Figure 1.

Retinotectal circuit model. A, Structure of the neural circuit in the retinotectal circuit model. The model contains 185 RGCs, 37 INs, and 37 TNs. The RGCs have excitatory projections to both the TNs and the INs. Each IN has an inhibitory projection to the TN, which receives excitation from the same RGCs as each IN does. TNs have excitatory projections to neighboring TNs. Open circles represent excitatory synapses, which are modified through STDP, and filled circles represent excitatory synapses, which are fixed and not modified through STDP. Filled square represents an inhibitory synapse, which is fixed and not modified through STDP. B, Temporally asymmetric learning window reproduced using a simple STDP model that is included in the synapses from RGCs to TNs. A detailed description of the simple STDP model is provided in the supplemental material (available at www.jneurosci.org). C, D, Time profiles of the model responses to a fast-moving bar (0.3 μm/ms) before training. C, Light amplitude at the center of the receptive field of the RGC indicated by the arrow in A and firing rates of the RGC, the IN located in the center of the tectum, and the TN located in the center of the tectum, as indicated in A. D, Inputs to the TN located in the center of the tectum from the RGCs, IN, and neighboring TNs and the summation of these three inputs (total input), as indicated.