Fig. 8.

Sources of variability in the LGMD model. The model was run with specific sources of variability eliminated. “Full” (F) refers to the model with all sources of variability. Other conditions eliminate variability in excitatory synaptic maximum conductance (F-Exc Gmax), excitatory synaptic timing (F-Exc Jitter), both excitatory timing and conductance variability (F-Exc Var), the inhibitory variability (F-Inh Var), and all visually driven variability (spontaneous only). Variability was estimated for groups of 50 simulated approaches and averaged over 10 groups. A: the relative SNR_peak resulting from elimination of sources of variability. The height of each bar shows the difference from the full condition, normalized by the difference between full and spontaneous only. The SNR_peak (averaged over l/|v|) values of the full condition are 14.0 and 9.9 for V_m and IFR, respectively, whereas the SNR_peak values for the spontaneous-only condition are 19.0 and 14.0. B: the proportion that the SD_{peak time} value is decreased from that of the full condition for each condition shown. Bar height indicates the difference from full model SD_{peak time} for each condition, divided by the full model SD_{peak time} value (SD_full − SD_condition)/SD_full. SD_{peak time} values for the full model were 38.8 and 45.5 ms for V_m and IFR, respectively (averaged over all 3 l/|v| values).