New Zealand Brain Research Institute, Christchurch, New Zealand.
Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan.
Eur J Neurosci. 2019 Jul;50(2):1892-1910. doi: 10.1111/ejn.14365. Epub 2019 Feb 25.
Human cognitive behavior is predictive rather than reflexive because of volitional action preparation. Recent studies have shown that the covert process of volitional action preparation can be decoded from overt fixational eye movements of fixational/microsaccades and pupil dilation. Ocular drift, the slowest fixational eye movements, is also under the active neural control, but its relationship with cognitive behavior is unknown. Here, we examined whether ocular drift also reflects volitional action preparation. We analyzed ocular drift while adult humans maintained fixation on a central visual stimulus as they prepared to generate a volitional saccade. We adopted the antisaccade paradigm in which subjects generate a targeting saccade toward the opposite direction of a peripheral visual stimulus. Our findings are the following five points. First, ocular drift was slower when subjects prepared for targeting saccade initiation than when such preparation was unnecessary. Second, ocular drift was slowed down with elapsed time from fixation initiation, which was associated with the facilitation of targeting saccade initiation. Third, ocular drift was further slowed on correct antisaccade trials than when subjects failed to suppress targeting saccades toward peripheral stimuli. Fourth, such correlation with antisaccade performance was observed immediately after fixation initiation in ocular drift, but it emerged more slowly in the other fixational eye movements. Fifth, subjects with unstable fixation because of faster ocular drift had poorer antisaccade performance. We suggest that fixation stability measured by ocular drift can be used to decode the covert process of volitional action preparation along with the other fixational eye movements.
人类的认知行为是预测性的，而不是反射性的，因为它是意志行动的准备。最近的研究表明，意志行动准备的隐蔽过程可以从注视/微扫视和瞳孔扩张的外显注视固定眼动中解码出来。眼漂移是最慢的注视性眼球运动，也受到主动神经控制，但它与认知行为的关系尚不清楚。在这里，我们研究了眼漂移是否也反映了意志行动的准备。当成年人为了进行意志性扫视而准备注视中央视觉刺激时，我们分析了眼漂移。我们采用了反扫视范式，在这种范式中，被试者会对周边视觉刺激的相反方向生成一个目标性扫视。我们的发现有以下五点。首先，当被试者准备进行目标性扫视启动时，眼漂移比不需要这种准备时更慢。其次，眼漂移随着从注视开始的时间流逝而减慢，这与目标性扫视启动的促进有关。第三，在正确的反扫视试验中，眼漂移进一步减慢，而当被试者未能抑制对周边刺激的目标性扫视时，眼漂移没有减慢。第四，这种与反扫视表现的相关性在眼漂移中立即在注视开始后观察到，但在其他注视性眼球运动中出现得更慢。第五，由于眼漂移较快而导致注视不稳定的被试者，其反扫视表现较差。我们认为，眼漂移测量的注视稳定性可以与其他注视性眼球运动一起，用来解码意志性行动准备的隐蔽过程。
