Lemniscus (anatomy)

Lemniscus is a term used in anatomy to describe a bundle of secondary sensory fibers in the brainstem. The term "lemniscus" is derived from the Latin word for "ribbon," reflecting the ribbon-like shape of these fiber bundles. There are three main lemnisci in the human brain: the medial lemniscus, the lateral lemniscus, and the trigeminal lemniscus.

Medial Lemniscus

The medial lemniscus is a large ascending bundle of heavily myelinated axons that decussate, or cross, in the brainstem, specifically in the medulla oblongata. These axons carry information from the body to the thalamus about proprioception, vibration, and discriminative touch.

File:Medial lemniscus.png

Medial lemniscus pathway

Lateral Lemniscus

The lateral lemniscus is a tract of axons in the brainstem that carries information about sound from the cochlear nucleus to various brainstem nuclei and ultimately the contralateral inferior colliculus of the midbrain.

File:Lateral lemniscus.png

Lateral lemniscus pathway

Trigeminal Lemniscus

The trigeminal lemniscus is a pathway in the brainstem that carries information about discriminative sensation and conscious proprioception from the face, as well as information about deep/crude touch, pain, and temperature.

File:Trigeminal lemniscus.png

Trigeminal lemniscus pathway

Function

The lemnisci play a crucial role in the sensory system, transmitting information from the body and face to the thalamus, which then relays this information to the cerebral cortex. This allows for the perception and processing of various types of sensory information, including touch, temperature, pain, and the position of the body in space.

Clinical Significance

Damage to the lemnisci can result in a variety of sensory deficits, depending on the specific lemniscus that is affected. For example, damage to the medial lemniscus can result in loss of discriminative touch and proprioception, while damage to the lateral lemniscus can result in hearing loss.

See Also

• Brainstem
• Thalamus
• Sensory system