Bartsch A P, van Hemmen J L
Physik Department T35, Technische Universität München, Germany.
Biol Cybern. 2001 Jan;84(1):41-55. doi: 10.1007/s004220170003.
We present a network model of visual map development in layer 4 of primary visual cortex. Our model comprises excitatory and inhibitory spiking neurons. The input to the network consists of correlated spike trains to mimick the activity of neurons in the lateral geniculate nucleus (LGN). An activity-driven Hebbian learning mechanism governs the development of both the network's lateral connectivity and feedforward projections from LGN to cortex. Plasticity of inhibitory synapses has been included into the model so as to control overall cortical activity. Even without feedforward input, Hebbian modification of the excitatory lateral connections can lead to the development of an intracortical orientation map. We have found that such an intracortical map can guide the development of feedforward connections from LGN to cortical simple cells so that the structure of the final feedforward orientation map is predetermined by the intracortical map. In a scenario in which left- and right-eye geniculocortical inputs develop sequentially one after the other, the resulting maps are therefore very similar, provided the intracortical connectivity remains unaltered. This may explain the outcome of so-called reverse lid-suture experiments, where animals are reared so that both eyes never receive input at the same time, but the orientation maps measured separately for the two eyes are nevertheless nearly identical.
我们提出了一个初级视觉皮层第4层视觉图谱发育的网络模型。我们的模型由兴奋性和抑制性脉冲神经元组成。网络的输入由相关的脉冲序列组成，以模拟外侧膝状体核（LGN）中神经元的活动。一种活动驱动的赫布学习机制控制着网络的横向连接以及从LGN到皮层的前馈投射的发育。抑制性突触的可塑性已被纳入模型，以控制皮层的整体活动。即使没有前馈输入，兴奋性横向连接的赫布修饰也能导致皮层内方向图谱的发育。我们发现，这样的皮层内图谱可以指导从LGN到皮层简单细胞的前馈连接的发育，从而使最终的前馈方向图谱的结构由皮层内图谱预先确定。在一种左右眼膝状体皮层输入依次相继发育的情况下，因此只要皮层内连接保持不变，所产生的图谱就非常相似。这可能解释了所谓的反向眼睑缝合实验的结果，在该实验中，动物饲养过程中两只眼睛从未同时接受输入，但分别测量的两只眼睛的方向图谱却几乎相同。
