Figure 1.

Schematic of the model of the visual motion pathway of the blowfly and the various modules from which it is composed. The basic modules are labeled by white capsules; their elaborated counterparts are labeled by gray capsules. a, Impulse response of the low-pass filter approximating the dynamical properties of the photoreceptors. b, Impulse response of the LMC/photoreceptor linear filter. c, Basic correlation-type motion detector. d, High-pass filter elaboration of the motion detector. e, The weight field of the local sensitivity distribution of the right model HSE (contour plot in cylindrical projection; brighter areas indicate greater sensitivities) is the same for all model variations; the frontal equatorial viewing direction is at 0° azimuth and elevation, and the left HSE is mirror symmetric. f, Linear dendritic summation of positive and negative detector output. g, Circuit representation of the passive membrane model. g₀, Leak conductance of the pooling neuron; g_e and g_i, excitatory and inhibitory synaptic conductances driven by the output of the multiplication after rectification; E₀, E_e, and E_i, corresponding reversal potentials. The model referred to here as the “basic model” is composed of the components a, c, e, and f. The most elaborated version, composed from b, d, e, and g, can be parameterized to fit the neuronal data best. lp, First-order linear low-pass filter; M, algebraic multiplication; hp, first-order high-pass filter.