Wright J J, Alexander D M, Bourke P D
Liggins Institute, University of Auckland, Auckland, New Zealand.
Vision Res. 2006 Sep;46(17):2703-20. doi: 10.1016/j.visres.2006.02.017. Epub 2006 Apr 5.
We propose a model of self-organization of synaptic connections in V1, emphasizing lateral interactions. Subject to Hebbian learning with decay, evolution of synaptic strengths proceeds to a stable state in which all synapses are either saturated, or have minimum pre/post-synaptic coincidence. The most stable configuration gives rise to anatomically realistic "local maps", each of macro-columnar size, and each organized as Mobius projections of retinotopic space. A tiling of V1, constructed of approximately mirror-image reflections of each local map by its neighbors is formed, accounting for orientation-preference singularities, linear zones, and saddle points-with each map linked by connections between sites of common orientation preference. Ocular dominance columns are partly explained as a special case of the same process. The occurrence of direction preference fractures always in odd numbers around singularities is a specific feature explained by the Mobius configuration of the local map. Effects of stimulus velocity, orientation relative to direction of motion, and extension, upon orientation preference, which are not accounted for by spatial filtering, are explained by interactions between the classic receptive field and global V1.
我们提出了一种V1区突触连接的自组织模型，强调横向相互作用。在具有衰减的赫布学习规则下，突触强度的演化会达到一个稳定状态，即所有突触要么饱和，要么突触前/后重合度最小。最稳定的构型会产生解剖学上逼真的“局部图谱”，每个图谱具有宏观柱状大小，并且每个图谱都被组织成视网膜拓扑空间的莫比乌斯投影。由每个局部图谱与其相邻图谱的近似镜像反射构成的V1区镶嵌图形成，这解释了方向偏好奇点、线性区域和鞍点——每个图谱通过具有共同方向偏好的位点之间的连接相连。眼优势柱部分地被解释为同一过程的特殊情况。在奇点周围方向偏好断裂总是以奇数出现这一特定特征，由局部图谱的莫比乌斯构型来解释。刺激速度、相对于运动方向的方向以及伸展对方向偏好的影响（这些影响无法通过空间滤波来解释），由经典感受野与全局V1区之间的相互作用来解释。
