Summary
The basal ganglia consist of a variety of subcortical nuclei engaged in motor control and executive functions, such as motor learning, behavioral control, and emotion. The striatum, a major basal ganglia component, is particularly useful for cognitive planning of purposive motor acts owing to its structural features and the neuronal circuitry established with the cerebral cortex. Recent data indicate emergent functions played by the striatum. Indeed, cortico‐striatal circuits carrying motor information are paralleled by circuits originating from associative and limbic territories, which are functionally integrated in the striatum. Functional integration between brain areas is achieved through patterns of coherent activity. Coherence belonging to cortico‐basal ganglia circuits is also present in Parkinson’s disease patients. Excessive synchronization occurring in this pathology is reduced by dopaminergic therapies. The mechanisms through which the dopaminergic effects may be addressed are the object of several ongoing investigations. Overall, the bulk of data reported in recent years has provided new vistas concerning basal ganglia role in the organization and control of movement and behavior, both in physiological and pathological conditions. In this review, basal ganglia functions involved in the organization of main movement categories and behaviors are critically discussed. Comparatively, the multiplicity of Parkinson’s disease symptomatology is also revised.
1 INTRODUCTION
The components of the basal ganglia (BG) system, including the striatum, are bilateral structures that, like the thalamus, serve behavior and movement control through the regulation of cortical output. The BG operate in close relation with the cerebral cortex being part of an extensive loop, the BG‐thalamic‐cortical system, and their association results in several processing circuits between different cortical areas.1, 2 Parallel cortical‐BG‐thalamocortical information flows through two pathways having opposite effects, the direct and indirect pathways,3 whose functioning is crucial for the proper execution of movement. Choosing the contextually appropriate response in the presence of competing alternatives is a critical aspect of motor control.4, 5 Direct and indirect pathways provide the neural mechanism to rapidly switch from a planned to an alternative response.6 The main BG input nucleus, through which the direct and indirect pathways manage cortical information, is the striatum that receives topographical excitatory projections from almost the entire cortical areas. Recent data indicate emergent functions played by the striatum. Indeed, cortico‐striatal circuits carrying motor information are paralleled by circuits originating from associative and limbic territories that are functionally integrated in the striatum. The striatal ability to switch from competing sensory‐motor processes, in response to specific context and situations, is based on its capability in processing, routing, and reverting cortical information.7, 8 Owing to its structural features and the neuronal circuitry established with the cerebral cortex, the striatum is particularly useful for cognitive planning of purposive motor acts. The peculiar striatal regional differentiation, as visible from histochemical evidence, and the circuitry features enable the BG system to operate a functional integration between brain areas.
Overall, the bulk of data reported in recent years has provided new vistas concerning BG role in the organization and control of movement and behavior, both in physiological and pathological conditions. In this review, BG functions involved in the organization of main movement categories and behaviors are critically discussed. Comparatively, the multiplicity of Parkinson’s disease (PD) symptomatology is also revised.[…]
TBI Rehabilitation 