McCall M A, Tong L, Spear P D
Department of Psychology and Neurosciences Training Program, University of Wisconsin, Madison 53706.
Brain Res. 1988 Apr 26;447(1):67-78. doi: 10.1016/0006-8993(88)90966-3.
We studied the normal development of responses to visual stimulation among neurons in the posteromedial lateral suprasylvian (PMLS) visual cortex, an extrastriate visual cortical area in cats. Recordings were made from 495 single neurons in 19 kittens that were 2, 3, 4, 8, or 12 weeks of age, and the results were compared with those from normal adult cats. The percentage of neurons that respond to light increased from 57% in 2-week-old kittens to approximately adult values in 8-week-old kittens (81%). The strength and consistency of neuronal responses also increased with age. Nearly all of the responsive cells had well-defined excitatory receptive-field centers, and the receptive-field center sizes were similar to adults at all ages studied. However, few cells (5%) had inhibitory receptive-field surrounds in 2-week-old kittens. The incidence of surround inhibition increased to adult levels (about 40% of the cells) by 8 weeks of age, and the strength of surround inhibition also increased with age. Most cells responded best to moving stimuli in 2-week-old kittens, just as in adults. However, only about 20% of the responsive cells were direction sensitive at 2 weeks of age. The percentage of direction-sensitive cells increased gradually with age and reached approximately adult values by 8 weeks of age (74%). Once cells developed complete direction selectivity, with no response in the null direction, directional tuning width was similar to that in adults. When tested with slits of light flashed at various orientations or with spots and slits moving in various directions, few cells (8% or less) showed orientation selectivity at any age, just as in adults. Most of the cells were binocularly driven, and the ocular dominance distribution was similar to adults at all ages studied. These results indicate that many response properties of PMLS neurons are similar to those of adults as early as 2 weeks of age, soon after the time of eye opening. However, some properties show marked developmental changes. The mechanisms and sources of these changes are considered. In addition, the relevance of these results to mechanisms of compensation following early damage to visual cortical areas 17, 18 and 19 is discussed.
我们研究了猫的外侧上薛氏回后内侧（PMLS）视觉皮层（一个纹外视觉皮层区域）中神经元对视觉刺激反应的正常发育过程。对19只年龄分别为2周、3周、4周、8周或12周的小猫的495个单神经元进行了记录，并将结果与正常成年猫的结果进行了比较。对光有反应的神经元百分比从2周龄小猫的57%增加到8周龄小猫时接近成年水平（81%）。神经元反应的强度和一致性也随年龄增加。几乎所有有反应的细胞都有明确的兴奋性感受野中心，并且在所有研究年龄的感受野中心大小都与成年猫相似。然而，在2周龄小猫中，很少有细胞（5%）有抑制性感受野周边。到8周龄时，周边抑制的发生率增加到成年水平（约40%的细胞），并且周边抑制的强度也随年龄增加。在2周龄小猫中，大多数细胞对移动刺激反应最佳，这与成年猫一样。然而，在2周龄时，只有约20%有反应的细胞对方向敏感。对方向敏感的细胞百分比随年龄逐渐增加，到8周龄时达到接近成年水平（74%）。一旦细胞发展出完全的方向选择性，在零方向无反应时，方向调谐宽度与成年猫相似。当用不同方向闪烁的光缝或用在不同方向移动的光点和光缝进行测试时，在任何年龄，很少有细胞（8%或更少）表现出方向选择性，这与成年猫一样。大多数细胞由双眼驱动，并且在所有研究年龄的眼优势分布都与成年猫相似。这些结果表明，早在睁眼后不久的2周龄时，PMLS神经元的许多反应特性就与成年猫相似。然而，一些特性显示出明显的发育变化。本文考虑了这些变化的机制和来源。此外，还讨论了这些结果与早期视觉皮层17、18和19区损伤后补偿机制的相关性。
