The current model of the organization of basal ganglia was proposed in the 1980s following key observations made on animal models of neurodegenerative diseases and patients who had hypo-or hyperkinetic movement disorders.I4 This model rapidly became the ultimate way of interpreting how basal ganglia worked in health and disease, and it has led to a revival of neurosurgical therapies for Parkinson's disease (PD)."' During the last few years, however, various shortcomings of this model became apparent, even to those who first proposed this scheme of
In this article, we underline some of the major problems that we and others have noted with regard to the current model of basal ganglia. We argue that this model has failed to integrate new pieces of essential information about the anatomic and functional organization of basal ganglia and has thus become obsolete.
THE MODEL
The striaturn (STR) constitutes the input stage of the basal ganglia. It receives multiple afferent projections, the major one being the glutamatergic excitatory input from the cerebral cortex. In contrast, the internal segment of the globus pallidus (GPi) and the substantia nigra pars reticulata (SNr) represent the major output nuclei of basal ganglia. These structures exert a tonic GABAergic inhibitory influence on the excitatory premotor neurons