olfactory epithelium

Forebrain > olfactory epithelium

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Schematic showing the position of the olfactory epithelium in sagittal, horizontal and coronal sections through the zebrafish brain. Based on the anatomical segmentation of 3 day old zebrafish larval brain by Thomas Müller, Olaf Ronneberger, Wolfgang Driever and colleagues. For details see Ronneberger et al., Nat. Meth. 2012 and http://vibez.informatik.uni-freiburg.de

Abbreviations: Ce, cerebellar plate; D, dorsal telencephalon/pallium; E, epiphysis; EmT, eminentia thalami; Hb, habenula; Hyp, hypothalamus; MO, medulla oblongata; OB, olfactory bulb; OT, optic tectum; PG, preglomerular complex; PO, preoptic area;PrT, pretectum; PTd, posterior tuberculum dorsal part; PTh, prethalamus; PTv posterior tuberculum ventral part; Teg, tegmentum; Th, thalamus; TS, torus semicircularis; V, ventral telencephalon/subpallium; Va, valvula cerebelli.

Description

Also known as the nasal placode. The olfactory epithelium contains the cell bodies of olfactory sensory neurons that project axons into the olfactory bulb where they contact mitral cells at olfactory bulb glomeruli. In zebrafish the predominant subtypes are ciliated sensory neurons that have long dendrites and microvillous sensory neurons, which have short dendrites, these cells are placodally derived (Aguillon et al., 2018). A third group of neurons associated with the olfactory epithelium express gonadotropin releasing hormone 3 (Gnrh3), these may be the cell bodies of the terminal nerve cranial nerve 0.

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Ontology
 

is part of: olfactory system

has parts:

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ZFIN

OLS Tree Diagram

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Anatomical segmentation of 3 day old zebrafish larval brain by Thomas Müller, Olaf Ronneberger, Wolfgang Driever and colleagues. For details see Ronneberger et al., Nat. Meth. 2012 and http://vibez.informatik.uni-freiburg.de

Transgenic Lines that label this brain region

Antibodies that label this brain region

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Key Publications

Anne Hansen, Zeiske Eckart
The Peripheral Olfactory Organ of the Zebrafish, Danio rerio: an Ultrastructural Study
Chemical Senses, Volume 23, Issue 1, February 1998, Pages 39-48, https://doi.org/10.1093/chemse/23.1.39

Kathleen E. Whitlock and Monte Westerfield
A Transient Population of Neurons Pioneers the Olfactory Pathway in the Zebrafish
Journal of Neuroscience 1 November 1998, 18 (21) 8919-8927; DOI: https://doi.org/10.1523/JNEUROSCI.18-21-08919.1998

Raphaël Aguillon, Julie Batut, Arul Subramanian, Romain Madelaine, Pascale Dufourcq, Thomas F Schilling, Patrick Blader
Cell-type heterogeneity in the early zebrafish olfactory epithelium is generated from progenitors within preplacodal ectoderm
eLife 2018;7:e32041 DOI: 10.7554/eLife.32041

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olfactory bulb

Forebrain > Telencephalon > Olfactory Bulb

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Schematic showing the position of the olfactory bulbs in sagittal, horizontal and coronal sections through the zebrafish brain. Based on the anatomical segmentation of 3 day old zebrafish larval brain by Thomas Müller, Olaf Ronneberger, Wolfgang Driever and colleagues. For details see Ronneberger et al., Nat. Meth. 2012 and http://vibez.informatik.uni-freiburg.de

Abbreviations: Ce, cerebellar plate; D, dorsal telencephalon/pallium; E, epiphysis; EmT, eminentia thalami; Hb, habenula; Hyp, hypothalamus; MO, medulla oblongata; OB, olfactory bulb; OT, optic tectum; PG, preglomerular complex; PO, preoptic area;PrT, pretectum; PTd, posterior tuberculum dorsal part; PTh, prethalamus; PTv posterior tuberculum ventral part; Teg, tegmentum; Th, thalamus; TS, torus semicircularis; V, ventral telencephalon/subpallium; Va, valvula cerebelli.

Description

In the adult, the olfactory bulbs are paired protrusions in the anteriormost region of the telencephalon. They recieve primary sensory input from the olfactory epithelium directly via the olfactory nerve (Cranial nerve I). Cytoarchitecturally the bulb is arranged into four concentric layers.

Lateral view of a 5dpf zebrafish brain labelled with SV2 and tubulin antibodies showing olfactory nerve(blue) and glomeruli (pink).

Frontal view of 4dpf zebrafish labelled with anti-tubulin showing the olfactory nerve emanating from the olfactory epithelium and entering the bulb where individual olfactory sensory neurons contact individual olfactory glomeruli.

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Neuroanatomy

In the olfactory bulb there are three main cell types: mitral cells, ruffed cells and granule cells.  In addition to these there is also a population of catchecholaminergic cells that are often referred to as either juxtaglomerular or periglomerular cells (Byrd and Brunjes, 1995; Fuller et al., 2005 and 2006)).  

In the mature olfactory bulb, the different cell types that form the olfactory bulb are organised into four concentric layers (from external to internal layers).

1) The Primary Olfactory Fiber Layer (OFL)

This is the outermost layer of the olfactory bulb and contains axon terminals of the olfactory sensory neurons (OSNs).  Each of these OSNs expresses a single olfactory receptor (OR) on its surface in the olfactory epithelium.  An enormous array of odorants can be detected by the large repertoire of different ORs expressed by OSNs (Sato et al., 2007).  The axons of the OSNs come together and fasciculate to form the olfactory nerve (Cranial Nerve I) that projects into the olfactory bulb.  Once inside the bulb the olfactory nerve axons defasciculate and spread over the glomerular layer of the olfactory bulb to form the outer layer of primary olfactory afferents.

 2) The Glomerular Layer (GL)

Primary olfactory afferents branch conspicuously and synapse onto the dendrites of the mitral cells to form a specialised spherical structure named an olfactory glomerulus. The layer containing all these olfactory glomeruli is known as the glomerular layer.

 3) The Mitral or External Cellular Layer (MCL)

The Mitral or External Cellular layer is formed mainly by mitral cells, although ruffed cells can also be found in this layer (Fuller et al., 2005 and 2006).  Both cell types are projection neurons and use glutamate as a neurotransmitter.  In fish, individual mitral cells project several dendrites onto multiple glomeruli, whereas in mammals, single mitral cells project a primary dendrite onto a single glomerulus. Thus, a single fish mitral cell receives sensory information from several different odorant receptors (Yoshihara et al, 2001). 

The apical dendrites of the mitral cells ramify and establish synaptic contact with axons of olfactory receptors to form the olfactory glomeruli. Their axons project via the lateral and medial olfactory tracts to bilaterally symmetric fields within the telencephalic lobes. These telencephalic regions are interconnected by mitral cell axonal processes that project through the anterior commissure. The fasciculated axons of the mitral cells extend posteriorly and dorsally to the habenula via the stria medularis where they cross to the contralateral side via the habenula commisure (Miyasaka, 2009). Some of these axons asymmetrically innervate the medial portion of the central neuropil domain of the right habenula.  These mitral cells are labelled in the transgenic line Tg(lhx2A:GapYFP) (Miyasaka et al, 2009).

 Ruffed cells are less numerous than mitral cells.  Ruffed cells have short collaterals in the proximal region of their axon, which gives these cells their characteristic appearance (Fuller et al., 2005).

4) The Granule or Internal Cellular layer (GCL)

The Granule cell layer or Internal Cellular layer is mainly composed of granule cells, which act as interneurons in the olfactory bulb circuitry.  These cells have apical dendrites that contact mitral and ruffed cells, while their basal dendrites contact axons originating from extrabulbar regions.  They express the neurotransmitter gamma-aminobutyric acid (GABA). 

A subpopulation of granule cells produce catecholamines and are tyrosine hydroxylase positive.  These cells are referred to as juxtaglomerular, periglomerular or perinest cells (Byrd and Brunjes, 1995; Fuller et al., 2005 and 2006).

The adult zebrafish OB contains another subset of neuroendocrine cells that express Gonadotrophin releasing hormone(GnRH). These cells are known as terminal nerve cells.  These neurons are born near to the olfactory epithelium and then migrate along the axons of the olfactory sensory neurons to populate the bulb (Whitlock et al., 2003; Palevitch et al., 2007).

Schematic of olfactory bulb cytoarchitecture

abbreviations: GC granule cell; GL glomerular layer; ICL inner cellular layer; MC mitral cell;MCL mitral cell layer; NI cranial nerve I/olfactory nerve; ONL outer layer of primary olfactory afferents; OSN olfactory sensory neuron; PC periglomerular cell.

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Development

The olfactory bulbs along with the rest of the telencephalic lobes originate from the anterior neural plate.

At 1dpf and 2dpf, the prospective olfactory bulb is located in a dorsoposterior region of the telencephalon, adjacent to the diencephalon. From 2dpf to 5dpf, an anterior morphogenetic movement brings the olfactory bulb rostrally to its characteristic position as the anteriormost structure of the brain and away from the diencephalon.

By 2dpf all major neuronal types are present and have elaborated processes so that a number of glomeruli can also be seen.

Cartoon showing the position of the olfactory bulb at three different stages of the zebrafish development (2dpf, 3dpf and 5dpf). The olfactory bulb is located in a dorso-posterior position in the telencephalon at 2dpf, but later in development (5dpf) acquires its characteristic anterior position.

olfactory bulb schematic lateral 4dpf

Lateral key: At this stage of development (4dpf) The paired olfactory bulbs are the most anterior region of the telencephalon. The olfactory bulbs are involved in olfaction and the detection of odours.

Olfactory bulb dorsal schematic 4dpf

Dorsal key: At this stage of development(4dpf) The paired olfactory bulbs are the most anterior region of the telencephalon. The olfactory bulbs are involved in olfaction and the detection of odours.

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Ontology
 

is part of: telencephalon

has parts: external cellular layer, glomerular layer, internal cellular layer, primary olfactory fiber layer

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ZFIN

OLS Tree Diagram

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Transgenic Lines that label this brain region

Antibodies that label this brain region

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Key Publications

Miyasaka, N., Morimoto, K., Tsubokawa, T., Higashijima, S., Okamoto, H., and Yoshihara, Y. (2009)
From the olfactory bulb to higher brain centers: genetic visualization of secondary olfactory pathways in zebrafish.
The Journal of neuroscience 29(15):4756-4767.

Miyasaka, N., Wanner, A.A., Li, J., Mack-Bucher, J., Genoud, C., Yoshihara, Y., and Friedrich, R.W. (2013)
Functional development of the olfactory system in zebrafish.
Mechanisms of Development. 130(6-8):336-46.

Miyasaka, N., Arganda-Carreras, I., Wakisaka, N., Masuda, M., Sümbül, U., Seung, H.S., Yoshihara, Y. (2014)
Olfactory projectome in the zebrafish forebrain revealed by genetic single-neuron labelling. Nature communications. 5:3639.

Miyasaka, N., Sato, Y., Yeo, S.Y., Hutson, L.D., Chien, C.B., Okamoto, H., and Yoshihara, Y. (2005) Robo2 is required for establishment of a precise glomerular map in the zebrafish olfactory system.
Development (Cambridge, England). 132(6):1283-1293.

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pallium/ dorsal telencephalon

Forebrain > Telencephalon > Pallium

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Schematic showing the position of the pallium in sagittal, horizontal and coronal sections through the zebrafish brain.
Based on the anatomical segmentation of 3 day old zebrafish larval brain by Thomas Müller, Olaf Ronneberger, Wolfgang Driever and colleagues. For details see Ronneberger et al., Nat. Meth. 2012 and http://vibez.informatik.uni-freiburg.de

Abbreviations: Ce, cerebellar plate; D, dorsal telencephalon/pallium; E, epiphysis; EmT, eminentia thalami; Hb, habenula; Hyp, hypothalamus; MO, medulla oblongata; OB, olfactory bulb; OT, optic tectum; PG, preglomerular complex; PO, preoptic area;PrT, pretectum; PTd, posterior tuberculum dorsal part; PTh, prethalamus; PTv posterior tuberculum ventral part; Teg, tegmentum; Th, thalamus; TS, torus semicircularis; V, ventral telencephalon/subpallium; Va, valvula cerebelli.

Description

The Pallium is a dorsal division of the Telencephalon (also called the dorsal telencephalon). The pallium is generally subdivided in a number of areas, named by their topographical position within the telencephalon (Dm, Dd, Dl, Dc and Dp) (see Wullimann et al., 1996). Although projection neurons of the olfactory bulb are pallial derivatives, the olfactory bulb is considered as a separate structure and it is described in its own section (see olfactory bulb).

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Ontology
 

is part of: telencephalon

has parts: dorsal zone (Dd), central zone (Dc), medial zone (Dm), caudal/posterior zone (Dp), lateral zone (Dl).

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ZFIN

OLS Tree Diagram

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Anatomical segmentation of 3 day old zebrafish larval brain by Thomas Müller, Olaf Ronneberger, Wolfgang Driever and colleagues. For details see Ronneberger et al., Nat. Meth. 2012 and http://vibez.informatik.uni-freiburg.de

Transgenic Lines that label this brain region

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Antibodies that label this brain region

Key Publications

Turner KJ, Hawkins TA, Henriques PM, Valdivia LE, Bianco IH, Wilson SW and Folgueira M (2022)
A Structural Atlas of the Developing Zebrafish Telencephalon Based on Spatially-Restricted Transgene Expression.
Front. Neuroanat. 16:840924. doi: 10.3389/fnana.2022.840924

Folgueira M, Bayley P, Navratilova P, Becker TS, Wilson SW, Clarke JD. (2012)
Morphogenesis underlying the development of the everted teleost telencephalon.
Neural Dev. 2012;7:32.

Wullimann, M.F., Rupp, B., Reichert, H., and eds. (1996)
Neuroanatomy of the Zebrafish Brain. A Topological Atlas.
Basel, Switzerland: Basel, Switzerland: Birkhäuser Verlag. :160 p.

Mueller, T., Dong, Z., Berberoglu, M.A., and Guo, S. (2011)
The dorsal pallium in Zebrafish, Danio rerio (Cyprinidae, Teleostei).
Brain research. 1381:95-105.

Ganz, J., Kroehne, V., Freudenreich, D., Machate, A., Geffarth, M., Braasch, I., Kaslin, J., Brand, M. (2014) Subdivisions of the adult zebrafish pallium based on molecular marker analysis.
F1000Research. 3:308.

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eminentia thalami/ thalamic eminence

Forebrain > Diencephalon> Eminentia Thalami

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Schematic showing the position of the thalamic eminence in sagittal, horizontal and coronal sections through the zebrafish brain.
Based on the anatomical segmentation of 3 day old zebrafish larval brain by Thomas Müller, Olaf Ronneberger, Wolfgang Driever and colleagues. For details see Ronneberger et al., Nat. Meth. 2012 and http://vibez.informatik.uni-freiburg.de

Abbreviations: Ce, cerebellar plate; D, dorsal telencephalon/pallium; E, epiphysis; EmT, eminentia thalami; Hb, habenula; Hyp, hypothalamus; MO, medulla oblongata; OB, olfactory bulb; OT, optic tectum; PG, preglomerular complex; PO, preoptic area;PrT, pretectum; PTd, posterior tuberculum dorsal part; PTh, prethalamus; PTv posterior tuberculum ventral part; Teg, tegmentum; Th, thalamus; TS, torus semicircularis; V, ventral telencephalon/subpallium; Va, valvula cerebelli.

Description

The thalamic eminence is part of the diencephalon and lies ventral to the ventral thalamus and dorsal to the preoptic area. This region gives rise to the ventral entopeduncular nucleus that extends into the telencephalon and straddles the diencephalic/telencephalic border. The ventral entopeduncular nucleus is a major afferent nucleus to the habenulae. 

Schematic adapted from Mueller 2012 showing the nuclei that comprise the wider thalamus. 

Abbreviations: A, anterior thalamic nucleus; CPo, centroposterior thalamic nucleus; D, dorsal telencephalon (pallium); DP, dorsoposterior thalamic nucleus; EmT, eminentia thalami; Hyp, hypothalamus; Hb, habenula; I, intermediate thalamic nucleus; IC, intercalated thalamic nucleus; OB, olfactory bulb; OT, optic tectum; P, posterior thalamic (preglomerular) nucleus; PG, preglomerular complex; PGa, anterior preglomerular nucleus; PGc, caudal preglomerular nucleus; PGl, lateral preglomerular nucleus; PGm, medial preglomerular nucleus; PO, preoptic region; PrT, pretectum; PVO, paraventricular organ; SG, subglomerular nucleus; TGN, tertiary gustatory nucleus; TPp, periventricular nucleus of posterior tuberculum; TPm, migrated nucleus of posterior tuberculum; V,ventral telencephalon (subpallium); VL, ventrolateral thalamic nucleus; VM, ventromedial thalamic nucleus.

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Ontology
 

is part of: forebrain

has parts:

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ZFIN

OLS Tree Diagram

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Anatomical segmentation of 3 day old zebrafish larval brain by Thomas Müller, Olaf Ronneberger, Wolfgang Driever and colleagues. For details see Ronneberger et al., Nat. Meth. 2012 and http://vibez.informatik.uni-freiburg.de

Transgenic Lines that label this brain region

Antibodies that label this brain region

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Key Publications

Turner KJ., et al.
Afferent Connectivity of the Zebrafish Habenulae.
Front Neural Circuits. 2016 Apr 26;10:30. doi: 10.3389/fncir.2016.00030

Wullimann, M.F. & Mueller, T., 2004a. 
Identification and morphogenesis of the eminentia thalami in the zebrafish. 
Journal of Comparative Neurology, 471(1), pp.37–48.

Mueller, T., 2012. 
What is the thalamus in zebrafish?
Frontiers in Neuroscience,6. pp.1–14.

Mueller T, Guo S.
The distribution of GAD67-mRNA in the adult zebrafish (teleost) forebrain reveals a prosomeric pattern and suggests previously unidentified homologies to tetrapods. 
The Journal of comparative neurology. 2009;516(6):553-568. doi:10.1002/cne.22122.

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telencephalon

Forebrain > Telencephalon

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Description
 

Formed from the rostral-most neuromere, the telencephalon in zebrafish consists of the olfactory bulbs, dorsal telencephalon or pallium and the ventral telencephalon or subpallium.   The teleost telencephalon is formed by two solid telencephalic lobes separated by a T-shaped ventricle. This "everted" morphology is in contrast with most other vertebrates where the telencephalon forms by a process of evagination resulting in hollow telencephalic lobes surrounding a central ventricle.    

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Ontology
 

is part of: forebrain

has parts: dorsal telencephalon, olfactory bulb, telencephalic ventricle, telencephalic white matter, ventral telencephalon. 

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ZFIN

OLS Tree Diagram

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Transgenic Lines that label this brain region

Antibodies that label this brain region

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Key Publications

Folgueira M, Bayley P, Navratilova P, Becker TS, Wilson SW, Clarke JD.
Morphogenesis underlying the development of the everted teleost telencephalon. 
Neural Development. 2012;7:32. doi:10.1186/1749-8104-7-32.

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subpallium/ ventral telencephalon

Forebrain > Telencephalon > Subpallium

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Schematic showing the position of the subpallium in sagittal, horizontal and coronal sections through the zebrafish brain.

Based on the anatomical segmentation of 3 day old zebrafish larval brain by Thomas Müller, Olaf Ronneberger, Wolfgang Driever and colleagues. For details see Ronneberger et al., Nat. Meth. 2012 and http://vibez.informatik.uni-freiburg.de

Abbreviations: Ce, cerebellar plate; D, dorsal telencephalon/pallium; E, epiphysis; EmT, eminentia thalami; Hb, habenula; Hyp, hypothalamus; MO, medulla oblongata; OB, olfactory bulb; OT, optic tectum; PG, preglomerular complex; PO, preoptic area;PrT, pretectum; PTd, posterior tuberculum dorsal part; PTh, prethalamus; PTv posterior tuberculum ventral part; Teg, tegmentum; Th, thalamus; TS, torus semicircularis; V, ventral telencephalon/subpallium; Va, valvula cerebelli.

Description

The ventral telencephalon or subpallium is a ventral division of the Telencephalic Lobes. The subpallium is generally subdivided in a number of areas named by their topographical position in the telencephalon (Vd, Vv, Vc, Vl, Vs and Vp).

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Ontology
 

is part of: forebrain, telencephalon

has parts:

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ZFIN

OLS Tree Diagram

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Transgenic lines that label this brain region

Antibodies that label this brain region

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Key Publications

Ganz, J., Kaslin, J., Freudenreich, D., Machate, A., Geffarth, M., and Brand, M. (2012)
Subdivisions of the adult zebrafish subpallium by molecular marker analysis.
The Journal of comparative neurology. 520(3):633-55.

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