Brain stimulation for basal ganglia disorders

The basal ganglia (BG) have long been considered a purely motor region of the brain. However, over the last couple of decades it has progressively become clear that BG are central components of different cortical-subcortical circuits, described on a basic level as ‘motor’, ‘oculomotor’, ‘associative’ and ‘limbic’, according to the function of the cortical regions involved. In turn, each circuit encompasses multiple, functionally and anatomically distinct subcircuits. Dysfunction within these segregated circuits has been shown to cause BG disorders. Specifically, Parkinson disease (PD) and dystonia, are thought to arise from disturbances within the BGthalamo- cortical motor circuitry, whilst Tourette syndrome (TS) and obsessive-compulsive disorder (OCD), seem to be related to abnormalities within the limbic circuitry. There is also a degree of overlap between the motor and behavioural sides of BG disorders, as conditions like PD and TS are characterised by both movement disorders and neuropsychiatric symptoms.