Department of Psychological Medicine, University of Auckland, Auckland, New Zealand,
Cogn Neurodyn. 2008 Jun;2(2):147-57. doi: 10.1007/s11571-008-9048-y. Epub 2008 Apr 19.
A model of self-organization of synapses in the striate cortex is described, and its functional implications discussed. Principal assumptions are: (a) covariance of cell firing declines with distance in cortex, (b) covariance of stimulus characteristics declines with distance in the visual field, and (c) metabolic rates are approximately uniform in all small axonal segments. Under these constraints, Hebbian learning implies a maximally stable synaptic configuration corresponding to anatomically and physiologically realistic ''local maps'', each of macro-columnar size, and each organized as Möbius projections of a "global map" of retinotopic form. Convergence to the maximally stable configuration is facilitated by the spatio-temporal learning rule. A tiling of V1, constructed of approximately mirror-image reflections of each local map by its neighbors, is formed. The model supplements standard concepts of feed-forward visual processing by introducing a new basis for contextual modulation and neural network identifications of visual signals, as perturbation of the synaptic configuration by rapid stimulus transients. On a long time-scale, synaptic development could overwrite the Möbius configuration, while LTP and LTD could mediate synaptic gain on intermediate time-scales.
描述了纹状皮层中突触的自组织模型，并讨论了其功能意义。主要假设是：(a)细胞放电的协方差随皮层距离的增加而降低，(b)刺激特征的协方差随视野距离的增加而降低，(c)代谢率在所有小轴突段基本均匀。在这些约束下，赫布学习意味着与解剖学和生理学上现实的“局部图”相对应的最大稳定突触配置，每个局部图的大小与宏观柱状大小相当，并且每个局部图都组织成视域形式的“全局图”的莫比乌斯投影。时空学习规则促进了向最大稳定配置的收敛。通过其相邻局部图的镜像反射构建了 V1 的平铺。该模型通过引入快速刺激瞬变对突触配置的干扰，为上下文调制和神经网络对视觉信号的识别提供了新的基础，从而补充了标准的前馈视觉处理概念。在长时间尺度上，突触发育可以覆盖莫比乌斯配置，而 LTP 和 LTD 可以在中间时间尺度上调节突触增益。
