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Fig. 13.8. Quantifying the spatial relationship between two receptive fields. For each pair of neurons connected with excitatory lateral connections, the afferent connection weights were examined to determine (1) the orientation preference of the neuron (shown as oriented bars), and (2) the location of the receptive field in retinal space (as the center of gravity of the afferent weight matrix). From these values, the direction &phi, radial distance &delta, and difference between orientation preferences &theta between all pairs of neurons were calculated. Notice that these values define the spatial relationship between the two neurons in the retinal (or visual) space, not in the cortical space, and therefore allow comparing connectivity with edge-cooccurrence data. Such a comparison is presented in Figure 13.9. Adapted from Geisler et al. (2001).