Physiology of Active Vision Laboratory, Werner Reichardt Centre for Integrative Neuroscience, Tübingen University, Tübingen, Germany.
Hertie Institute for Clinical Brain Research, Tübingen University, Tübingen, Germany.
Front Neural Circuits. 2021 Mar 11;15:638429. doi: 10.3389/fncir.2021.638429. eCollection 2021.
Visual selection in primates is intricately linked to eye movements, which are generated by a network of cortical and subcortical neural circuits. When visual selection is performed covertly, without foveating eye movements toward the selected targets, a class of fixational eye movements, called microsaccades, is still involved. Microsaccades are small saccades that occur when maintaining precise gaze fixation on a stationary point, and they exhibit robust modulations in peripheral cueing paradigms used to investigate covert visual selection mechanisms. These modulations consist of changes in both microsaccade directions and frequencies after cue onsets. Over the past two decades, the properties and functional implications of these modulations have been heavily studied, revealing a potentially important role for microsaccades in mediating covert visual selection effects. However, the neural mechanisms underlying cueing effects on microsaccades are only beginning to be investigated. Here we review the available causal manipulation evidence for these effects' cortical and subcortical substrates. In the superior colliculus (SC), activity representing peripheral visual cues strongly influences microsaccade direction, but not frequency, modulations. In the cortical frontal eye fields (FEF), activity only compensates for early reflexive effects of cues on microsaccades. Using evidence from behavior, theoretical modeling, and preliminary lesion data from the primary visual cortex and microstimulation data from the lower brainstem, we argue that the early reflexive microsaccade effects arise subcortically, downstream of the SC. Overall, studying cueing effects on microsaccades in primates represents an important opportunity to link perception, cognition, and action through unaddressed cortical-subcortical neural interactions. These interactions are also likely relevant in other sensory and motor modalities during other active behaviors.
灵长类动物的视觉选择与眼球运动密切相关，而眼球运动是由皮质和皮质下神经网络产生的。当视觉选择是在不向所选目标进行注视眼动的情况下进行的，即隐蔽性视觉选择时，仍会涉及一类固定性眼球运动，称为微扫视。微扫视是在对静止点进行精确凝视固定时发生的小扫视，在用于研究隐蔽性视觉选择机制的外周提示范式中，微扫视表现出强烈的调制。这些调制包括提示后微扫视方向和频率的变化。在过去的二十年中，这些调制的特性和功能意义得到了广泛的研究，揭示了微扫视在介导隐蔽性视觉选择效应中的潜在重要作用。然而，提示对微扫视影响的神经机制才刚刚开始被研究。在这里，我们回顾了这些效应的皮质和皮质下基质的可用因果操纵证据。在上丘 (SC) 中，代表外周视觉提示的活动强烈影响微扫视的方向，但不影响频率调制。在皮质额眼区 (FEF) 中，活动仅补偿提示对微扫视的早期反射效应。我们利用来自行为、理论建模以及初级视觉皮层的初步损伤数据和来自下脑干的微刺激数据的证据，认为早期反射性微扫视效应起源于皮质下，位于 SC 下游。总的来说，在灵长类动物中研究提示对微扫视的影响代表了一个重要的机会，可以通过未解决的皮质-皮质下神经相互作用将感知、认知和行动联系起来。这些相互作用在其他主动行为中，在其他感觉和运动模态中也可能相关。
