Basalgangliad

Basalgangliad refers to the basal ganglia, a set of interconnected subcortical nuclei in the brain that regulate movement and other functions. The core components are the striatum, composed of the caudate nucleus and putamen; the globus pallidus, with its externus and internus segments; the subthalamic nucleus; and the substantia nigra, which includes the pars compacta and pars reticulata. The striatum receives extensive input from cortex, while the pallidal outputs project to thalamic nuclei that in turn connect with the cortex, forming closed cortico-basal ganglia-thalamo-cortical circuits.

Functions of the basal ganglia include initiation and control of voluntary movement, motor planning, procedural learning, and habit formation. They also contribute to aspects of eye movements, cognition, and emotion through distinct loops that link motor, associative, and limbic cortical areas with thalamic targets. The system modulates the amplitude, velocity, and selection of actions rather than producing movement directly.

Neurochemistry in the basal ganglia is characterized by dopamine, produced mainly by neurons in the substantia nigra pars compacta, which modulates activity in the striatum. GABAergic inhibition and glutamatergic excitation are prominent, with acetylcholine playing a modulatory role within the striatum.

Clinical relevance centers on movement disorders and related conditions. Parkinson’s disease involves loss of dopaminergic neurons, leading to bradykinesia, rigidity, and tremor. Huntington’s disease features degeneration of striatal neurons, producing chorea and cognitive decline. Treatment options include medications that restore dopaminergic balance and procedures such as deep brain stimulation targeting the subthalamic nucleus or the internal globus pallidus, as well as lesioning in selected cases.