Brain and nerve = Shinkei kenkyū no shinpo
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Review
[Cortico-basal ganglia circuits--parallel closed loops and convergent/divergent connections].
The basal ganglia play important roles not only in motor control but also in higher cognitive functions such as reinforcement learning and procedural memory. Anatomical studies on the neuronal connections between the basal ganglia, cerebral cortex, and thalamus have demonstrated that these nuclei and cortical areas are interconnected via independent parallel loop circuits. The association, motor, and limbic cortices project to specific domains in the striatum, which, in turn, project back to the corresponding cortical areas via the substantia nigra/globus pallidus and the thalamus. ⋯ It has also been suggested that the location of the substantia nigra is in such that it can transmit information from the 'limbic loop' to the 'association loop', and from the 'association loop' to the 'motor loop'. Furthermore, a recent transsynaptic neuronal tracing study conducted at our laboratory demonstrated that the ventral (limbic) striatum sends divergent outputs to multiple regions in the frontal cortex. These 'inter-loop' connections would be important for the integration of information to achieve goal-directed behaviors.
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Deep brain stimulation (DBS) has proved highly effective in the treatment for Parkinson's disease and dystonia. Presently, many types of dopamine agonists, monoamine oxidase B (MAOB) inhibitors, catechol-O-methyltransferase (COMT) inhibitor or other antiparkinsonian drugs are being developed. However, it is still very difficult to medically treat motor complications associated with levodopa therapy. ⋯ The brain mechanism underlying the improvement of pallidal DBS in dystonia has been unclear. Many studies on DBS in Parkinson's disease and dystonia have been carried out to elucidate the clinical outcomes and/or the underlying neurophysiological mechanisms. In this review, the clinical outcomes of DBS for Parkinson's disease and dystonia will be focused on.