Following superior parietal lobule and intraparietal sulcus (SPL-IPS) damage, optic ataxia patients underestimate the distance of objects in the ataxic visual field such that they produce hypometric pointing errors. The metrics of these pointing errors relative to visual target eccentricity fit the cortical magnification of central vision. The SPL-IPS would therefore implement an active “peripheral magnification” to match the real metrics of the environment for accurate action. We further hypothesized that this active compensation of the central magnification by the SPL-IPS contributes to actual object’ size perception in peripheral vision. Three optic ataxia patients and 10 age-matched controls were assessed in comparing the thickness of two rectangles flashed simultaneously, one in central and another in peripheral vision. The bilateral optic ataxia patient exhibited exaggerated underestimation bias and uncertainty compared to the control group in both visual fields. The two unilateral optic ataxia patients exhibited a pathological asymmetry between visual fields: size perception performance was affected in their contralesional peripheral visual field compared to their healthy side. These results demonstrate that the SPL-IPS contributes to accurate size perception in peripheral vision.

在顶上小叶和顶内沟 (SPL-IPS) 损伤之后，视神经共济失调患者低估了共济失调视野中物体的距离，从而产生了偏斜指向错误。这些指向误差相对于视觉目标偏心率的度量符合中央视觉的皮层放大率。因此，SPL-IPS 将实施主动的“外围放大”，以匹配环境的真实指标，以实现准确的行动。我们进一步假设 SPL-IPS 对中央放大率的这种主动补偿有助于周边视觉中实际物体的尺寸感知。三名视神经共济失调患者和 10 名年龄匹配的对照者在比较两个同时闪烁的矩形的厚度时进行了评估，一个在中央，另一个在周边视觉。与对照组相比，双侧视神经共济失调患者在两个视野中都表现出夸大的低估偏差和不确定性。两名单侧视神经共济失调患者在视野之间表现出病理性不对称：与健康侧相比，其对侧周边视野的大小感知性能受到影响。这些结果表明 SPL-IPS 有助于周边视觉的准确尺寸感知。