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首页> 外文期刊>Journal of Computational Neuroscience >Dependence of Visual Cell Properties on Intracortical Synapses Among Hypercolumns: Analysis by a Computer Model
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Dependence of Visual Cell Properties on Intracortical Synapses Among Hypercolumns: Analysis by a Computer Model

机译：视觉细胞属性对超列之间的皮层内突触的依赖性：计算机模型的分析

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The role of intracortical synapses in affecting the property of visual cells is investigated by means of an original mathematical model of cortical circuitry in V1. The model represents a compromise between computational simplicity and physiological reliability. The model incorporates four different inputs into a cortical cell: thalamic input from the lateral geniculate nucleus, according to an even Gabor function; short-range inhibition confined within the hypercolumn; a long-range excitation, which emphasizes the properties of the input; and a long-range inhibition. In the model we assume that all cells receive a similar thalamic input, which differs simply according to its position in the retina and orientation preference. Simulations were performed, with different parameter values, to assess the main characteristics of cell response (i.e., the width and locations of subregions in the receptive field (RF), orientation tuning curve, and response to drifting and counterphase gratings) as a function of the strength and extension of intracortical excitatory synapses. Results suggest that, if intracortical excitation is confined within the hypercolumn, the cells exhibit the same properties as simple cells, both with regards to the width and shape of the RF, orientation tuning curve, and response to drifting and counterphase gratings. By contrast, if excitatory synapses extend beyond the hypercolumn with sufficient strength, the cells exhibit the typical characteristics of complex cells. A progressive shift from complex to simple cells can be realized with a monotonic variation in parameters. Simulations are also performed with a hierarchical model, to suggest possible experiments able to discriminate the present recurrent mechanism from the classical hierarchical one. Results support the assumptions of previous simpler models (Chance et al., 1999) and may help to understand and assess the role of intracortical synapses in rigorous quantitative terms.
机译：通过V1中皮层电路的原始数学模型，研究了皮层内突触在影响视觉细胞特性中的作用。该模型代表了计算简单性和生理可靠性之间的折衷。该模型将四个不同的输入合并到皮层细胞中：根据均匀的Gabor函数，来自外侧膝状核的丘脑输入；短程抑制局限于超柱内；远程激励，强调输入的属性；和远程抑制。在模型中，我们假设所有细胞都收到类似的丘脑输入，只是根据其在视网膜中的位置和方向偏好而不同。使用不同的参数值进行仿真，以评估细胞响应的主要特征（即，感受野（RF）中子区域的宽度和位置，方向调谐曲线以及对漂移和反相光栅的响应）皮质内兴奋性突触的强度和延伸。结果表明，如果皮质内激发被限制在超柱内，则细胞在射频的宽度和形状，方向调谐曲线以及对漂移和反相光栅的响应方面都表现出与简单细胞相同的特性。相反，如果兴奋性突触以足够的强度超出超柱，则细胞表现出复杂细胞的典型特征。通过参数的单调变化可以实现从复杂单元到简单单元的逐步转换。还使用分层模型执行模拟，以建议可能的实验，该实验能够将当前的递归机制与经典的分层机制区分开。结果支持以前较简单模型的假设（Chance等，1999），并可能有助于以严格的定量术语理解和评估皮层内突触的作用。

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