Peripheral-to-foveal cortico-collicular processing of visual information across eye movements

眼跳运动会导致视觉上的不确定性，这是因为它们在整个视网膜上快速地翻译环境的图像。此外，由于视觉系统的很大一部分是以视网膜为基础组织的，因此每次发生眼跳时，代表多个脑区中心凹视网膜成像区的神经元经历的扫视后场景部分与眼动开始之前的场景部分不同。这一点，再加上眼球运动开始后的感觉输入(由于长时间的传入延迟和由眼跳引起的强烈运动模糊)，表明需要一种机制来桥接跨眼跳视觉处理。这种桥接既需要在时间上发生(跨越眼跳持续时间)，也需要在空间上发生(将眼球运动目标的视网膜周边前眼跳图像与中心凹后眼跳版本联系起来)。在不同的视网膜组织的神经元群体之间，视觉信息的跨跳外周到中心凹转移可能是实现这种桥梁的一种手段，这种转移的感知证据是存在的。在这个项目中，我们将揭开与视觉信息跨眼跳外周到中心凹转移相关的皮质和皮质下机制。我们将证明，在上丘(SC)和初级视觉皮质(V1)中，存在稳定的眼跳目标的外围视觉特征信息到中心凹视觉表征的预测性重新映射。我们还将因果地证明，这种重新映射可以在SC运动脉冲本身启动(众所周知，SC运动脉冲通过向脑干和小脑运动控制核团的下游投射来驱动眼球运动)。这种跳跃是通过在SC运动脉冲中嵌入感官调节信号来实现的，这意味着SC中的扫视命令同时也代表了外围眼跳目标的视觉外观。我们认为，赋予SC运动脉冲这样的感觉调节信号允许SC为视觉区域提供桥接感知的外围场景预览；也就是说，由于SC运动脉冲与眼跳在时间上重合，嵌入其中的场景预览恰好在视觉(通过感觉传入)最不确定时可用(在眼球内)。最后，由于SC有向上的反馈投射到大脑皮层，我们将调查SC的感觉调节运动爆发活动是否对视觉特征在大脑皮层水平上跨扫视重新映射到中心凹至关重要，或者大脑皮层-大脑皮层的相互作用(可能通过V4区)是否足够。我们的实验将揭示高度新颖的机械洞察力，即通过眼球运动对视觉信息进行外周到中心凹皮质-大脑皮质的处理。

Saccadic eye movements cause substantial visual uncertainty due to the rapidity with which they translate images of the environment across the retina. Moreover, because a large portion of the visual system is organized retinotopically, every time a saccade occurs, neurons representing the foveal retinal image region in multiple brain areas experience a different post-saccadic scene portion than the scene portion that they experience before eye movement onset. This, coupled with the fact that post-saccadic sensory input arrives well after eye movement onset (due to long afferent processing delays and strong motion blur caused by saccades), suggests a need for a mechanism to bridge trans-saccadic visual processing. Such bridging needs to happen both in time (across saccade duration) as well as in space (linking a retinotopically peripheral pre-saccadic image of the eye movement target to a foveal post-saccadic version of it). Trans-saccadic peripheral-to-foveal transfer of visual information between different retinotopically organized populations of neurons could be a means to realize exactly such a bridge, and perceptual evidence for this transfer exists. In this project, we will unravel the cortical and subcortical mechanisms associated with trans-saccadic peripheral-to-foveal transfer of visual information. We will demonstrate that there is a predictive remapping of peripheral visual feature information of a stable saccade target to foveal visual representations in both the superior colliculus (SC) and primary visual cortex (V1). We will also causally demonstrate that such remapping can be jumpstarted in the SC motor bursts themselves (which are known to drive eye movements via downstream projections to brainstem and cerebellar motor control nuclei). This jumpstarting happens via embedding a sensory-tuned signal in the SC motor bursts, meaning that saccade commands in the SC simultaneously also represent the visual appearance of peripheral saccade targets. We argue that endowing SC motor bursts with such a sensory tuning signal allows the SC to provide visual areas with a peripheral scene preview for bridging perception; that is, because SC motor bursts are temporally coincident with saccades, the scene preview embedded in them is available exactly when vision (via sensory afference) is most uncertain (intra-saccadically). Finally, because the SC has ascending feedback projections to the cortex, we will investigate whether the SC’s sensory-tuned motor burst activity is critical for trans-saccadic remapping of visual features to the fovea at the cortical level, or whether cortico-cortical interactions (perhaps via area V4) are sufficient. Our experiments will reveal highly novel mechanistic insights on peripheral-to-foveal cortico-collicular processing of visual information across eye movements.