Fig 14. Summary of key results on different effects of triadic and axonal inhibition on relay-cell (RC) response.

(A) Dependence of diameter of RC receptive-field center $d_{\text{c}}^{\text{R}}$ on two key model parameters (w_GIp, weight of proximal excitation of the interneuron (IN); w_IRa, weight of axonal inhibition) for the case of axonal inhibition only (i.e., w_IRt = 0). For this example the diameter of the ganglion-cell receptive-field center $d_{\text{c}}^{\text{G}}$ is fixed to 1.8 deg, and the retinogeniculate excitation is set to w_GR = 11.6 nS. (B) Transient and sustained RC responses for center-filling spots, corresponding to maximal responses in the area-response curves, for the cases of only triadic or only axonal inhibition. Dependence of maximal response on retinogeniculate excitation weight w_GR is depicted. Other parameters: w_IRa = 4 nS, w_GIp = 0.6 nS. (C) Dependence of center-surround antagonism, quantified by the coefficient α_RC (Eq 7), on w_GIp, the weight of the GC excitation of INs on the proximal dendrites. Dark-blue line: No inhibition, w_IRa = w_IRt = 0. Red line: Axonal inhibition only, w_IRt = 0, w_IRa = 8 nS. Green line: Triadic inhibition only, w_IRa = 0. Light-blue line: Both triadic and axonal inhibition, w_IRa = 8 nS. Retinogeniculate excitation is set to w_GR = 15.6 nS. In B and C simulation data points are marked with dots, and lines are added as a guide for the eye. Note that 500 trials, not the default value of 10 trials, were used to compute the depicted trial-averaged spike-count rate in panel B.