Olfactory tract#Structure

{{Infobox brain

| Name = Olfactory tract

| Latin = tractus olfactorius

| Image = Cerebral Gyri - Inferior Surface2.png

| Caption = Olfactory peduncle lying in olfactory sulcus and olfactory striae labelled (anterior at top)

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|System=Olfactory system|Function=|Location=Brain}}

The olfactory tract (olfactory peduncle or 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.

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).{{Cite journal |last=De Cannière |first=Gilles |date=January 2024 |title=The olfactory striae: A historical perspective on the inconsistent anatomy of the bulbar projections |journal=Journal of Anatomy |language=en |volume=244 |issue=1 |pages=170–183 |doi=10.1111/joa.13952 |issn=0021-8782 |pmc=10734660 |pmid=37712100|pmc-embargo-date=15 September 2025 }} However, the existence of the medial olfactory tract (and consequently the medial stria) is controversial in primates (including humans).{{Cite book |title=Anatomical Neuroendocrinology: Based on the International Conference on Neurobiology of CNS-Hormone Interactions, Chapel Hill, N.C., May 1974 |date=23 July 1976 |publisher=S. Karger AG |isbn=978-3-8055-2154-3 |editor-last=Stumpf |editor-first=W.E. |pages=30–39 |language=en |chapter=Olfactory Projections to the Diencephalon |doi=10.1159/000398021 |editor-last2=Grant |editor-first2=L.D.}}

Structure

The olfactory peduncle and olfactory bulb lie in the olfactory sulcus{{cite book |last1=Carpenter |first1=Malcolm B. |title=Core text of neuroanatomy |date=1985 |publisher=Williams & Wilkins |location=Baltimore |isbn=0683014552 |page=29 |edition=3rd}} 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.{{Cite journal |last=Allison |first=A. C. |date=October 1954 |title=The secondary olfactory areas in the human brain |journal=Journal of Anatomy |volume=88 |issue=4 |pages=481–488 |issn=0021-8782 |pmc=1244658 |pmid=13211468}}

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.

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. The medial olfactory stria is now described as terminating much more medially, in the ventral tenia tecta.

=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.

=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.{{cite book |last1=Purves |first1=Dale |title=Neuroscience |date=2012 |location=Sunderland, Mass. |isbn=9780878936953 |page=515 |edition=5th}}{{cite web|url=https://ghr.nlm.nih.gov/condition/kallmann-syndrome |title=Kallmann syndrome |date=26 June 2016 |website=Genetics Home Reference. US Library of Medicine |publisher=National Institutes for Health. Genetic and Rare Diseases Information |access-date=15 November 2021}} The depth of the olfactory sulcus is an indicator of such congenital anosmia.{{cite journal|first1=C. |last1=Huart|first2=T. |last2=Meusel|first3= J.|last3= Gerber|first4=T. |last4=Duprez|first5= P. |last5=Rombaux |first6= T. |last6=Hummel|title=The Depth of the Olfactory Sulcus Is an Indicator of Congenital Anosmia|journal=American Journal of Neuroradiology|volume=32|issue=10|pages=1911–1914|date=November 2011|doi=10.3174/ajnr.A2632|pmid=21868619|pmc=7966015|doi-access=free}}

Additional images

File:Gray732.png|Scheme of rhinencephalon. (Olfactory tract visible at left.)

File:Gray724.png|Base of brain.

File:Gray772.png|Plan of olfactory neurons.

File:Gray729 olfactory sulcus.png|Orbital surface of frontal lobe olfactory sulcus shown in red.

References

External links

{{cite web|url=http://www.yale.edu/cnerves/cn1/cn1_4.html|title=1–4|publisher=Yale School of Medicine|work=Cranial Nerves|archive-url=https://web.archive.org/web/20160303222022/http://www.yale.edu/cnerves/cn1/cn1_4.html|archive-date=3 March 2016}}

Category:Olfactory system