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This allows researchers to quantify anatomical features of the brain in terms of shape, mass, volume (e.g. of the hippocampus, or of the primary versus secondary visual cortex), and to derive more specific information, such as the encephalization quotient, grey matter density and white matter connectivity, gyrification, cortical thickness, or ...
White matter is the tissue through which messages pass between different areas of grey matter within the central nervous system. The white matter is white because of the fatty substance (myelin) that surrounds the nerve fibers (axons). This myelin is found in almost all long nerve fibers, and acts as an electrical insulation.
The cerebral blood volume value of gray matter is about 3.5 +/- 0.4 ml/100g, and the white matter is about 1.7 +/- 0.4 ml/100g. The gray matter is nearly twice that of white matter. [3] In both white and gray matter, cerebral blood volume decreases by about 0.50% per year with increasing age. [4]
This shape is often modeled as an ellipsoid, and the technique is then called diffusion tensor imaging. [4] Barriers can be many things: cell membranes, axons, myelin, etc.; but in white matter the principal barrier is the myelin sheath of axons. Bundles of axons provide a barrier to perpendicular diffusion and a path for parallel diffusion ...
The topographical relationships between independent measures of white matter and gray matter integrity suggest that rich developmental or environmental interactions influence brain structure and function. The presence and strength of such associations may elucidate pathophysiological processes influencing systems such as language and motor planning
The external capsule is a series of white matter fiber tracts in the brain. These fibers run between the most lateral (toward the side of the head) segment of the lentiform nucleus (more specifically the putamen) and the claustrum. The white matter of the external capsule contains fibers known as corticocortical association fibers.
For example, deep white matter hyperintensities are 2.5 to 3 times more likely to occur in bipolar disorder and major depressive disorder than control subjects. [3] [4] WMH volume, calculated as a potential diagnostic measure, has been shown to correlate to certain cognitive factors. [5]
The substantia innominata, also innominate substance or substantia innominata of Meynert (Latin for unnamed substance), is a series of layers in the human brain consisting partly of gray and partly of white matter, which lies below the anterior part of the thalamus and lentiform nucleus.