Consequences of Excessive Chronic Alcohol Consumption on Brain Structure and Function
John Brick in Handbook of the Medical Consequences of Alcohol and Drug Abuse, 2012
Conventional structural MRI takes advantage of the water-based composition of the brain comprising gray matter (about 80 percent water), white matter (about 70 percent water), and cerebrospinal fluid (CSF) (100 percent water) to reveal the size, shape, and tissue composition (gray versus white matter) of the brain and its constituent parts. Gray matter consists of neurons and surrounding glial cells. White matter is made up of long, thin, nerve cell fibers called axons that carry information between neurons. White matter is paler in color than gray matter because the axons are surrounded by myelin, which is a system of cell bodies (oligodendrocytes) that wind around the axon and augment neural transmission. The axons form fiber tracts linking near and distant neurons across different brain regions (i.e., white matter tracts). Structural MRI enables the identification of differences in brain tissue types and structures by manipulating the way in which water protons are excited, yielding intensity differences between tissue types that enable gross brain neuroanatomy (macrostructure) to be mapped. Typically these structural images are segmented to differentiate gray matter, white matter, and CSF the liquid that fills inner spaces and surrounds the brain within the skull. Volumes of gray matter, white matter, and CSF can then be measured in different regions of the brain. In addition, specific neuroanatomic structures such as the corpus callosum, hippocampus, and basal ganglia can be outlined and their volumes measured.
Disruptions in physical substrates of vision following traumatic brain injury
Mark J. Ashley, David A. Hovda in Traumatic Brain Injury, 2017
The brain has two solid components and four anatomical parts. The two core components are the gray matter and the white matter. Gray matter can be likened to a series of computers with the white matter being the wiring connecting them to one another. The major component of the gray matter includes neuronal cell bodies, called neurons. They have cellular extensions called dendrites and axons (the latter both myelinated and unmyelinated). Neurons are electrically polarized cells that specialize for conductance of electrical impulses projected down the axons and transmitted chemically over spaces called synapses to the dendrites of the next neuron. Electrical connectivity of large groups of neurons is termed brain circuitry. Besides intercellular connectivity, there is also intracellular connectivity, referred to as transduction. This total transfer of information is called cell signaling.
Comparison of 3D visualization results of segmented white and gray matter from T1 and T2 – weighted MRI data
Waldemar Wójcik, Sergii Pavlov, Maksat Kalimoldayev in Information Technology in Medical Diagnostics II, 2019
Due to the fact that the brain is the most complicated structure in the human body, it creates problems with a accurate analysis of its image. The segmentation process usually focuses on the most important elements and tissues such as gray matter, white matter, spinal fluid or skull bones. White matter is one of the two basic components of the central nervous system. These are well-vascularized clusters of neurons (dendrites and axons), whose bodies are found in the gray matter. This tissue is situated beneath the cerebral cortex and forms various pathways connecting individual areas of the cortex and post-articular areas. The inverse position of the white matter occurs in the medulla and spinal cord. There, it is located around a centrally located gray matter, which is the second component of the central nervous system. In the encephalon, the gray matter is located on the surface of the brain and cerebellum forming the cortex (Wolak 2010, Ramaiah & Mohan 2011).
Marijuana matters: reviewing the impact of marijuana on cognition, brain structure and function, & exploring policy implications and barriers to research
Published in International Review of Psychiatry, 2018
Kelly A. Sagar, Staci A. Gruber
Brain imaging techniques have also afforded researchers the opportunity to examine the impact of MJ use on brain structure, including measures of both grey and white matter. Grey matter consists of neuronal cell bodies and is responsible for information processing and decision-making. White matter is comprised of nerve axons, controls the signals that neurons share, and is critical for coordinating efficient communication between brain regions. Reviews documenting the structural impact of MJ use often report bidirectional findings, which are typically related to the brain region under examination (Batalla et al., 2013). Interestingly, however, alterations are most often observed in areas with high densities of CB1 receptors (Lorenzetti et al., 2016), and may also be influenced by age of onset and increased MJ use (Filbey, McQueeny, DeWitt, & Mishra, 2015). In a recent review, Lorenzetti et al. (2016) found that while larger cerebellar and striatal volumes have been observed in MJ users, regular MJ users often exhibit reductions in grey matter volume in several other regions, particularly the hippocampus. Importantly, studies have found that structural alterations in a number of brain regions appear to be related to increased executive dysfunction (Churchwell, Lopez-Larson, & Yurgelun-Todd, 2010; Medina et al., 2009; Medina, Nagel, & Tapert, 2010; Price et al., 2015) and poorer verbal memory (Ashtari et al., 2011).
Effect of axonal fiber architecture on mechanical heterogeneity of the white matter—a statistical micromechanical model
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Hesam Hoursan, Farzam Farahmand, Mohammad Taghi Ahmadian
Human brain white matter consists of axonal bundles which connect nerve cell bodies mostly located in the grey matter. A sudden inertial loading on the head can cause Diffuse Axonal Injury (DAI) of white matter, which involves axonal damage in a variety of modes. Among the failure modes of axons, rapid stretching of neural tracts, leading to the impairment of axoplasmic transport and subsequent swelling and neuropathologic problems, has been reported to be the prevailing failure mode (McKenzie et al. 1996; Smith and Meaney 2000; Di Pietro 2013). DAI tends to occur in three anatomical regions of white matter, known as the “injury triad”: the lobar white matter (including corona radiata), the corpus callosum, and the dorsolateral quadrant of the rostal brainstem, adjacent to the superior cerebellar peduncle (Tsao 2012).
Tailoring synthetic polymeric biomaterials towards nerve tissue engineering: a review
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2019
Hamed Amani, Hanif Kazerooni, Hossein Hassanpoor, Abolfazl Akbarzadeh, Hamidreza Pazoki-Toroudi
The spinal cord structure is simpler relative to the brain but it is more vulnerable in trauma [28]. Although the spinal cord is protected by several structures including cerebrospinal fluid, three meningeal layers, and vertebrae relative to extending peripheral nerves, a growing list and high incidence of SCI cases have been reported around the world in recent years (between 12,000–15,000 people in North America each year) [29]. Generally, the spinal cord is formed from grey matter (butterfly-shaped area) that is surrounded by white matter. The grey matter includes lower motor neurons (a receipt of signals from upper motor neurons in the brain), sensory neurons (a receipt of signals from the periphery), glial cells and blood vessels. The axons and glial cells such as astrocytes, oligodendrocytes, and microglia are the main components of the white matter in the spinal cord.