Olfactory tract

Last updated
Olfactory peduncle
Cerebral Gyri - Inferior Surface2.png
Olfactory peduncle lying in olfactory sulcus and olfactory striae labelled
Details
System Olfactory system
Location Brain
Identifiers
Latin tractus olfactorius
NeuroNames 283
NeuroLex ID birnlex_1663
TA98 A14.1.09.431
TA2 5539
FMA 77626
Anatomical terms of neuroanatomy

The olfactory peduncle (olfactory tract, olfactory stalk) is a bilateral bundle of afferent nerve fibers from the mitral and tufted cells of the olfactory bulb that connects to several target regions in the brain, including the piriform cortex, amygdala, and entorhinal cortex. It is a narrow white band, triangular on coronal section, the apex being directed upward.

Contents

The term olfactory tract is a misnomer, as the olfactory peduncle is actually made up of the juxtaposition of two tracts, the medial olfactory tract (giving the medial and intermediate olfactory stria) and the lateral olfactory tract (giving the lateral and intermediate olfactory stria) [1] . However, the existence of the medial olfactory tract (and consequently the medial stria) is controversial in primates (including humans) [2] .

Structure

The olfactory peduncle and olfactory bulb lie in the olfactory sulcus [3] a sulcus formed by the medial orbital gyrus on the inferior surface of each frontal lobe. The olfactory peduncles lie in the sulci which run closely parallel to the midline. Fibers of the olfactory peduncle appear to end in the antero-lateral part of the olfactory tubercle, the dorsal and external parts of the anterior olfactory nucleus, the frontal and temporal parts of the prepyriform area, the cortico-medial group of amygdala nuclei and the nucleus of the stria terminalis. [4]

The olfactory peduncle divides posteriorly into three main branches: the medial, intermediate and lateral striae. The olfactory peduncle thus terminates in a triangular structure called the olfactory trigone. Caudal to these elements is the anterior perforated substance, the anterior part of which is marked by the relief of the olfactory tubercle. Finally, projections from the olfactory peduncle to the anterior olfactory nucleus are sometimes grouped together under the name of superior olfactory stria [1] .

The terms olfactory tubercle and olfactory trigone are commonly confused in the literature.

Medial olfactory stria

The medial olfactory stria is classically described as running medially behind the parolfactory area (hence its name) and terminating in the subcallosal gyrus.

However, this description has been rejected for some fifty years [2] . The medial olfactory stria is now described as terminating much more medially, in the ventral taenia tecta [1] .

Intermediate olfactory stria

The intermediate olfactory stria is the branch (or branches) extending from the medial or lateral olfactory striae to the olfactory tubercle and anterior perforated substance. Trolard's term "pectineal formation " is used to refer to multiple intermediate striae extending from the lateral olfactory stria [1] .

Lateral olfactory stria

The lateral olfactory stria is directed across the lateral part of the anterior perforated substance and then bends abruptly medially toward the uncus of the parahippocampal gyrus.

Clinical significance

Destruction to the olfactory peduncle results in ipsilateral anosmia (loss of the ability to smell). Anosmia either total or partial is a symptom of Kallmann syndrome a genetic disorder that results in disruption of the development of the olfactory peduncle. [5] [6] The depth of the olfactory sulcus is an indicator of such congenital anosmia. [7]

Additional images

Related Research Articles

Articles related to anatomy include:

<span class="mw-page-title-main">Frontal lobe</span> Part of the brain

The frontal lobe is the largest of the four major lobes of the brain in mammals, and is located at the front of each cerebral hemisphere. It is parted from the parietal lobe by a groove between tissues called the central sulcus and from the temporal lobe by a deeper groove called the lateral sulcus. The most anterior rounded part of the frontal lobe is known as the frontal pole, one of the three poles of the cerebrum.

<span class="mw-page-title-main">Rhinencephalon</span>

In animal anatomy, the rhinencephalon, also called the smell-brain or olfactory brain, is a part of the brain involved with smell. It forms the paleocortex and is rudimentary in the human brain.

<span class="mw-page-title-main">Internal capsule</span> White matter structure situated in the inferomedial part of each cerebral hemisphere of the brain

The internal capsule is a white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain. It carries information past the basal ganglia, separating the caudate nucleus and the thalamus from the putamen and the globus pallidus. The internal capsule contains both ascending and descending axons, going to and coming from the cerebral cortex. It also separates the caudate nucleus and the putamen in the dorsal striatum, a brain region involved in motor and reward pathways.

<span class="mw-page-title-main">Olfactory system</span> Sensory system used for smelling

The olfactory system or sense of smell is the sensory system used for smelling (olfaction). Olfaction is one of the special senses, that have directly associated specific organs. Most mammals and reptiles have a main olfactory system and an accessory olfactory system. The main olfactory system detects airborne substances, while the accessory system senses fluid-phase stimuli.

<span class="mw-page-title-main">Lateral ventricles</span> Two largest ventricles in each cerebral hemisphere

The lateral ventricles are the two largest ventricles of the brain and contain cerebrospinal fluid. Each cerebral hemisphere contains a lateral ventricle, known as the left or right lateral ventricle, respectively.

<span class="mw-page-title-main">Precentral gyrus</span> Motor gyrus of the posterior frontal lobe of the brain

The precentral gyrus is a prominent gyrus on the surface of the posterior frontal lobe of the brain. It is the site of the primary motor cortex that in humans is cytoarchitecturally defined as Brodmann area 4.

<span class="mw-page-title-main">Middle cerebral artery</span> Paired artery that supplies blood to the cerebrum

The middle cerebral artery (MCA) is one of the three major paired cerebral arteries that supply blood to the cerebrum. The MCA arises from the internal carotid artery and continues into the lateral sulcus where it then branches and projects to many parts of the lateral cerebral cortex. It also supplies blood to the anterior temporal lobes and the insular cortices.

<span class="mw-page-title-main">Lobes of the brain</span> Parts of the cerebrum

The lobes of the brain are the major identifiable zones of the human cerebral cortex, and they comprise the surface of each hemisphere of the cerebrum. The two hemispheres are roughly symmetrical in structure, and are connected by the corpus callosum. They traditionally have been divided into four lobes, but are today considered as having six lobes each. The lobes are large areas that are anatomically distinguishable, and are also functionally distinct to some degree. Each lobe of the brain has numerous ridges, or gyri, and furrows, the sulci that constitute further subzones of the cortex. The expression "lobes of the brain" usually refers only to those of the cerebrum, not to the distinct areas of the cerebellum.

<span class="mw-page-title-main">Posterior cerebral artery</span> Artery which supplies blood to the occipital lobe of the brain

The posterior cerebral artery (PCA) is one of a pair of cerebral arteries that supply oxygenated blood to the occipital lobe, part of the back of the human brain. The two arteries originate from the distal end of the basilar artery, where it bifurcates into the left and right posterior cerebral arteries. These anastomose with the middle cerebral arteries and internal carotid arteries via the posterior communicating arteries.

<span class="mw-page-title-main">Orbitofrontal cortex</span> Region of the prefrontal cortex of the brain

The orbitofrontal cortex (OFC) is a prefrontal cortex region in the frontal lobes of the brain which is involved in the cognitive process of decision-making. In non-human primates it consists of the association cortex areas Brodmann area 11, 12 and 13; in humans it consists of Brodmann area 10, 11 and 47.

<span class="mw-page-title-main">Uncus</span> Structure in the brain

The uncus is an anterior extremity of the parahippocampal gyrus. It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis.

<span class="mw-page-title-main">Diagonal band of Broca</span>

The diagonal band of Broca interconnects the amygdala and the septal area. It is one of the olfactory structures. It is situated upon the inferior aspect of the brain. It forms the medial margin of the anterior perforated substance.

The amygdalofugal pathway is one of the three major efferent pathways of the amygdala, meaning that it is one of the three principal pathways by which fibers leave the amygdala. It leads from the basolateral nucleus and central nucleus of the amygdala. The amygdala is a limbic structure in the medial temporal lobe of the brain. The other main efferent pathways from the amygdala are the stria terminalis and anterior commissure.

<span class="mw-page-title-main">Anterior perforated substance</span> Part of the brain

The anterior perforated substance is a part of the brain. It is bilateral. It is irregular and quadrilateral. It lies in front of the optic tract and behind the olfactory trigone.

The sensory cortex can refer informally to the primary somatosensory cortex, or it can be used as a term for the primary and secondary cortices of the different senses : the visual cortex on the occipital lobes, the auditory cortex on the temporal lobes, the primary olfactory cortex on the uncus of the piriform region of the temporal lobes, the gustatory cortex on the insular lobe, and the primary somatosensory cortex on the anterior parietal lobes. Just posterior to the primary somatosensory cortex lies the somatosensory association cortex, which integrates sensory information from the primary somatosensory cortex to construct an understanding of the object being felt. Inferior to the frontal lobes are found the olfactory bulbs, which receive sensory input from the olfactory nerves and route those signals throughout the brain. Not all olfactory information is routed to the olfactory cortex: some neural fibers are routed to the supraorbital region of the frontal lobe, while others are routed directly to limbic structures. The direct limbic connection makes the olfactory sense unique.

<span class="mw-page-title-main">Straight gyrus</span>

The portion of the inferior frontal lobe immediately adjacent to the longitudinal fissure is named the straight gyrus,(or gyrus rectus) and is continuous with the superior frontal gyrus on the medial surface.

<span class="mw-page-title-main">Pallium (neuroanatomy)</span> Layers of grey and white matter that cover the upper surface of the cerebrum in vertebrates

In neuroanatomy, pallium refers to the layers of grey and white matter that cover the upper surface of the cerebrum in vertebrates. The non-pallial part of the telencephalon builds the subpallium. In basal vertebrates, the pallium is a relatively simple three-layered structure, encompassing 3–4 histogenetically distinct domains, plus the olfactory bulb.

<span class="mw-page-title-main">Orbital gyri</span>

The inferior or orbital surface of the frontal lobe is concave, and rests on the orbital plate of the frontal bone. It is divided into four orbital gyri by a well-marked H-shaped orbital sulcus. These are named, from their position, the medial, anterior, lateral, and posterior, orbital gyri. The medial orbital gyrus presents a well-marked antero-posterior sulcus, the olfactory sulcus, for the olfactory tract; the portion medial to this is named the straight gyrus, and is continuous with the superior frontal gyrus on the medial surface.

References

  1. 1 2 3 4 De Cannière, G., « The olfactory striae: A historical perspective on the inconsistent anatomy of the bulbar projections », Journal of Anatomy, no 244,‎ 2024, p. 170–183, Available from: https://doi.org/10.1111/joa.13952
  2. 1 2 Heimer, L., « Olfactory projections to the diencephalon », Int. Conf. Neurobiology of CNS-­Hormone Interactions, Chapel Hill: Anatomical Neuroendocrinology,‎ 1974, p. 30–­39
  3. Carpenter, Malcolm B. (1985). Core text of neuroanatomy (3rd ed.). Baltimore: Williams & Wilkins. p. 29. ISBN   0683014552.
  4. Allison, A. C. (1954). "The secondary olfactory areas in the human brain". Journal of Anatomy, 88 (Pt 4), 481–488.2.
  5. Purves, Dale (2012). Neuroscience (5th ed.). Sunderland, Mass. p. 515. ISBN   9780878936953.{{cite book}}: CS1 maint: location missing publisher (link)
  6. "Kallmann syndrome". Genetics Home Reference. US Library of Medicine. National Institutes for Health. Genetic and Rare Diseases Information. June 26, 2016. Retrieved November 15, 2021.
  7. Huart, C.; Meusel, T.; Gerber, J.; Duprez, T.; Rombaux, P.; Hummel, T. (November 2011). "The Depth of the Olfactory Sulcus Is an Indicator of Congenital Anosmia". American Journal of Neuroradiology. 32 (10): 1911–1914. doi: 10.3174/ajnr.A2632 . PMC   7966015 . PMID   21868619.

PD-icon.svgThis article incorporates text in the public domain from page 826 of the 20th edition of Gray's Anatomy (1918)