recorded the activities of PFC neurons while macaque monkeys performed an oculomotor delayed matching-to-sample task. The task was designed to dissociate motor factors from visual factors in the selection and retention of the direction of the forthcoming saccade during delay periods after the visual cue but before the GO signal was presented. While the monkey fixated on a central fixation spot (FX period, 1 s), a sample cue (1 of 4 geometric figures) and a matching cue composed of two geometric figures were presented in succession (SC and MC periods, respectively, 0.5 s) with a brief delay (D1 period, 1 or 1.5 s). After another delay (D2 period, 1.5 s), the monkey made a saccade (GO period, <0.5 s) toward one of four locations (the goal) that had been indicated by the combination of the sample and matching cues in the MC period. We recorded the activities of 224 neurons in the periprincipal sulcal area of 3 hemispheres of 2 monkeys. Sixty-five neurons (29%) showed a significant increase in activity during the D2 period. Some of these also responded during other phases of the task (SC period, n = 32; D1, 22; MC, 53; GO, 47). Some of the activity during the D2(52/65, 80%) and GO (40/47, 85%) periods was associated with the direction of the forthcoming saccade ("direction selective"). Although most MC-period activities of D2 neurons were direction selective (38/53, 73%), a fraction of them (14/38) was also affected by both saccade direction and matching cue pattern. To compare quantitatively the contribution of motor (saccade direction) and visual (matching-cue pattern) factors to the activity of D2 neurons, we calculated directional and visual dependency indices (DDI and VDI) for each of the three periods (MC, D2, and GO). In both the D2 and GO periods, D2 neurons with high DDI values and low VDI values predominated. In the MC period, however, there was no significant difference between the distributions of DDI and VDI values. These findings suggest that PFC neurons store the direction of memory-guided saccades during a delay period before eye movement and that the same neurons may be involved in the decision-making process that underlies the selection of the saccade direction during the MC period.
为了确定背外侧前额叶皮层（PFC）在记忆引导的扫视眼动选择中的作用，我们在猕猴执行眼动延迟匹配样本任务时记录了PFC神经元的活动。该任务旨在在视觉提示后但在GO信号出现前的延迟期内，将即将进行的扫视方向的选择和保持过程中的运动因素与视觉因素区分开来。当猴子注视中央固定点时（注视期，1秒），依次呈现一个样本提示（4个几何图形中的1个）和一个由两个几何图形组成的匹配提示（分别为样本提示期和匹配提示期，各0.5秒），中间有短暂延迟（延迟1期，1或1.5秒）。在另一个延迟（延迟2期，1.5秒）后，猴子向四个位置之一（目标）进行扫视（GO期，<0.5秒），该位置在匹配提示期由样本和匹配提示的组合指示。我们记录了2只猴子3个半球主沟周围区域的224个神经元的活动。65个神经元（29%）在延迟2期活动显著增加。其中一些在任务的其他阶段也有反应（样本提示期，n = 32；延迟1期，22个；匹配提示期，53个；GO期，47个）。延迟2期（52/65，80%）和GO期（40/47，85%）的一些活动与即将进行的扫视方向相关（“方向选择性”）。尽管延迟2期神经元的大多数匹配提示期活动具有方向选择性（38/53，73%），但其中一部分（14/38）也受扫视方向和匹配提示模式的影响。为了定量比较运动（扫视方向）和视觉（匹配提示模式）因素对延迟2期神经元活动的贡献，我们计算了三个时期（匹配提示期、延迟2期和GO期）每个时期的方向依赖性指数（DDI）和视觉依赖性指数（VDI）。在延迟2期和GO期，具有高DDI值和低VDI值的延迟2期神经元占主导。然而，在匹配提示期，DDI和VDI值的分布没有显著差异。这些发现表明，PFC神经元在眼动前的延迟期存储记忆引导扫视的方向，并且相同的神经元可能参与了匹配提示期扫视方向选择背后的决策过程。
