The Basal Ganglia
The basal ganglia (BG) are known to play a role in motor, cognitive and associative functions (see Sect. 1 of Part I of The Subthalamic Nucleus). However, the role of the BG in motor control appears to be the dominant one, and will be the emphasis of this research. It is widely accepted that the BG play a crucial role in the control of voluntary movement. However, what exactly the BG do for voluntary movement is still under debate. Many clues as to the function of this complex group of subcortical structures have been obtained by examining the deficits that occur following disorders of the BG such as PD and Huntington’s disease. Animal models of MPTP-induced parkinsonism have played a crucial role in investigations. Single-cell microelectrode recordings of neuronal activity, as well as imaging studies of blood flow and metabolism have also been employed in an effort to understand the complex interactions between BG nuclei during the execution of movement in normal and parkinsonian subjects. However, despite extensive research on the subject, the function of the BG within the cortico-BG-thalamocortical circuit is still unclear.
The roles attributed to the BG fall into two general categories: those that are directly related to the production of movement, namely focussed selection and inhibition of competing programmes, movement gating and velocity regulation, and action selection; and those that are based on the strengthening of corticostriatal synapses, which may play a role in the learning of movement sequences, namely sequence generation and reinforcement learning.
KeywordsBasal Ganglion Deep Brain Stimulation Subthalamic Nucleus Indirect Pathway Direct Pathway
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