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Fig. 11.7. Distribution of lateral connections in animals and in PGLISSOM. In the tree shrew V1, biocytin was injected in the cell body of seven different neurons, and the projections going to neurons of different orientation preferences were counted. The thin line with circles shows the median percentage of connections for each difference (adapted from Bosking et al. 1997). In the GMAP, the percentage of connections to neurons with different orientations were similarly counted (after pruning); the median over all neurons in the map is shown as the thick line. Both plots peak at 0^o, and quickly fall off as the orientation differences become larger (this effect is slightly exaggerated in the model because in this experiment it was trained on straight elongated Gaussians only; cf. Section 13.4.2). In other words, strong excitatory lateral connections mostly link neurons with similar orientation tuning both in the model and in animals.