Institute of Gerontology, Wayne State University, Detroit, USA.
Hobart and William Smith Colleges, Geneva, NY, USA; Flaum Eye Institute, University of Rochester, Rochester, NY, USA.
Neuropsychologia. 2015 Feb;68:82-93. doi: 10.1016/j.neuropsychologia.2015.01.003. Epub 2015 Jan 7.
Partial cortical blindness is a visual deficit caused by unilateral damage to the primary visual cortex, a condition previously considered beyond hopes of rehabilitation. However, recent data demonstrate that patients may recover both simple and global motion discrimination following intensive training in their blind field. The present experiments characterized motion-induced neural activity of cortically blind (CB) subjects prior to the onset of visual rehabilitation. This was done to provide information about visual processing capabilities available to mediate training-induced visual improvements. Visual Evoked Potentials (VEPs) were recorded from two experimental groups consisting of 9 CB subjects and 9 age-matched, visually-intact controls. VEPs were collected following lateralized stimulus presentation to each of the 4 visual field quadrants. VEP waveforms were examined for both stimulus-onset (SO) and motion-onset (MO) related components in postero-lateral electrodes. While stimulus presentation to intact regions of the visual field elicited normal SO-P1, SO-N1, SO-P2 and MO-N2 amplitudes and latencies in contralateral brain regions of CB subjects, these components were not observed contralateral to stimulus presentation in blind quadrants of the visual field. In damaged brain hemispheres, SO-VEPs were only recorded following stimulus presentation to intact visual field quadrants, via inter-hemispheric transfer. MO-VEPs were only recorded from damaged left brain hemispheres, possibly reflecting a native left/right asymmetry in inter-hemispheric connections. The present findings suggest that damaged brain hemispheres contain areas capable of responding to visual stimulation. However, in the absence of training or rehabilitation, these areas only generate detectable VEPs in response to stimulation of the intact hemifield of vision.
部分皮质盲是一种由初级视皮层单侧损伤引起的视觉缺陷，这种情况以前被认为是无法康复的。然而，最近的数据表明，患者在其盲区内进行密集训练后，可能会恢复对简单和全局运动的辨别能力。本实验在视觉康复开始之前，对皮质盲（CB）患者的运动诱导神经活动进行了特征描述。这是为了提供有关介导训练诱导视觉改善的可用视觉处理能力的信息。从由 9 名 CB 受试者和 9 名年龄匹配的视觉正常对照组组成的两个实验组中记录视觉诱发电位（VEPs）。向每个 4 个视野象限的外侧化刺激呈现后，收集 VEPs。在后外侧电极中检查了 VEP 波形，以获得刺激起始（SO）和运动起始（MO）相关成分。虽然刺激呈现给 CB 受试者的完整视野区域会在大脑对侧区域诱发出正常的 SO-P1、SO-N1、SO-P2 和 MO-N2 幅度和潜伏期，但在视野盲区内没有观察到这些成分。在受损的大脑半球中，仅在刺激呈现给完整的视野象限时，通过半球间转移，才会记录到 SO-VEPs。MO-VEPs 仅从受损的左大脑半球记录，这可能反映了半球间连接的固有左右不对称性。本研究结果表明，受损的大脑半球包含能够对视觉刺激做出反应的区域。然而，在没有训练或康复的情况下，这些区域仅在对完整视野半球的刺激做出反应时才会产生可检测到的 VEPs。
