Flaum Eye Institute, University of Rochester, Rochester, NY, USA.
Medical Scientist Training Program, University of Rochester, Rochester, NY, USA.
Brain. 2020 Jun 1;143(6):1857-1872. doi: 10.1093/brain/awaa128.
Stroke damage to the primary visual cortex (V1) causes a loss of vision known as hemianopia or cortically-induced blindness. While perimetric visual field improvements can occur spontaneously in the first few months post-stroke, by 6 months post-stroke, the deficit is considered chronic and permanent. Despite evidence from sensorimotor stroke showing that early injury responses heighten neuroplastic potential, to date, visual rehabilitation research has focused on patients with chronic cortically-induced blindness. Consequently, little is known about the functional properties of the post-stroke visual system in the subacute period, nor do we know if these properties can be harnessed to enhance visual recovery. Here, for the first time, we show that 'conscious' visual discrimination abilities are often preserved inside subacute, perimetrically-defined blind fields, but they disappear by ∼6 months post-stroke. Complementing this discovery, we now show that training initiated subacutely can recover global motion discrimination and integration, as well as luminance detection perimetry, just as it does in chronic cortically-induced blindness. However, subacute recovery was attained six times faster; it also generalized to deeper, untrained regions of the blind field, and to other (untrained) aspects of motion perception, preventing their degradation upon reaching the chronic period. In contrast, untrained subacutes exhibited spontaneous improvements in luminance detection perimetry, but spontaneous recovery of motion discriminations was never observed. Thus, in cortically-induced blindness, the early post-stroke period appears characterized by gradual-rather than sudden-loss of visual processing. Subacute training stops this degradation, and is far more efficient at eliciting recovery than identical training in the chronic period. Finally, spontaneous visual improvements in subacutes were restricted to luminance detection; discrimination abilities only recovered following deliberate training. Our findings suggest that after V1 damage, rather than waiting for vision to stabilize, early training interventions may be key to maximize the system's potential for recovery.
中风对初级视皮层（V1）的损伤导致失明，称为偏盲或皮质诱导性失明。虽然在中风后最初的几个月内可能会自发出现周边视野改善，但在中风后 6 个月时，这种缺陷被认为是慢性和永久性的。尽管来自感觉运动性中风的证据表明，早期损伤反应会增强神经可塑性潜力，但迄今为止，视觉康复研究一直集中在慢性皮质诱导性失明的患者身上。因此，对于中风后视觉系统在亚急性期的功能特性知之甚少，也不知道是否可以利用这些特性来增强视觉恢复。在这里，我们首次表明，“有意识”的视觉辨别能力通常在亚急性、周边定义的盲区内保留，但在中风后 6 个月左右消失。作为这一发现的补充，我们现在表明，在亚急性阶段开始的训练可以恢复全局运动辨别和整合，以及亮度检测视野，就像在慢性皮质诱导性失明中一样。然而，亚急性恢复的速度快了六倍；它还可以推广到盲区内更深、未经训练的区域，以及运动感知的其他（未经训练）方面，防止它们在进入慢性期后退化。相比之下，未经训练的亚急性患者在亮度检测视野中表现出自发改善，但从未观察到运动辨别能力的自发恢复。因此，在皮质诱导性失明中，中风后早期阶段的视觉处理似乎是逐渐而不是突然丧失的。亚急性训练阻止了这种退化，并且比慢性期的相同训练更有效地引发恢复。最后，亚急性自发的视觉改善仅限于亮度检测；只有经过刻意训练，辨别能力才会恢复。我们的发现表明，在 V1 损伤后，与其等待视力稳定，早期的训练干预可能是最大限度地发挥系统恢复潜力的关键。
