Shirazi Mehdi N
Osaka Institute of Technology, Faculty of Information Science 1-79-1, Kitayama, Hirakata-shi, Osaka, 573-0196, Japan.
Biol Cybern. 2004 Aug;91(2):115-30. doi: 10.1007/s00422-004-0483-5. Epub 2004 Aug 31.
The recent consensus is that virtually all aspects of response selectivity exhibited by the primary visual cortex are either created or sharpened by cortical inhibitory interneurons. Experimental studies have shown that there are cortical inhibitory cells that are driven by geniculate cells and that, like their cortical excitatory counterparts, are orientation selective, though less sharply tuned. The main goal of this article is to demonstrate how orientation-selective inhibition might be created by the circuitry of the primary visual cortex (striate cortex, V1) from its nonoriented geniculate inputs. To fulfill this goal, first, a Bayes-Markov computational model is developed for the V1 area dedicated to foveal vision. The developed model consists of three parts: (i) a two-layered hierarchical Markov random field that is assumed to generate the activity patterns of the geniculate and cortical inhibitory cells, (ii) a Bayesian computational goal that is formulated based on the maximum a posteriori (MAP) estimation principle, and (iii) an iterative, deterministic, parallel algorithm that leads the cortical circuitry to achieve its assigned computational goal. The developed model is not fully LGN driven and it is not implementable by the neural machinery of V1. The model, then, is transformed into a fully LGN-driven and physiologically plausible form. Computer simulation is used to demonstrate the performance of the developed models.
最近的共识是，初级视觉皮层所表现出的反应选择性的几乎所有方面都是由皮层抑制性中间神经元产生或增强的。实验研究表明，存在由膝状细胞驱动的皮层抑制性细胞，并且与它们的皮层兴奋性对应细胞一样，具有方向选择性，尽管调谐不太尖锐。本文的主要目标是展示初级视觉皮层（纹状皮层，V1）的电路如何从其无方向的膝状输入中产生方向选择性抑制。为了实现这一目标，首先，为专门用于中央凹视觉的V1区域开发了一个贝叶斯 - 马尔可夫计算模型。所开发的模型由三部分组成：（i）一个两层分层马尔可夫随机场，假定其生成膝状细胞和皮层抑制性细胞的活动模式；（ii）基于最大后验（MAP）估计原则制定的贝叶斯计算目标；（iii）一种迭代、确定性、并行算法，引导皮层电路实现其指定的计算目标。所开发的模型并非完全由外侧膝状体驱动，并且V1的神经机制无法实现该模型。然后，将该模型转换为完全由外侧膝状体驱动且在生理上合理的形式。使用计算机模拟来展示所开发模型的性能。
