The brain should be best able to associate distinct behavioral responses to sensory stimuli if these stimuli evoke population firing patterns that are close to orthogonal. To investigate whether task training orthogonalizes population codes in primary visual cortex (V1), we measured the orientation tuning of 4,000-neuron populations in mouse V1 before and after training on a visuomotor task. The effect of task training on population codes could be captured by a simple mathematical transformation of firing rates, which suppressed responses to motor-associated stimuli, but only in cells responding to them at intermediate levels. This transformation orthogonalized the representations of the task orientations by sparsening the population responses to these stimuli. The strength of response transformation varied from trial to trial, suggesting a dynamic circuit mechanism rather than static synaptic plasticity. These results indicate a simple process by which visuomotor associations orthogonalize population codes as early as in primary visual cortex.

Visuomotor association orthogonalizes visual cortical population codes