The main subdivisions of the embryogenesis | embryonic vertebrate brain, which later differentiate into the forebrain, midbrain and hindbrain

In its earliest form, the brain appears as three swellings at the front end of the neural tube ; these swellings eventually become the forebrain, midbrain, and hindbrain ( the prosencephalon, mesencephalon, and rhombencephalon, respectively ).

The front end of the nerve tube is expanded by a thickening of the walls and expansion of the central canal of spinal cord into three primary brain vesicles: The prosencephalon ( forebrain ), mesencephalon ( midbrain ) and rhombencephalon ( hindbrain ), further differentiated in the various vertebrate groups.

However, the situation is more complex, since comparative embryology shows that the length axis of the neural tube ( the primordium of the brain ) has three internal bending points, namely two ventral bendings at the cervical and cephalic flexures ( cervical flexure roughly between the medulla oblongata and the spinal cord, and cephalic flexure between the diencephalon and the midbrain ), and a dorsal ( pontine or rhombic ) flexure at the midst of the hindbrain, behind the cerebellum.

The prosencephalon, the mesencephalon ( midbrain ), and rhombencephalon ( hindbrain ) are the three primary portions of the brain during early development of the central nervous system.

The midbrain is located below the cerebral cortex, and above the hindbrain placing it near the center of the brain.

As a vertebrate brain, the human brain has the properties that are common to all vertebrate brains, including a basic division into three parts called the forebrain, midbrain, and hindbrain, each with fluid-filled ventricles at their core, and a set of generic vertebrate brain structures including the medulla oblongata, pons, cerebellum, optic tectum, thalamus, hypothalamus, basal ganglia, olfactory bulb, and many others.

“ Fibroblast growth factor receptors cooperate to regulate neural progenitor properties in the developing midbrain and hindbrain .” The Journal of Neuroscience, 17, 8581-8592.

“ FGF signaling pathways in development of the midbrain and anterior hindbrain .” Journal of Neurochemistry, 101, 1185-1193.

In the human embryo eight rhombomeres can be distinguished, from caudal to rostral: Rh7-Rh1 and the isthmus ( a borderline between midbrain and hindbrain in the most rostral part of the rhombomeres ).

The hindbrain, for example, is patterned by Hox genes, which are expressed in overlapping domains along the anteroposterior axis under the control of retinoic acid.

The 3 ' genes in the Hox cluster are induced by retinoic acid in the hindbrain, whereas the 5 ' Hox genes are not induced by retinoic acid and are expressed more posteriorly in the spinal cord.

One of the peculiarities of Lumpsuckers neural system is that they lack Mauthner cell neurons in their hindbrain, while these cells are present in virtually all other teleost fish.

For example, one study showed that there are proteins called Gli1, Gli2, and Gli3 that affect ventral hindbrain development, and are also required for motoneuron development and correct neural patterning in the hindbrain.

Neurons that form the facial nucleus are produced in r4, but move along the anteroposterior axis of the hindbrain into r6, after which they move dorsolaterally.

From this one can conclude that multiple subclasses of motor neurons are produced in specific locations in the developing hindbrain.

Rhombomeres are such segments that make up the rhombencephalon or hindbrain.

The symptoms are caused by a genetic mutation that results in an expansion of abnormal " CAG " trinucleotide repeats in the ATXN3 gene that results in degeneration of cells in the hindbrain.

There are also high levels of aromatase, an estrogen-generating enzyme, in the hindbrain vocal motor region.

It was found in one study that reticular neurons in the lamprey hindbrain, which included isthmic, bulbar, and Mauthner cells, developed in conserved rhombomere-specific positions, similar to those in the zebrafish.

Nevertheless, the lumpsuckers do have a C-startle response, which is apparently mediated by other hindbrain cells.

Later on in development, rhombomeres form the rhombocephalon, which forms the hindbrain in vertebrates.

The rhombencephalon ( or hindbrain ) is a developmental categorization of portions of the central nervous system in vertebrates.

Above the mesencephalon is the prosencephalon ( future forebrain ) and beneath it is the rhombencephalon ( future hindbrain ).

Anatomists classify the cerebellum as part of the metencephalon, which also includes the pons ; the metencephalon is the upper part of the rhombencephalon or " hindbrain ".

Signals that control anteroposterior neural development include FGF and retinoic acid which act in the hindbrain and spinal cord.

The myelencephalon develops from the primary vesicular structure called the rhombencephalon ( or hindbrain ), which is present in all vertebrate embryos.

The neuronal pathway for midshipman vocalization starts at the ventral medullary nucleus and continues to a hindbrain vocal pattern generator, which contains both pre-pacemaker and pacemaker nuclei.

It is also important to understand the role of birth defects in the development of hindbrain malformations that can lead to syringomyelia.

In the vertebrate embryo, a rhombomere is a transiently divided segment of the developing neural tube, within the hindbrain region ( a neuromere ) in the area that will eventually become the rhombencephalon.

This shows that Gli2 performs different functions in the hindbrain that Gli3 is unable to substitute.

While the hindbrain is developing, trigeminal cell bodies have been shown to migrate dorsolaterally within rhombomeres 2 and 3, while facial cells move dorsolaterally into r5 near the pial surface.

The hindbrain is homologous to a part of the arthropod brain known as the sub-oesophageal ganglion.

The duration of calls is controlled by the pre-pacemaker neurons in the hindbrain.

Gli2 and Gli3 in a developing hindbrain also have distinct functions in the Shh ( sonic hedgehog ) signal transduction.

Further studies. showed that this model when combined with a lumbar spinal cord myelotomy leads to the hindbrain herniation characteristic of the Chiari II malformation and that in utero surgery restores normal hindbrain anatomy by stopping the leak of cerebrospinal fluid through the myelomeningocele lesion.

As compared with the open fetal surgery technique, fetoscopic repair of myelomeningocele has resulted in higher rates of fetal death, premature rupture of membranes, chorioamnionitis, oligohydramnios, premature delivery, and persistent hindbrain herniation.

The Austrian pathologist Hans Chiari in the late 19th century described seemingly related anomalies of the hindbrain, the so called Chiari malformations I, II and III.

The pons and the hindbrain ( rhombencephalon ) lie caudally to the VTA.

Many of the mature hindbrain nuclei can occupy either one or several rhombomere-derived regions.

The conclusion drawn was that segmentation of the hindbrain contributes to the way axons project within the vestibular complex.

Studies have shown that the number of neurons in the hindbrain increase as a species evolves.