lateral lemniscus

Information about lateral lemniscus

Brain:
Figure 1: Arrangement of the lateral lemniscus, showing the tract and nuclei. Dorsal nucleus of the lateral lemniscus (DNLL), Intermediate nucleus of the lateral lemniscus (INLL), ventral nucleus of the lateral lemniscus (VNLL).
Latinlemniscus lateralis
subject #188 805
NeuroNameshier-605
Dorlands/Elsevier l_06/12483107
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.

Connections

The brainstem nuclei include:
  • the superior olive
  • the intermediate nucleus of the lateral lemniscus (INLL)
  • the ventral nucleus of the lateral lemniscus (VNLL)
  • the dorsal nucleus of the lateral lemniscus (DNLL)
Fibers leaving these brainstem nuclei ascending to the inferior colliculus rejoin the lateral lemniscus. In that sense, this is not a 'lemniscus' in the true sense of the word (second order, decussated sensory axons), as there is third (and out of the lateral superior olive, fourth) order information coming out of some of these brainstem nuclei.

The lateral lemniscus is located where the cochlear nuclei and the pontine reticular formation (PRF) crossover. The PRF descends the reticulospinal tract where it innervates motor neurons and spinal interneurons. It is the main auditory tract in the brainstem which connects the superior olivary complex (SOC) with the inferior colliculus (IC). The Dorsal Cochlear Nucleus (DCN) has input from the LL and output to the contralateral LL via the ipsilateral and contralateral Dorsal Acoustic Stria.

There are three small nuclei on each of the lateral lemnisci; the ventral, dorsal and the intermediate. The two lemnisci communicate via the commissural fibres of Probst.

Function of this structure

This part of the brain also functions in identifying the onset of the sound, the duration of the sound and also with monaural volume.

The function of the lateral lemniscus is not known; however it has good temporal resolution compared to other cells higher than the cochlear nuclei and is sensitive to both timing and amplitude changes in sound. It is also involved in the acoustic startls reflex; the most likely region for this being the VNLL.

The cells of the DNLL respond best to bilateral inputs. Sound in the contralateral ear leads to the strongest responses in the VNLL which deals with some temporary processing. The VNLL may also be essential to the IC’s decoding of amplitude modulated sounds.

DNLL cells have onset and complexity tuned sustained responses. VNLL cells have little spontaneous activinty, broad and moderately complex tuning curves; they have both phasic and tonic responses and are involved in temporal processing.

INLL also has little spontaneous activity and broad tuning curves. The temporal responses are significantly different to cells of the VNLL.

Inputs and outputs to nuclei

The table below shows that each of the nuclei have a complicated arrangement of ipsilateral and contralateral afferent inputs and outputs.

NucleusInputOutput
 ContralateralIpsilateralContralateralIpsilateral
VNLL Anterior and posterior ventral cochlear nucleiMedial nucleus of the trapezoid body Inferior Colliculus

DNLL

INLLAnterior and posterior Ventral Cochlear NucleusMedial nucleus of the trapezoid body Medial Geniculate body

Inferior Colliculus

DNLLAnterior Ventral

Cochlear nucleus (and Bilateral)

Medial superior Olivary Nucleus

Lateral Superior Olivary Nucleus (and Bilateral)

DNLL

Inferior Colliculus

Mid brain reticular formation

Superior Olivary Complex

Inferior Colliculus

 Medial Geniculate Body

Mid brain reticular formation

Superior Olivary Complex

Additional images


Dissection of brain-stem. Lateral view.

Deep dissection of brain-stem. Lateral view.

Deep dissection of brain-stem. Lateral view.

Deep dissection of brain-stem. Ventral view.

Dissection of brain-stem. Dorsal view.

Coronal section through mid-brain.

Transverse section of mid-brain at level of inferior colliculi.

Scheme showing the course of the fibers of the lemniscus; medial lemniscus in blue, lateral in red.




 •  • [ e]
Sensory system: Auditory and Vestibular systems
Outer earPinna (Helix, Antihelix, Tragus, Antitragus, Earlobe) • Ear canal
Middle earEardrum • Ossicles (Malleus, Incus & Stapes) • Stapedius • Tensor tympani • Eustachian tube (Torus tubarius)
Inner ear/LabyrinthBony labyrinth (Vestibule) • Membranous labyrinth
Oval window • Helicotrema • Round window
Cochlea: Spiral ganglion • Modiolus • Cochlear duct/scala media (Endolymph, Stria vascularis, Spiral ligament, Organ of Corti) • Scala vestibuli and Scala tympani (Perilymph)
Reissner's/vestibular membrane • Basilar membrane • Tectorial membrane
Organ of Corti: Hair cells • Stereocilia • Sulcus spiralis (externus, internus) • Limbus spiralis
Vestibular systemStatic/translations: Utricle (Macula) - Saccule (Macula, Endolymphatic sac, Endolymphatic duct) - Kinocilium - Otolith
Kinetic/rotations: Semicircular canals (Superior, Posterior, Horizontal) • Cupula • Ampullae (Crista ampullaris)
Brain (auditory)Cochlear nerve VIII → Cochlear nuclei → Superior olivary nuclei → Lateral lemniscus → Inferior colliculi → Medial geniculate nuclei → Primary auditory cortex


 •  • [ e]
Brain: mesencephalon (midbrain)
TectumCorpora quadrigemina (Inferior colliculi, Superior colliculi) • Subcommissural organ • Pretectum
Peduncle tegmentumPeriaqueductal gray (Cerebral aqueduct, Dorsal raphe nucleus) • Ventral tegmentum • Pedunculopontine nucleus • Red nucleus • MLF (riMLF)  • lemnisci (Medial, Lateral) • cranial nuclei (III: Oculomotor nucleus, III: Edinger-Westphal nucleus, IV: Trochlear nucleus, V: Mesencephalic)
Peduncle baseSubstantia nigra • Cerebral crus (Corticospinal tract, Corticobulbar tract, Corticopontine tract/Frontopontine fibers/Temporopontine fibers)
Latin}}} 
Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
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NeuroNames is a system of nomenclature for the human and/or macaque brain.

It is maintained by the University of Washington and is a part of a tool called "BrainInfo". BrainInfo helps one identify structures in the brain.
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Elsevier, the world's largest publisher of medical and scientific literature, forms part of the Reed Elsevier group. Based in Amsterdam, the company has substantial operations in the UK, USA and elsewhere.
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axon or nerve fiber, is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma.

Anatomy


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The brain stem is the lower part of the brain, adjoining and structurally continuous with the spinal cord. Most sources consider the pons, medulla oblongata, and midbrain all to be part of the brainstem.
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The cochlear nuclei consist of:
  • (a) the dorsal cochlear nucleus, corresponding to the tuberculum acusticum on the dorso-lateral surface of the inferior peduncle; and
  • (b) the ventral or accessory cochlear nucleus

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The inferior colliculi (Latin, lower hill) together with the superior colliculi form the eminences of the corpora quadrigemina, and also part of the tectal region of the midbrain.
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superior olivary nucleus (or superior olivary complex or superior olive) is a small mass of gray substance situated on the dorsal surface of the lateral part of the trapezoid body.
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A lemniscus (Greek for ribbon[1]) can refer to:
  • In mathematics, a lemniscate
  • In anatomy, a part of the brain, such as the medial lemniscus or lateral lemniscus

References

1.

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superior olivary nucleus (or superior olivary complex or superior olive) is a small mass of gray substance situated on the dorsal surface of the lateral part of the trapezoid body.
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The cochlear nuclei consist of:
  • (a) the dorsal cochlear nucleus, corresponding to the tuberculum acusticum on the dorso-lateral surface of the inferior peduncle; and
  • (b) the ventral or accessory cochlear nucleus

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The reticular formation is a part of the brain which is involved in stereotypical actions, such as walking, sleeping, and lying down. It is essential for governing some of the basic functions of higher organisms, and phylogenetically one of the oldest portions of the brain.
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superior olivary nucleus (or superior olivary complex or superior olive) is a small mass of gray substance situated on the dorsal surface of the lateral part of the trapezoid body.
..... Click the link for more information.
The inferior colliculi (Latin, lower hill) together with the superior colliculi form the eminences of the corpora quadrigemina, and also part of the tectal region of the midbrain.
..... Click the link for more information.
The dorsal cochlear nucleus (DCN, also known as the "tuberculum acousticum"), is a cortex-like structure on the dorso-lateral surface of the brainstem. Along with the ventral cochlear nucleus, it forms the cochlear nucleus, where all auditory nerve fibers from the cochlea form
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sensory system: in this case, vision, for the visual system. ]]

A sensory system is a part of the nervous system responsible for processing sensory information.
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The auditory system is the sensory system for the sense of hearing.

Ear

Main article: Ear

Outer ear

Main article: Outer ear

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The vestibular system, or balance system, is the sensory system that provides the dominant input about our movement and orientation in space. Together with the cochlea, the auditory organ, it is situated in the vestibulum in the inner ear (Figure 1).
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The outer ear is the external portion of the ear.

Pinna, or auricle

The visible part is called the pinna and functions to collect and focus sound waves. Many mammals can move the pinna (with the auriculares muscles) in order to focus their hearing in a certain direction
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The pinna (Latin for feather) is the visible part of the ear that resides outside of the head (this may also be referred to as the auricle or auricula).

Purpose

The purpose of the pinna is to collect sound.
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The prominent rim of the auricula is called the helix. Where the helix turns downward behind, a small tubercle is frequently seen: the auricular tubercle of Darwin.

Additional images



The muscles of the auricula.

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antihelix, also known as the anthelix; this divides above into two crura, between which is a triangular depression, the fossa triangularis.

Additional images



The muscles of the auricula.

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tragus, so called from its being generally covered on its under surface with a tuft of hair, resembling a goat’s beard, "goat" being the origin of the word, from the Greek tragos.
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antitragus.

External links

  • SUNY Labs 30:01-0105
  • Norman/Georgetown lesson3 ( externalear ) (#6)
  • Diagram at bodymodforums.

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On the ear of humans and many other animals, the earlobe (lobulus auriculæ, sometimes simply lobe or lobule) is the soft lower part of the Cory Drosen's ear, similar in composition to the labia, or pinna.
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The ear canal (external auditory meatus, external acoustic meatus), is a tube running from the outer ear to the middle ear. The ear canal extends from the pinna to the eardrum and is about 26 mm in length and 7 mm in diameter.
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The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. The mammalian middle ear contains three ossicles, which couple vibration of the eardrum into waves in the fluid and membranes of the inner ear.
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The tympanic membrane, colloquially known as the eardrum, is a thin membrane that separates the external ear from the middle ear. Its function is to transmit sound vibrations from the air, conducted through the external acoustic meatus to the ossicles inside the
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The ossicles (also called auditory ossicles) are the three smallest bones in the human body. They are contained within the middle ear space and serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea).
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malleus or hammer is a hammer-shaped small bone or ossicle of the middle ear which connects with the incus and is attached to the inner surface of the eardrum. The word is Latin for hammer.
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