GABAergic excitation in striatal projection neurons: Simulations and experiments

It has been suggested that one of the main functions of the striatum is to detect and classify cortical representations of sensory events to trigger appropriate motor responses through a “winner-takes-all” network dynamic mediated by GABAergic interactions between striatal projection neurons. However, it is possible that, under some conditions GABAergic inputs may exert an excitatory rather than inhibitory effect. To determine whether GABAergic inputs to striatal neurons are inhibitory or excitatory, we performed a combination of simulations and experiments. We found that GABAergic post-synaptic potentials can exert excitatory effects on projection neurons, and this ability crucially depends on the timing between the GABAergic event and a concomitant depolarizing input. This finding has potentially radical implications for computational theories of striatal function, and suggests that, under appropriate conditions, striatal neurons may cooperate to perform computations of complexity extending beyond a “winner-takes-all” classification of cortical inputs.