A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. The brain is the largest cluster of neuron somata in the body and is typically located in the head, usually near organs for special senses such as vision, hearing and olfaction. It is the most specialized and energy-consuming organ in the body, responsible for complex sensory perception, motor control, endocrine regulation and the development of intelligence.
The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consisting of the allocortex. It is separated into two cortices, by the longitudinal fissure that divides the cerebrum into the left and right cerebral hemispheres. The two hemispheres are joined beneath the cortex by the corpus callosum. The cerebral cortex is the largest site of neural integration in the central nervous system. It plays a key role in attention, perception, awareness, thought, memory, language, and consciousness. The cerebral cortex is part of the brain responsible for cognition.
The thalamus is a large mass of gray matter located in the dorsal part of the diencephalon. Nerve fibers project out of the thalamus to the cerebral cortex in all directions, allowing hub-like exchanges of information. It has several functions, such as the relaying of sensory signals, including motor signals to the cerebral cortex and the regulation of consciousness, sleep, and alertness.
The development of the nervous system, or neural development (neurodevelopment), refers to the processes that generate, shape, and reshape the nervous system of animals, from the earliest stages of embryonic development to adulthood. The field of neural development draws on both neuroscience and developmental biology to describe and provide insight into the cellular and molecular mechanisms by which complex nervous systems develop, from nematodes and fruit flies to mammals.
Sonic hedgehog protein(SHH) is encoded for by the SHH gene. The protein is named after the character Sonic the Hedgehog.
Glia, also called glial cells(gliocytes) or neuroglia, are non-neuronal cells in the central nervous system (brain and spinal cord) and the peripheral nervous system that do not produce electrical impulses. The neuroglia make up more than one half the volume of neural tissue in our body. They maintain homeostasis, form myelin in the peripheral nervous system, and provide support and protection for neurons. In the central nervous system, glial cells include oligodendrocytes, astrocytes, ependymal cells and microglia, and in the peripheral nervous system they include Schwann cells and satellite cells.
Neurulation refers to the folding process in vertebrate embryos, which includes the transformation of the neural plate into the neural tube. The embryo at this stage is termed the neurula.
In the vertebrate embryo, a rhombomere is a transiently divided segment of the developing neural tube, within the hindbrain region in the area that will eventually become the rhombencephalon. The rhombomeres appear as a series of slightly constricted swellings in the neural tube, caudal to the cephalic flexure. In human embryonic development, the rhombomeres are present by day 29.
Noggin, also known as NOG, is a protein that is involved in the development of many body tissues, including nerve tissue, muscles, and bones. In humans, noggin is encoded by the NOG gene. The amino acid sequence of human noggin is highly homologous to that of rat, mouse, and Xenopus.
The zona limitans intrathalamica (ZLI) is a lineage-restriction compartment and primary developmental boundary in the vertebrate forebrain that serves as a signaling center and a restrictive border between the thalamus and the prethalamus.
Müller glia, or Müller cells, are a type of retinal glial cells, first recognized and described by Heinrich Müller. They are found in the vertebrate retina, where they serve as support cells for the neurons, as all glial cells do. They are the most common type of glial cell found in the retina. While their cell bodies are located in the inner nuclear layer of the retina, they span across the entire retina.
The development of the nervous system in humans, or neural development or neurodevelopment involves the studies of embryology, developmental biology, and neuroscience to describe the cellular and molecular mechanisms by which the complex nervous system forms in humans, develops during prenatal development, and continues to develop postnatally.
Homeobox protein GBX-2 is a protein that in humans is encoded by the GBX2 gene.
The Protomap is a primordial molecular map of the functional areas of the mammalian cerebral cortex during early embryonic development, at a stage when neural stem cells are still the dominant cell type. The protomap is a feature of the ventricular zone, which contains the principal cortical progenitor cells, known as radial glial cells. Through a process called 'cortical patterning', the protomap is patterned by a system of signaling centers in the embryo, which provide positional information and cell fate instructions. These early genetic instructions set in motion a development and maturation process that gives rise to the mature functional areas of the cortex, for example the visual, somatosensory, and motor areas. The term protomap was coined by Pasko Rakic. The protomap hypothesis was opposed by the protocortex hypothesis, which proposes that cortical proto-areas initially have the same potential, and that regionalization in large part is controlled by external influences, such as axonal inputs from the thalamus to the cortex. However, a series of papers in the year 2000 and in 2001 provided strong evidence against the protocortex hypothesis, and the protomap hypothesis has been well accepted since then. The protomap hypothesis, together with the related radial unit hypothesis, forms our core understanding of the embryonic development of the cerebral cortex. Once the basic structure is present and cortical neurons have migrated to their final destinations, many other processes contribute to the maturation of functional cortical circuits.
The rhombic lip is a posterior section of the developing metencephalon which can be recognized transiently within the vertebrate embryo. It extends posteriorly from the roof of the fourth ventricle to dorsal neuroepithelial cells. The rhombic lip can be divided into eight structural units based on rhombomeres 1-8 (r1-r8), which can be recognized at early stages of hindbrain development. Producing granule cells and five brainstem nuclei, the rhombic lip plays an important role in developing a complex cerebellar neural system.
A cerebral organoid, or brain organoid, describes an artificially grown, in vitro, miniature organ resembling the brain. Cerebral organoids are created by culturing pluripotent stem cells in a three-dimensional rotational bioreactor, and they develop over a course of months. The brain is an extremely complex system of heterogeneous tissues and consists of a diverse array of neurons. This complexity has made studying the brain and understanding how it works a difficult task in neuroscience, especially when it comes to neurodegenerative diseases. The purpose of creating an in vitro neurological model is to study these diseases in a more simple and variable space. This 3D model is free of many potential in vivo limitations. The varying physiology between human and other mammalian models limits the scope of study in neurological disorders. Cerebral organoids are synthesized tissues that contain several types of nerve cells and have anatomical features that recapitulate regions of the cortex observed in brains. Cerebral organoids are most similar to layers of neurons called the cortex and choroid plexus. In some cases, structures similar to the retina, meninges and hippocampus can form. Stem cells have the potential to grow into many different types of tissues, and their fate is dependent on many factors. Below is an image showing some of the chemical factors that can lead stem cells to differentiate into various neural tissues; a more in-depth table of generating specific organoid identity has been published since. Similar techniques are used on stem cells used to grow cerebral organoids.
Segmentation is the physical characteristic by which the human body is divided into repeating subunits called segments arranged along a longitudinal axis. In humans, the segmentation characteristic observed in the nervous system is of biological and evolutionary significance. Segmentation is a crucial developmental process involved in the patterning and segregation of groups of cells with different features, generating regional properties for such cell groups and organizing them both within the tissues as well as along the embryonic axis.
Neurogenesis is the process by which nervous system cells, the neurons, are produced by neural stem cells (NSCs). In short, it is brain growth in relation to its organization. This occurs in all species of animals except the porifera (sponges) and placozoans. Types of NSCs include neuroepithelial cells (NECs), radial glial cells (RGCs), basal progenitors (BPs), intermediate neuronal precursors (INPs), subventricular zone astrocytes, and subgranular zone radial astrocytes, among others.
Robb Krumlauf is an American developmental biologist. He is best known for researching the Hox family of transcription factors. He is most interested in understanding the role of the Hox genes in the hindbrain and their role in areas of animal development, such as craniofacial development. Krumlauf worked with a variety of renowned scientists in the field of developmental biology throughout his time researching Hox genes.
François Guillemot,, is a French neurobiologist, currently working at the Francis Crick Institute in London. His research focuses on the behaviour of neural stem cells in embryos and adult brains.
