Subthalamus

The subthalamus or ventral thalamus is a part of the diencephalon. Its most prominent structure is the subthalamic nucleus. The subthalamus connects to the globus pallidus, a subcortical nucleus of the basal ganglia.

Structure

The subthalamus is located ventral to the thalamus, medial to the internal capsule and lateral to the hypothalamus. It is a region formed by several grey matter nuclei and their associated white matter structures, namely:

The subthalamic nucleus, whose neurons contain glutamate and have excitatory effects over neurons of globus pallidus and substantia nigra
Zona incerta, located between fields of Forel H₁ and H₂. It is continuous with the thalamic [reticular nucleus] and receives input from the primary [motor cortex|precentral cortex].
Subthalamic fasciculus, formed by fibers that connect the globus pallidus with the subthalamic nucleus
Fields of Forel
Ansa lenticularis

During development the subthalamus is continuous with the hypothalamus, but is separated by white matter fibres mainly from the internal capsule. Caudally, the subthalamus or prethalamus is separated from the thalamus by the zona limitans intrathalamica.
Postnatally, the subthalamus lies beneath the thalamus, hence 'sub' 'thalamus'. It also lies dorsolateral to the hypothalamus.

The subthalamus develops efferent connections to the striatum in the telencephalon, to the dorsal thalamus in the diencephalon, and to the red nucleus and substantia nigra in the mesencephalon. It receives afferent connections from the substantia nigra and striatum.