Metathalamus

View Details

Status

Done

Parent item

Diencephalon

General

• Consists of
• Medial geniculate bodies
• Lateral geniculate bodies
• Geniculate because each mass of grey matter is bent on itself

• Shaped
• small oval collections of grey matter

• Location
• Superiorly: posterior part of the thalamus
• Medially: Colliculi of the midbrain

Medial geniculate body

• A relay station on the auditory pathway.

• Has 3 different types of nuclei
• Medial nuclei
• Ventral nuclei
• Different neurons in the ventral nucleus of the medial geniculate body respond to different frequencies of sound (tonotopic organization).
• The ventral nucleus projects to the primary auditory cortex (herschl gyrus).
• Dorsal nuclei
• The neurons in the dorsal nucleus do not show tonotopic organization.
• They project to auditory areas around the primary auditory area.

• Afferents
• Ascending
• Lateral lemniscus either directly or after relay in the inferior colliculus
• These fibres pass through the brachium of the inferior colliculus.
• Each medial geniculate body receives impulses from the cochleae of both sides.
• Descending
• Auditory area of the cerebral cortex (part of the descending auditory pathway)

• Efferent
• Auditory radiation
• arising in the medial geniculate body
• Passes through the sublentiform part of the internal capsule
• Terminate in the primary auditory area (Area 41,42) of the cerebral cortex.

Lateral Geniculate Body

• A relay station on the visual pathway.

• Location
• Superiorly: pulvinar separated from it by the brachium of superior colliculus.
• It lies anterolateral to the medial geniculate body

• Afferents
• Retinae of both eyes
• Primary visual cortex and extrastriate visual areas.
• Superior colliculus
• Reticular formation of the pons and medulla.
• Noradrenergic fibres reach it from the locus coeruleus, and
• Serotoninergic fibres from raphe nuclei (midbrain)

• Efferent
• Optic radiation
• Arise in the lateral geniculate body
• Passes through the retrolentiform part of the internal capsule to reach the primary visual area (Area 17) of the occipital lobe of the cerebral cortex.