Thalamic interaction between the input and the output systems of the basalganglia

The striatal return through the thalamus is largely neglected in current st udies dealing with basal ganglia function, and its role within this circuit ry remains obscure. In this contribution the thalamus is regarded as an imp ortant place of interaction between the input and the output organization o f the basal ganglia. In support of this idea, a brief overview is provided of some of the most recent findings concerning the thalamus in relation to the basal ganglia circuitry. In particular, we have focused on the thalamos triatal projections themselves, on the output of the basal ganglia to the t halamus and also on the overlapping territories between the thalamic projec tion of the output nuclei and the thalamostriatal neurons. These data suppo rt the existence of several thalamic feedback circuits within the basal gan glia neural system. Finally, some considerations are provided upon the func tional significance of these thalamic feedback circuits in the overall orga nization of the basal ganglia. (C) 1999 Elsevier Science B.V. All rights re served.