| Brain: Inferior colliculus | ||
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| Transverse section of mid-brain at level of inferior colliculi. | ||
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| Deep dissection of brain-stem. Lateral view. ("Inferior colliculus" is yellow, and is labeled at left. | ||
| Latin | colliculus inferior | |
| Gray's | subject #188 806 | |
| Part of | Tectum | |
| System | Auditory system | |
| NeuroNames | hier-467 | |
| MeSH | Inferior+Colliculus | |
The inferior colliculi (Latin, lower hills) together with the superior colliculi form the eminences of the corpora quadrigemina, and also part of the tectal region of the midbrain. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. This is a list of the subjects in Gray's Anatomy: IX Neurology The tectum (Latin roof) is a region of the Brain, specifically the dorsal part of the Mesencephalon (midbrain The auditory system is the Sensory system for the sense of hearing. NeuroNames is a system of nomenclature for the human and/or macaque Brain. Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. The superior colliculus ( Latin, higher hill) is a paired structure that is part of the Brain 's tectal area. In the Brain, the corpora quadrigemina ( Latin for "quadruplet bodies" are the four colliculi—two inferior, two superior —located The tectum (Latin roof) is a region of the Brain, specifically the dorsal part of the Mesencephalon (midbrain In biological anatomy the mesencephalon (or midbrain) comprises the Tectum (or corpora quadrigemini Tegmentum, the ventricular mesocoelia (or "iter" The inferior colliculus lies caudal to its counterpart - the superior colliculus - above the trochlear nerve, and at the base of the projection of the medial geniculate nucleus (MGN) and the lateral geniculate nucleus (LGN). The trochlear nerve (the fourth cranial nerve, also called the fourth nerve or simply IV) is a motor nerve (a “somatic efferent” nerve that innervates The Medial Geniculate Nucleus or Medial Geniculate Body (MGB is part of the auditory Thalamus and represents the thalamic relay between the Inferior colliculus The lateral geniculate nucleus ( LGN) of the Thalamus is a part of the Brain, which is the primary processor of visual information received from the
The inferior colliculus is the principal midbrain nucleus of the auditory pathway and receives input from several more peripheral brainstem nuclei in the auditory pathway, as well as inputs from the auditory cortex. The inferior colliculus has many subnuclei.
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Relationship to auditory system
The inferior colliculi of the midbrain, are located just below the visual processing centers known as the superior colliculi. The inferior colliculus is the first place where vertically orienting data from the fusiform cells in the dorsal cochlear nucleus can finally synapse with horizontally orienting data. The cochlear nuclei consist of (a the Dorsal cochlear nucleus, corresponding to the Tuberculum acusticum on the dorso-lateral surface of This homecoming of the aural dimensions puts these dual mesencephalic bumps in the position to fully integrate all the sound location data.
The inferior colliculus function as a master computer both in regard to its hardware (complex connections) and its software (internal organization). IC are large auditory nuclei on the right and left sides of the midbrain. It is divided into three parts, the Central Nucleus of IC (CNIC), pericentral nucleus and external nucleus; however, CNIC is the principal way station for ascending auditory information in the IC.
1. Input and Output Connection of IC
The input connections to the inferior colliculus are composed of many brainstem nuclei. All nuclei except the contralateral ventral nucleus of the lateral lemniscus (LL) send projections to the central nucleus (CNIC) bilaterally. 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 It has been shown that great majority of auditory fibers ascending in the lateral lemniscus terminate in the CNIC. In addition, the IC receives descending inputs from the auditory cortex, medial geniculate body (MGB), and superior colliculus (SC).
The inferior colliculus receives input from both the ipsilateral and contralateral cochlear nucleus and respectively the corresponding ears. Of course, there is some lateralization, the dorsal projections (containing vertical data) only project to the contralateral inferior colliculus. A Longitudinal fissure separates the Human brain into two distinct Cerebral hemispheres connected by the Corpus callosum. This inferior colliculus contralateral to the ear it is receiving the most information from, then projects to its ipsilateral medial geniculate nucleus.
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Location |
Input |
Output |
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IC |
CNIC |
Contralateral -AVCN -PVCN -SCN |
Ipsilateral -LSO -MSO -DNLL |
-MGB -Auditory Cortex -Deep layers of the SC -Contralateral and other nuclei in the ipsilateral IC -Reticular Formation -Periaqueductal Gray -TB |
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Peicentral nucleus |
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External nucleus |
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The medial geniculate body (MGB) is the output connection from interior colliculus and the last subcortical way station. The MGB is composed of ventral, dorsal, and medial divisions, which are relatively similar in humans and other mammals. The ventral division receives auditory signals from the central nucleus of the IC (1).
Abbreviation
CNIC: Central Nucleus of IC
AVCN: Anterior Ventral Cochlear Nucleus
PVCN: Posterior Ventral Cochlear Nucleus
SCN: Superior Colliculus Nucleus
LSO: Lateral Superior Olive
MSO: Medial Superior Olive
DNLL: Dorsal Nucleus of the Lateral Lemniscus
MGB: Medial Geniculate Body
SC: Superior Colliculus
TB: Trapezoid Body
2. Function of IC
The majority of the ascending fibers from LL project to IC, which means major ascending auditory pathway coverage in here. IC appears as an integrative station and switchboard as well. It is involved integration and routing of multi-model sensory perception, mainly startle reflex and ocular reflex. It is also responsive to specific amplitude modulation frequencies and this might be responsible for detection of pitch. In addition, spatial localization by binaural hearing is a related function of IC as well.
The inferior colliculus has a relatively high metabolism in the brain. The Conrad Simon memorial institute research measured the blood flow of the IC and put a number at 1. 80 cc/g/min in the cat brain. For reference, the runner up in the included measurements was the somatosensory cortex at 1. 53. This indicates that the inferior colliculus is metabolically more active than many other parts of the brain. The hippocampus, normally considered to use up a disproportionate amount of energy, was not measured or compared (6).
Skottun et al. measured the interaural time difference sensitivity of single neurons in the inferior colliculus, and used these to predict behavioural performance. The interaural time difference (or ITD when concerning humans or animals is the difference in arrival time of a sound between two ears The predicted just noticable difference was comparable to that achieved by humans in behavioral tests (7). In Psychophysics, a just noticeable difference, customarily abbreviated with lowercase letters as jnd, is the smallest difference in a specified modality of sensory This suggested that by the level of the inferior colliculus, integration of information over multiple neurons is unnecessary (see population code). Population encoding is a means by which information about something is encoded in a group of neurons
See also
References
1) Stanley A. The auditory system is the Sensory system for the sense of hearing. Anatomical regions of the brain are listed vertically following hierarchies that are standard in Neuroanatomy. Gelfand "Hearing, an Introduction to Psychological and Physiological Acoustics", 4th Ed. , Marcel Dekker, 2004 pp 71-75
2) Conrad Simon Memorial Research Initiative homepage <http://www.conradsimon.org/InferiorColliculus.shtml>
3) Skottun, Bernt C. et al. The ability of inferior colliculus neurons to signal differences in interaural delay. PNAS November 20, 2001 vol. 98 . no. 24 . pp 14050-14054
Additional images
 Superficial dissection of brain-stem. Lateral view. |
 Deep dissection of brain-stem. Lateral view. |
 Dissection of brain-stem. Dorsal view. |
 Hind- and mid-brains; postero-lateral view. |
External links
Dictionary
inferior colliculus
-noun
- The nucleus just caudal to the superior colliculus, which is involved in the relay of auditory information
- Projects to the medial geniculate nucleus
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