Abstract
Categorical neural representations underlie various forms of selection and decision-making. They promote robust signaling of the winner in the presence of input ambiguity and neural noise. Here, we show that a ‘donut-like’ inhibitory mechanism in which each competing option suppresses all options except itself is highly effective at generating categorical responses. It surpasses motifs of feedback inhibition, recurrent excitation, and divisive normalization used in decision-making models. We demonstrate experimentally not only that this mechanism operates in the midbrain spatial selection network in barn owls, but also that it is required for categorical signaling by it. Moreover, the pattern of inhibition forms an exquisitely structured ‘multi-holed’ donut consistent with this network’s combinatorial inhibitory function. Self-sparing inhibition may be a powerful circuit module central to categorical selection.








