Centre of Behavioural and Cognitive Sciences, University of Allahabad, Allahabad, India.
Eur J Neurosci. 2019 Jan;49(2):232-249. doi: 10.1111/ejn.14220. Epub 2018 Nov 15.
An inhibitory control is exerted when the context in which a movement has been planned changes abruptly making the impending movement inappropriate. Neurons in the frontal eye field and superior colliculus steadily increase activity before a saccadic eye movement, but cease the rise below a threshold when an impending saccade is withheld in response to an unexpected stop-signal. This type of neural modulation has been majorly considered as an outcome of a race between preparatory and inhibitory processes ramping up to reach a decision criterion. An alternative model claims that the rate of saccade planning is diminished exclusively when the stop-signal is detected within a stipulated period. However, due to a dearth of empirical evidence in support of the latter model, it remains unclear how the detectability of the stop-signal influences saccade inhibition. In our study, human participants selected a visual target to look at by discriminating a go-cue. Infrequently they cancelled saccade and reported whether they saw the stop-signal. The go-cue and stop-signal both were embedded in a stream of irrelevant stimuli presented in rapid succession. Participants exhibited difficulty in detection of the stop-signal when presented almost immediately after the go-cue. We found a robust relationship between the detectability of the stop-signal and the odds of saccade inhibition. Saccade latency increased exponentially with the maximum time available for processing the stop-signal before gaze shifted. A model in which the stop-signal onset spontaneously decelerated progressive saccade planning with the magnitude proportional to its detectability accounted for the data.
当计划中的运动的上下文突然发生变化，使得即将进行的运动变得不合适时，就会产生抑制控制。在进行扫视眼动之前，额眼区和上丘中的神经元会稳定地增加活动，但当即将进行的扫视眼动因对意外的停止信号做出反应而被抑制时，它们会在低于阈值的水平停止上升。这种类型的神经调节主要被认为是预备和抑制过程之间的竞争结果，这两个过程都在不断增强，以达到决策标准。另一种模型声称，只有在规定的时间内检测到停止信号时，扫视计划的速度才会降低。然而，由于缺乏支持后一种模型的经验证据，停止信号的可检测性如何影响扫视抑制仍然不清楚。在我们的研究中，人类参与者通过辨别 Go 线索来选择要观看的视觉目标。很少情况下，他们会取消扫视并报告是否看到了停止信号。Go 线索和停止信号都嵌入在快速连续呈现的无关刺激流中。当停止信号几乎在 Go 线索之后立即呈现时，参与者很难检测到停止信号。我们发现停止信号的可检测性与扫视抑制的可能性之间存在很强的关系。扫视潜伏期随着在注视转移之前处理停止信号的最长可用时间呈指数级增加。一个模型表明，停止信号的起始会自发地减缓渐进性扫视计划，其幅度与可检测性成正比，该模型可以解释数据。
