Elliott T, Shadbolt N R
Department of Psychology, University of Nottingham, Nottingham, NG7 2RD, United Kingdom.
J Neurosci. 1998 Aug 1;18(15):5850-8. doi: 10.1523/JNEUROSCI.18-15-05850.1998.
Activity-dependent competition between afferents in the primary visual cortex of many mammals is a quintessential feature of neuronal development. From both experimental and theoretical perspectives, understanding the mechanisms underlying competition is a significant challenge. Recent experimental work suggests that geniculocortical afferents might compete for retrograde neurotrophic factors. We show that a mathematically well-characterized model of retrograde neurotrophic interactions, in which the afferent uptake of neurotrophic factors is activity-dependent and in which the average level of uptake determines the complexity of the axonal arbors of afferents, permits the anatomical segregation of geniculocortical afferents into ocular dominance columns. The model induces segregation provided that the levels of neurotrophic factors available either by activity-independent release from cortical cells or by exogenous cortical infusion are not too high; otherwise segregation breaks down. We show that the model exhibits changes in ocular dominance column periodicity in response to changes in interocular image correlations and that the model predicts that changes in intraocular image correlations should also affect columnar periodicity.
许多哺乳动物初级视觉皮层中传入神经元之间的活动依赖性竞争是神经元发育的一个典型特征。从实验和理论两个角度来看，理解竞争背后的机制都是一项重大挑战。最近的实验工作表明，膝状体皮质传入神经元可能会竞争逆行神经营养因子。我们表明，一个在数学上有充分特征描述的逆行神经营养相互作用模型，其中神经营养因子的传入摄取是活动依赖性的，并且摄取的平均水平决定了传入神经元轴突分支的复杂性，该模型允许膝状体皮质传入神经元在解剖学上分离成眼优势柱。只要通过皮质细胞的非活动依赖性释放或通过外源性皮质注入可获得的神经营养因子水平不太高，该模型就会诱导分离；否则分离就会瓦解。我们表明，该模型会响应两眼间图像相关性的变化而表现出眼优势柱周期性的变化，并且该模型预测眼内图像相关性的变化也应该影响柱状周期性。
