Jenks Samantha K, Carrasco Marisa, Poletti Martina
Department of Brain and Cognitive Sciences, University of Rochester, Rochester, NY, 14627, USA.
Center for Visual Science, University of Rochester, Rochester, NY, 14627, USA.
J Neurosci. 2025 Jul 22. doi: 10.1523/JNEUROSCI.0055-25.2025.
Visual perception is characterized by known asymmetries in the visual field; human's visual sensitivity is higher along the horizontal than the vertical meridian, and along the lower than the upper vertical meridian. These asymmetries decrease with decreasing eccentricity from the periphery to the center of gaze, suggesting that they may be absent in the 1-deg foveola, the retinal region used to explore scenes at high-resolution. Using high-precision eyetracking and gaze-contingent display, allowing for accurate control over the stimulated foveolar location despite the continuous eye motion at fixation, we investigated fine visual discrimination at different isoeccentric locations across the foveola and parafovea in 12 human observers (both sexes). Although the tested foveolar locations were only 0.3 deg away from the center of gaze, we show that, similar to more eccentric locations, humans are more sensitive to stimuli presented along the horizontal than the vertical meridian. Whereas the magnitude of this asymmetry is reduced in the foveola, the magnitude of the vertical meridian asymmetry is comparable but, interestingly, the asymmetry is reversed: stimuli presented slightly above the center of gaze are more easily discerned than when presented at the same eccentricity below the center of gaze. Therefore, far from being uniform, as often assumed, foveolar vision is characterized by perceptual asymmetries. Further, these asymmetries differ not only in magnitude but also in direction compared to those present just ∼4deg away from the center of gaze, resulting in overall different foveal and extrafoveal perceptual fields. The 1-degree foveola, the retinal region responsible for high-resolution vision, has traditionally been studied as a uniform unit. Our research challenges this notion by uncovering perceptual asymmetries in foveolar fine spatial vision. Using a high-resolution eyetracker, we demonstrate that humans discriminate objects above the center of gaze better than below, a pattern opposite to the asymmetries observed just a few degrees away from the foveola. These findings reveal not only that this region is not uniform but also that it is not simply a high-resolution extension of extrafoveal vision but it is characterized by unique features. The discovery of these perceptual asymmetries raises critical questions about the neural representation of foveal input and the underlying factors shaping these differences.
视觉感知的特点是视野中存在已知的不对称性；人类的视觉敏感度在水平子午线上高于垂直子午线，在垂直子午线下半部分高于上半部分。随着从周边向注视中心的离心率降低，这些不对称性会减小，这表明在1度的中央凹小窝（用于高分辨率探索场景的视网膜区域）中可能不存在这些不对称性。我们使用高精度眼动追踪和注视点相关显示，尽管在注视时眼睛持续运动，但仍能精确控制刺激的中央凹小窝位置，对12名人类观察者（男女皆有）的中央凹小窝和旁中央凹不同等离心率位置的精细视觉辨别进行了研究。尽管测试的中央凹小窝位置距离注视中心仅0.3度，但我们发现，与更偏心的位置类似，人类对沿水平子午线呈现的刺激比对沿垂直子午线呈现的刺激更敏感。虽然这种不对称性的程度在中央凹小窝中有所降低，但垂直子午线不对称性的程度相当，但有趣的是，不对称性发生了反转：在注视中心上方稍高位置呈现的刺激比在注视中心下方相同离心率位置呈现的刺激更容易辨别。因此，中央凹小窝视觉远非通常所认为的那样均匀，而是具有感知不对称性。此外，与距离注视中心仅约4度处的不对称性相比，这些不对称性不仅在程度上不同，而且在方向上也不同，从而导致整体上不同的中央凹和中央凹外感知场。1度的中央凹小窝是负责高分辨率视觉的视网膜区域，传统上一直被作为一个均匀的单元进行研究。我们的研究通过揭示中央凹小窝精细空间视觉中的感知不对称性，对这一概念提出了挑战。使用高分辨率眼动追踪仪，我们证明人类对注视中心上方的物体辨别能力优于下方，这一模式与在距离中央凹小窝仅几度处观察到的不对称性相反。这些发现不仅揭示了该区域并非均匀，而且还表明它不仅仅是中央凹外视觉的高分辨率扩展，而是具有独特的特征。这些感知不对称性的发现引发了关于中央凹输入的神经表征以及塑造这些差异的潜在因素的关键问题。
