EFFECT OF THE RICHNESS OF THE ENVIRONMENT ON NEURONS IN CAT VISUAL-CORTEX .1. RECEPTIVE-FIELD PROPERTIES
EFFECT OF THE RICHNESS OF THE ENVIRONMENT ON NEURONS IN CAT VISUAL-CORTEX .1. RECEPTIVE-FIELD PROPERTIES
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DOI：
10.1016/0165-3806(90)90125-i
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发表时间：
1990-04-01
期刊：
影响因子：
--
通讯作者：
CYNADER, M
中科院分区：
文献类型：
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作者：
BEAULIEU, C;CYNADER, M
最近的一项研究表明，与在贫瘠环境中饲养的猫相比，在丰富环境条件下饲养的猫的视觉皮质中与扁平小泡(FS突触)相关的突触接触数量更多。此外，FS突触接触的大小还受到发育过程中S环境的丰富程度的影响。有证据表明，绝大多数FS突触是GABA能的(γ-氨基丁酸)，并且视皮层神经元的许多特性受到GABA依赖机制的影响，因此有人认为，环境的丰富引起的这些形态突触的变化与皮质感受野特性的差异有关。在本研究中，通过记录视皮层含有较高比例的定向选择性细胞和较低比例的定向偏向和无定向细胞来探索这一点。此外，EC动物的定向调谐明显更尖锐(反应单位的平均带宽等于32度)。高于IC猫(平均带宽等于38度；P<；0.001)。这主要是由于贫困皮质中定向偏向单位的发生率较高(EC组为23%，IC组为41%；P<；0.01)。环境的丰富性对单位的响应度有很大影响。我们发现，EC皮层的所有单位都对光刺激有反应。相比之下，被研究的贫困细胞中有14%未能将其反应提高到自发活动标准差的至少两倍，因此被判定为无反应。我们认为，IC视觉单位的低响应性与每个IC神经元的GABA能突触数量的增加有关，而IC皮质的选择性更大可能是由于GABA能抑制连接的分布更加广泛。
In a recent study, it was demonstrated that the number of synaptic contacts associated with flat vesicles (FS synapses) is higher in the visual cortex of cats raised in an enriched environmental condition (EC) compared to those reared in an impoverished condition (IC). Moreover, the size of the FS synaptic contacts is also affected by the richness of the animal''s environment during development. Based on evidence that the vast majority of FS synapses are GABAergic (.gamma.-aminobutyric acid) and that many of the properties of visual cortex neurons are influenced by GABA-dependent mechanisms, it has been suggested that these morphological synaptic changes induced by the richness of the environment correlate with differences in cortical receptive field properties. In the present study, this has been explored by recording visual cortex contains a higher proportion of orientation selective cells and a lower proportion of orientation biased and unoriented cells. In addition, orientation tuning is significantly sharper in EC animals (mean bandwidth of responsive units is equal to 32.degree.) than in IC cats (mean bandwidth is equal to 38.degree.; P < 0.001). This is mostly due to the greater incidence of orientation biased units in impoverished cortex (23% in EC and 41% in IC animals; P < 0.01). Unit responsivity is significantly affected by the richness of the environment. We found that all units of the EC cortex were responsive to light stimuli. In contrast, 14% of the impoverished cells studied fail to increase their response to at least twice the standard deviation of the spontaneous activity and were judged as unresponsive. We suggest that the lower responsivity in IC visual units is related to the higher number of GABAergic synapses per IC neuron, while the broader selectivity in IC cortex might be due to a more diffuse distribution of the GABAergic inhibitory connections.