Schmid L M, Rosa M G, Calford M B, Ambler J S
Department of Physiology and Pharmacology, University of Queensland, Australia 4072.
Cereb Cortex. 1996 May-Jun;6(3):388-405. doi: 10.1093/cercor/6.3.388.
The effect of discrete monocular retinal lesions on the representation of the visual field in the primary visual area (V1) was investigated in adult cats. Lesions were created using argon lasers, 8 d to 4(1/2) months prior to electrophysiological recording. This produced lesion projection zones (LPZs) in V1, 1.6-9.5 mm wide, that were deprived of their normal input from one eye, but that received a normal input from the other eye. Nevertheless, at the majority of recording sites within these zones neuronal responses were elicited by stimulation of the lesioned eye, with receptive fields being displaced onto regions of retina surrounding the lesion, while receptive fields determined through stimulation of the normal eye followed the normal visuotopic organization of V1. However, neuronal responses to stimulation of the lesioned eye within the LPZs were characterized by rapid habituation and unusually low firing rates in comparison with responses to stimulation of the normal eye. Stimulation of the normal eye temporarily marked the responsiveness of neurons within the LPZ to stimulation of the lesioned eye. The proportion of neurons responsive to stimulation of the lesioned eye was higher just inside the borders of the LPZs than at the centers of these zones. However, neurons responsive to stimulation of the test eye were found up to 3.6 mm from the perimeter of the LPZs, and therefore the shifts in the visuotopic map caused by retinal lesions cannot be explained solely on the basis of the normal scatter of receptive fields and point-image size in V1. The proportion of cells responsive to stimulation of the lesioned eye was highest in the infragranular layers, and lowest in the supragranular layers. By combining a restricted lesion of one eye with laser photocoagulation of the optic disc of the other eye, the effects of the normal eye on the lesion-induced visuotopic reorganization were also investigated. Neither chronic nor acute deactivation produced any discernible further changes in visuotopy or in the characteristics of neuronal responses to stimulation of the eye with the discrete lesions. Our findings show that the representations of the two eyes in adult visual cortex are capable of independent reorganization. These findings parallel those of work in auditory cortex, suggesting that topographic reorganization in primary sensory areas of adult cortex may be governed by similar mechanisms.
在成年猫中研究了离散性单眼视网膜损伤对初级视觉区（V1）视野表征的影响。在进行电生理记录前8天至4个半月，使用氩激光造成损伤。这在V1中产生了损伤投射区（LPZ），其宽度为1.6 - 9.5毫米，该区域失去了来自一只眼睛的正常输入，但从另一只眼睛接收正常输入。然而，在这些区域内的大多数记录位点，通过刺激损伤眼可引发神经元反应，感受野被移位到损伤周围的视网膜区域，而通过刺激正常眼确定的感受野则遵循V1的正常视拓扑组织。但是，与对正常眼刺激的反应相比，LPZ内对损伤眼刺激的神经元反应具有快速习惯化和异常低的放电率的特征。刺激正常眼暂时标记了LPZ内神经元对损伤眼刺激的反应性。对损伤眼刺激有反应的神经元比例在LPZ边界内侧比在这些区域的中心更高。然而，在距LPZ周边3.6毫米处发现了对测试眼刺激有反应的神经元，因此视网膜损伤引起的视拓扑图变化不能仅基于V1中感受野的正常散布和点图像大小来解释。对损伤眼刺激有反应的细胞比例在颗粒下层最高，在颗粒上层最低。通过将一只眼睛的局限性损伤与另一只眼睛的视盘激光光凝相结合，还研究了正常眼对损伤诱导的视拓扑重组的影响。无论是慢性还是急性失活，在视拓扑或对有离散损伤眼刺激的神经元反应特征方面均未产生任何可察觉的进一步变化。我们的研究结果表明，成年视觉皮层中两只眼睛的表征能够独立重组。这些发现与听觉皮层的研究结果相似，表明成年皮层初级感觉区域的拓扑重组可能受类似机制支配。
