The neostriatum viewed orthogonally.

The work described in this paper suggests that: (1) the neostriatum (a tier of the forebrain) is functionally heterogeneous, i.e. different neostriatal regions mediate responses in different situations; (2) regional specialization may be attributed to selective cortico-neostriatal connections, as indicated by anatomical and neurobehavioural evidence and studies with 2-deoxyglucose; (3) cortical areas and their corresponding principal neostriatal regions are organized 'in series'; (4) small lesions which cause severe but specific 'cognitive' effects do not induce movement disorders; (5) the transmitter of the cortico-neostriatal connections is glutamate. This work and other evidence suggests that the forebrain consists of systems that each contain a 'specific' thalamic nucleus and its associated cortical area and neostriatal region. This view, with three additional assumptions, can tentatively explain not only experimental neurobehavioural results but also certain symptoms of diseases involving the neostriatum.