Figure 7.

The responses of the Exc group neurons (identified by their neuron id on the y-axis) were tested for all 40 grating orientations. One orientation was presented per second and the test ran for 40 s (x-axis). (A) Neuronal spike responses of 400 neurons trained with the highest fitness SNN parameters found using the parameter tuning framework. (B) Neuronal spike responses of 400 neurons trained using a single set of low fitness parameters. The neurons were arranged such that those neurons responding to similar orientations were grouped together for both (A,B). This accounts for the strong diagonal pattern found in (A) and the very faint diagonal pattern found in (B). Neuronal spike responses in (A) are sparse in that relatively few neurons code for one orientation while neuronal spike responses in (B) are not sparse. Additional, many of the neuronal spike responses in part (A) employ a wide range of firing rates to describe a subset of the orientation stimulus space while spike responses in (B) have similar firing responses across all angles in all cases.