Anatomy
This nucleus is located medially to the internal capsule, ventral to the thalamus, and is contiguous with the thalamic reticular nucleus. The nucleus separates the lenticular fasciculus from the thalamic fasciculus (also known as the "field H1 of Forel") . Its cells are very heterogeneous differing widely in their shape and size. Its chemoarchitecture is also diverse containing up to 20 different types of neurochemically defined cells. It has been noted that "There are few diencephalic regions that have as much cellular and neurochemical diversity".
In rats four areas are usually identified.
- a rostral sector that has densely packed spindle-shaped cells and scattered larger oval shaped cells.
- a dorsal sector that has medium-sized oval-shaped cells.
- a ventral sector made up of medium-sized multipolar or fusiform shaped cells that are more densely packed than the cells in the dorsal sector
- a caudal sector made up of small and medium-sized somata that are either multipolar, fusiform or rounded in shape, together with a group of very large multipolar-shaped cells located medially. This is sometimes called the motor part of the zona incerta nucleus. This is the area targeted by deep brain stimulation area when the zona incerta is targeted in the treatment of Parkinson Disease.
These areas lack clear cell-free borders and merge into each other.
Zona incerta neurons have dendrites with a wide span 0.8 mm and their axons give off collaterals that arborized locally within the zona incerta providing a means for lateral inhibition. The ventral area of the zona incerta has been described as having "a network of GABAergic cells with widespread interconnections, so that cells in one subsector may influence the activity of cells in a different subsector".
The zona incerta together with the hypothalamus is one of the two areas of the brain that produces the neuropeptide melanin concentrating hormone. Dopaminergic ones are also more prevalent. There are in addition populations of cells producing somatostatin, angiotensin II and melanocyte stimulating hormone.
Read more about this topic: Zona Incerta
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