Durmer J S, Rosenquist A C
Department of Neuroscience, University of Pennsylvania, Philadelphia 19104, USA.
Neuroscience. 2001;106(4):765-81. doi: 10.1016/s0306-4522(01)00321-9.
Cats rendered hemianopic by a unilateral visual cortical ablation can recover the visual orienting response in the hemianopic visual field following disruption of the caudal non-tectotectal containing half of the commissure of the superior colliculus. Ibotenic acid lesions of a small 'critical zone' in the contralateral substantia nigra result in a similar recovery effect. A conceptual framework developed by Wallace et al. (1990) [J. Comp. Neurol. 296, 222-252] proposed that elimination of contralateral substantia nigra 'critical zone' inhibition on the superior colliculus ipsilateral to a visual cortical lesion is responsible for the recovery. This model is insufficient, however, to explain the observation that hemi-decorticate cats with contralateral substantia nigra 'critical zone' lesions which include but extend beyond the 'critical zone' do not demonstrate the recovery. In these cats, subsequent transection of the commissure of the superior colliculus does lead to the recovery. We hypothesize that another projection through the caudal commissure of the superior colliculus, from the pedunculopontine nucleus, is involved in the recovery effect. Visual orienting behavior was recorded before and after ibotenic acid lesions made in the pedunculopontine nucleus region contralateral to a visual cortical ablation in 16 cats. Four cats with lesions in a small rostral region of the contralateral pedunculopontine nucleus recovered the visual orienting response in the previously hemianopic visual field. Contralateral tectal projections from the pedunculopontine nucleus are thought to be cholinergic and terminate as distinct patches in the intermediate gray layers of the superior colliculus. Since this region of the pedunculopontine nucleus also receives GABA-ergic afferents from the substantia nigra, we propose that a subcortical neural circuit including the substantia nigra, pedunculopontine nucleus, and superior colliculus is involved in the recovery of visual orienting.
通过单侧视觉皮层切除而导致偏盲的猫，在破坏上丘尾侧不含顶盖间连合的半侧连合后，能够恢复在偏盲视野中的视觉定向反应。在对侧黑质中一个小的“关键区”进行鹅膏蕈氨酸损伤会产生类似的恢复效果。华莱士等人（1990年）[《比较神经学杂志》296卷，222 - 252页]提出的一个概念框架认为，消除对侧黑质“关键区”对视觉皮层损伤同侧上丘的抑制作用是恢复的原因。然而，这个模型不足以解释这样的观察结果：即具有对侧黑质“关键区”损伤（包括但超出“关键区”）的半去皮质猫并没有表现出恢复。在这些猫中，随后切断上丘连合确实会导致恢复。我们假设，通过上丘尾侧连合从脚桥核发出的另一个投射参与了恢复效应。在16只猫中，对视觉皮层切除对侧的脚桥核区域进行鹅膏蕈氨酸损伤前后，记录了视觉定向行为。4只在对侧脚桥核小的嘴侧区域有损伤的猫在先前的偏盲视野中恢复了视觉定向反应。脚桥核的对侧顶盖投射被认为是胆碱能的，并以上丘中间灰质层中不同的斑块形式终止。由于脚桥核的这个区域也接受来自黑质的γ-氨基丁酸能传入纤维，我们提出一个包括黑质、脚桥核和上丘的皮层下神经回路参与了视觉定向的恢复。
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