Excitatory and Inhibitory Subnetworks Are Equally Selective during Decision-Making and Emerge Simultaneously during Learning

Inhibitory neurons play a critical role in decision-making models and are often simplified as a single pool of non-selective neurons lacking connection specificity. This assumption is in keeping with observations in primary visual cortex: inhibitory neurons are broadly tuned in vivo, and show non-specific connectivity in slice. Selectivity of excitatory and inhibitory neurons within decision circuits is not known. We simultaneously measured their activity in the posterior parietal cortex of mice making multisensory decisions. Surprisingly, excitatory and inhibitory neurons were equally selective for the animal’s choice, both at the single cell and population level. Further, excitatory and inhibitory populations exhibited similar changes in selectivity and temporal dynamics during the transition from novice to expert decision-making, paralleling behavioral improvements. These observations, combined with simulations, argue against models assuming non-selective inhibitory neurons. Instead, they argue for selective subnetworks of inhibitory and excitatory neurons that are shaped by experience to support expert decisionmaking.