Subthalamus – Anatomy
Most of the subthalamus is just a rostral extension of the midbrain, with parts of the substantia nigra and the red nucleus, and the midbrain reticular formation, which is called the zona incerta in the subthalamus. In addition, it contains one nucleus, conveniently called the subthalamic nucleus. The subthalamic nucleus plays a role in motor control and is interconnected with the basal ganglia.
The Subthalamus lies between the midbrain and thalamus, medial to internal capsule and the globus pallidus. It consisits of the following:
The cranial ends of the red nucleus and substantia nigra extend int it.
Cranial ends of the lemnisci, lateral to the red nucleus.
Dentatothalamic tract along with the subthalamic fibers.
Fasciculus lenticularis (dorsal).
Subthalamic fasciculus (intermediate fibers)
The subthalamus is represented mainly by the subthalamic nucleus, a lens-shaped structure lying behind and to the sides of the hypothalamus and on the dorsal surface of the internal capsule. The subthalamic region is traversed by fibers related to the globus pallidus. Discrete lesions of the subthalamic nucleus produce hemiballismus, a violent form of dyskinesia in which the limbs are involuntarily flung about.
The subthalamic nuclei are small paired structures that are part of the functional basal ganglia. They are located ventral to the thalamus, dorsal to the substantia nigra and medial to the internal capsule.
The subthalamic nucleus receives its main input from the lateral pallidum (external segment of the globus pallidus). Excitatory, glutamatergic inputs come from the cerebral cortex (particularly the motor cortex), and from the pars parafascicular of the central complex. There are also neuromodulatory inputs from the substantia nigra pars compacta.
The axons of its neurons leave the nucleus dorsally. The efferent axons are glutamatergic and most of the subthalamic principal neurons are directed to the other elements of the core of the basal ganglia.
It was first described by Jules Bernard Luys in 1865 and the term corpus Luysi or Luys’ body is still sometimes used.
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