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.
Neuroanatomy is the study of the structure and organization of the nervous system. In contrast to animals with radial symmetry, whose nervous system consists of a distributed network of cells, animals with bilateral symmetry have segregated, defined nervous systems. Their neuroanatomy is therefore better understood. In vertebrates, the nervous system is segregated into the internal structure of the brain and spinal cord and the series of nerves that connect the CNS to the rest of the body. Breaking down and identifying specific parts of the nervous system has been crucial for figuring out how it operates. For example, much of what neuroscientists have learned comes from observing how damage or "lesions" to specific brain areas affects behavior or other neural functions.
A histochemical tracer is a compound used to reveal the location of cells and track neuronal projections. A neuronal tracer may be retrograde, anterograde, or work in both directions. A retrograde tracer is taken up in the terminal of the neuron and transported to the cell body, whereas an anterograde tracer moves away from the cell body of the neuron.
Behavioral neuroscience, also known as biological psychology, biopsychology, or psychobiology, is the application of the principles of biology to the study of physiological, genetic, and developmental mechanisms of behavior in humans and other animals.
Immediate early genes (IEGs) are genes which are activated transiently and rapidly in response to a wide variety of cellular stimuli. They represent a standing response mechanism that is activated at the transcription level in the first round of response to stimuli, before any new proteins are synthesized. IEGs are distinct from "late response" genes, which can only be activated later, following the synthesis of early response gene products. Thus IEGs have been called the "gateway to the genomic response". The term can describe viral regulatory proteins that are synthesized following viral infection of a host cell, or cellular proteins that are made immediately following stimulation of a resting cell by extracellular signals.
A neural circuit is a population of neurons interconnected by synapses to carry out a specific function when activated. Multiple neural circuits interconnect with one another to form large scale brain networks.
Hydroxystilbamidine is a fluorescent dye that emits different frequencies of light when bound to DNA and RNA. It is used as a retrograde tracer for outlining neurons, and as a histochemical stain.
Axonal transport, also called axoplasmic transport or axoplasmic flow, is a cellular process responsible for movement of mitochondria, lipids, synaptic vesicles, proteins, and other organelles to and from a neuron's cell body, through the cytoplasm of its axon called the axoplasm. Since some axons are on the order of meters long, neurons cannot rely on diffusion to carry products of the nucleus and organelles to the ends of their axons. Axonal transport is also responsible for moving molecules destined for degradation from the axon back to the cell body, where they are broken down by lysosomes.
Aujeszky's disease, usually called pseudorabies in the United States, is a viral disease in swine that is endemic in most parts of the world. It is caused by Suid herpesvirus 1 (SuHV-1). Aujeszky's disease is considered to be the most economically important viral disease of swine in areas where classical swine fever has been eradicated. Other mammals, such as cattle, sheep, goats, cats, dogs, and raccoons, are also susceptible. The disease is usually fatal in these animal species.
Neuromorphology is the study of nervous system form, shape, and structure. The study involves looking at a particular part of the nervous system from a molecular and cellular level and connecting it to a physiological and anatomical point of view. The field also explores the communications and interactions within and between each specialized section of the nervous system. Morphology is distinct from morphogenesis. Morphology is the study of the shape and structure of biological organisms, while morphogenesis is the study of the biological development of the shape and structure of organisms. Therefore, neuromorphology focuses on the specifics of the structure of the nervous system and not the process by which the structure was developed. Neuromorphology and morphogenesis, while two different entities, are nonetheless closely linked.
Brainbow is a process by which individual neurons in the brain can be distinguished from neighboring neurons using fluorescent proteins. By randomly expressing different ratios of red, green, and blue derivatives of green fluorescent protein in individual neurons, it is possible to flag each neuron with a distinctive color. This process has been a major contribution to the field of neural connectomics.
In neuroscience, anterograde tracing is a research method that is used to trace axonal projections from their source to their point of termination. A hallmark of anterograde tracing is the labeling of the presynaptic and the postsynaptic neuron(s). The crossing of the synaptic cleft is a vital difference between the anterograde tracers and the dye fillers used for morphological reconstruction. The complementary technique is retrograde tracing, which is used to trace neural connections from their termination to their source. Both the anterograde and retrograde tracing techniques are based on the visualization of the biological process of axonal transport.
Developmental plasticity is a general term referring to changes in neural connections during development as a result of environmental interactions as well as neural changes induced by learning. Much like neuroplasticity, or brain plasticity, developmental plasticity is specific to the change in neurons and synaptic connections as a consequence of developmental processes. A child creates most of these connections from birth to early childhood. There are three primary methods by which this may occur as the brain develops, but critical periods determine when lasting changes may form. Developmental plasticity may also be used in place of the term phenotypic plasticity when an organism in an embryonic or larval stage can alter its phenotype based on environmental factors. However, a main difference between the two is that phenotypic plasticity experienced during adulthood can be reversible, whereas traits that are considered developmentally plastic set foundations during early development that remain throughout the life of the organism.
Neurovirology is an interdisciplinary field which represents a melding of clinical neuroscience, virology, immunology, and molecular biology. The main focus of the field is to study viruses capable of infecting the nervous system. In addition to this, the field studies the use of viruses to trace neuroanatomical pathways, for gene therapy, and to eliminate detrimental populations of neural cells.
Biotinylated dextran amines (BDA) are organic compounds used as anterograde and retrograde neuroanatomical tracers. They can be used for labeling the source as well as the point of termination of neural connections and therefore to study neural pathways.
GCaMP is a genetically encoded calcium indicator (GECI) initially developed in 2001 by Junichi Nakai. It is a synthetic fusion of green fluorescent protein (GFP), calmodulin (CaM), and M13, a peptide sequence from myosin light-chain kinase. When bound to Ca2+, GCaMP fluoresces green with a peak excitation wavelength of 480 nm and a peak emission wavelength of 510 nm. It is used in biological research to measure intracellular Ca2+ levels both in vitro and in vivo using virally transfected or transgenic cell and animal lines. The genetic sequence encoding GCaMP can be inserted under the control of promoters exclusive to certain cell types, allowing for cell-type specific expression of GCaMP. Since Ca2+ is a second messenger that contributes to many cellular mechanisms and signaling pathways, GCaMP allows researchers to quantify the activity of Ca2+-based mechanisms and study the role of Ca2+ ions in biological processes of interest.
Viral neuronal tracing is the use of a virus to trace neural pathways, providing a self-replicating tracer. Viruses have the advantage of self-replication over molecular tracers but can also spread too quickly and cause degradation of neural tissue. Viruses that can infect the nervous system, called neurotropic viruses, spread through spatially close assemblies of neurons through synapses, allowing for their use in studying functionally connected neural networks.
Neuronal tracing, or neuron reconstruction is a technique used in neuroscience to determine the pathway of the neurites or neuronal processes, the axons and dendrites, of a neuron. From a sample preparation point of view, it may refer to some of the following as well as other genetic neuron labeling techniques,
Calcium imaging is a microscopy technique to optically measure the calcium (Ca2+) status of an isolated cell, tissue or medium. Calcium imaging takes advantage of calcium indicators, fluorescent molecules that respond to the binding of Ca2+ ions by fluorescence properties. Two main classes of calcium indicators exist: chemical indicators and genetically encoded calcium indicators (GECI). This technique has allowed studies of calcium signalling in a wide variety of cell types. In neurons, action potential generation is always accompanied by rapid influx of Ca2+ ions. Thus, calcium imaging can be used to monitor the electrical activity in hundreds of neurons in cell culture or in living animals, which has made it possible to observe the activity of neuronal circuits during ongoing behavior.
Fiber photometry is a calcium imaging technique that captures 'bulk' or population-level calcium (Ca2+) activity from specific cell-types within a brain region or functional network in order to study neural circuits Population-level calcium activity can be correlated with behavioral tasks, such as spatial learning, memory recall and goal-directed behaviors. The technique involves the surgical implantation of fiber optics into the brains of living animals. The benefits to researchers are that optical fibers are simpler to implant, less invasive and less expensive than other calcium methods, and there is less weight and stress on the animal, as compared to miniscopes. It also allows for imaging of multiple interacting brain regions and integration with other neuroscience techniques. The limitations of fiber photometry are low cellular and spatial resolution, and the fact that animals must be securely tethered to a rigid fiber bundle, which may impact the naturalistic behavior of smaller mammals such as mice.
