The Interaction of Recurrent Axon Collateral Networks in the Basal Ganglia

We have proposed that the basal ganglia act as the central switching mechanism for the action selection system of the vertebrate brain. Simulation of our functional model of basal ganglia demonstrated that their output was consistent with this action selection hypothesis. Here we extend this model by incorporating anatomically-inspired local inhibitory axon collateral networks into two basal ganglia nuclei (globus pallidus and substantia nigra pars reticulata). Through simulation it is demonstrated that the basal ganglia's ability to function as a selection mechanism is impaired by the individual addition of the collateral networks but slightly improved when they co-exist. Therefore, we predict the existence of local axon collaterals in the entopeduncular nucleus because of its functional equivalence with the substantia nigra pars reticulata. We conclude that the action selection hypothesis is supported by the continued functioning of the basal ganglia model as a switching mechanism following appropriate anatomically-inspired additions.