Nativ Yarden, Bouhnik Tomer, Slovin Hamutal
The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat Gan 5290002, Israel.
The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat Gan 5290002, Israel
J Neurosci. 2025 Apr 2;45(14):e1547242025. doi: 10.1523/JNEUROSCI.1547-24.2025.
Our eyes are never still. Even when we attempt to fixate, the visual gaze is never motionless, as we continuously perform miniature oculomotor movements termed as fixational eye movements. The fastest eye movements during the fixation epochs are termed microsaccades (MSs) that are leading to continual motion of the visual input, affecting mainly neurons in the fovea. Yet our vision appears to be stable. To explain this gap, previous studies suggested the existence of an extraretinal input (ERI) into the visual cortex that can account for the motion and produce visual stability. Here, we investigated the existence of an ERI to V1 fovea in macaque monkeys (male) while they performed spontaneous MSs, during fixation. We used voltage-sensitive dye imaging (VSDI) to measure and characterize at high spatiotemporal resolution the influence of MSs on neural population activity, in the foveal region of the primary visual cortex (V1). Microsaccades, performed over a blank screen, induced a two-phase response modulation: an early suppression followed by an enhancement. A correlation analysis revealed a widespread foveal increase in neural synchronization, peaking around ∼100 ms after MS onset. Next, we investigated the MS effects in the presence of a small visual stimulus and found that this modulation was different from the blank condition yet both modulations coexisted in the fovea. Finally, the VSD response to an external motion of the fixation point could not explain the MS modulation. These results support an ERI that may be involved in visual stabilization already at the level of V1.
我们的眼睛从未静止。即使当我们试图注视时，视觉凝视也绝非静止不动，因为我们会持续进行被称为注视性眼动的微小眼球运动。在注视阶段最快的眼动被称为微扫视（MSs），它会导致视觉输入的持续运动，主要影响中央凹中的神经元。然而我们的视觉看起来却是稳定的。为了解释这一差距，先前的研究表明存在一种进入视觉皮层的视网膜外输入（ERI），它可以解释这种运动并产生视觉稳定性。在这里，我们研究了猕猴（雄性）在注视过程中自发进行微扫视时，是否存在向V1中央凹的视网膜外输入。我们使用电压敏感染料成像（VSDI），以高时空分辨率测量并表征微扫视对初级视觉皮层（V1）中央凹区域神经群体活动的影响。在空白屏幕上进行的微扫视诱发了一种双相反应调制：早期抑制随后增强。相关性分析显示，神经同步在中央凹广泛增加，在微扫视开始后约100毫秒达到峰值。接下来，我们研究了在存在小视觉刺激的情况下微扫视的影响，发现这种调制与空白条件下不同，但两种调制在中央凹中共存。最后，对注视点外部运动的VSD反应无法解释微扫视调制。这些结果支持了一种视网膜外输入，它可能在V1水平就参与了视觉稳定。
