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The basal ganglia (or basal nuclei) are a group of nuclei in the brain interconnected with the cerebral cortex, thalamus and brainstem. Mammalian basal ganglia are associated with a variety of functions: motor control, cognition, emotions, and learning. In modern use the term ‘ganglia’ is in this instance considered a misnomer; ‘ganglion’ refers to concentrations of neural nuclei in the periphery only (for example those of the autonomic nervous system), and the term ‘basal nuclei’ is preferred.
The acceptance that the basal ganglia system constitutes one major cerebral system has been slow to appear.
The first anatomical identification of distinct subcortical structures was published by Thomas Willis in 1664.[1] For many years, the term corpus striatum was used to describe a large group of subcortical elements, some of which were later discovered to be functionally unrelated. Additionally, the putamen and the caudate nucleus were not linked together. The putamen was thought to be associated to the pallidum in what used to be called the “nucleus lenticularis” (see lentiform nucleus on the fig.).
Pioneering work by Cécile and Oskar Vogt (1941) greatly simplified the description of the basal ganglia by proposing the term striatum to describe the group of structures consisting of the caudate nucleus, the putamen and the mass linking them ventrally, the nucleus accumbens.
The striatum gets its name from the striated appearance created by radiating dense bundles of striato-pallido-nigral axons, described by anatomist Kinnear Wilson as “pencil-like”. The anatomical link of the striatum with its primary targets, the pallidum and the substantia nigra was later discovered. Together, these structures constitute the striato-pallido-nigral bundle, which is the core of the basal ganglia. This nerve bundle forms the so-called “comb bundle of Edinger” when it crosses the internal capsule.
Additional structures that later became associated with the basal ganglia are the “body of Luys” (1865) (nucleus of Luys on the figure) or subthalamic nucleus, whose lesion was known to produce movement disorders. More recently, other areas such as the central complex (centre médian-parafascicular) and the pedunculopontine complex have been thought to be regulators of the basal ganglia.
At the beginning of the 20th century, the basal ganglia system was associated with motor functions, as lesions of these areas would often result in disordered movement in humans (chorea, athetosis, Parkinson’s disease).
The five individual nuclei that make up the primate basal ganglia, along with their major subdivisions, are:
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