Association fibers are
axon
An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, spelling differences) is a long, slender cellular extensions, projection of a nerve cell, or neuron, ...
s (nerve fibers) that connect
cortical areas within the same
cerebral hemisphere
The vertebrate cerebrum (brain) is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres ...
.
In human neuroanatomy, axons within the brain, can be categorized on the basis of their course and connections as association fibers,
projection fibers, and
commissural fibers
The commissural fibers or transverse fibers are axons that connect the two hemispheres of the brain. Huge numbers of commissural fibers make up the commissural tracts in the brain, the largest of which is the corpus callosum.
In contrast to ...
.
Bundles of fibers are known as
nerve tract
A nerve tract is a bundle of nerve fibers (axons) connecting Nucleus (neuroanatomy), nuclei of the central nervous system. In the peripheral nervous system, this is known as a nerve fascicle, and has associated nervous tissue, connective tissue. T ...
s, and consist of
association tracts,
commissural tracts, and
projection tracts.
The association fibers unite different parts of the same
cerebral hemisphere
The vertebrate cerebrum (brain) is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres ...
, and are of two kinds: (1) short association fibers that connect adjacent gyri; (2) long association fibers that make connections between more distant parts.
Short association fibers
Many of the short association fibers (also called arcuate or "U"-fibers) lie in the superficial white matter immediately beneath the gray matter of the cerebral cortex, and connect together adjacent
gyri
In neuroanatomy, a gyrus (: gyri) is a ridge on the cerebral cortex. It is generally surrounded by one or more sulcus (neuroanatomy), sulci (depressions or furrows; : sulcus). Gyri and sulci create the folded appearance of the brain in huma ...
.
Some pass from one wall of the sulcus to the other.
Long association fibers
The long association fibers connect the more widely separated gyri and are grouped into bundles.
They include the following:
Diffusion tensor imaging is a non-invasive method to study the course of association fibers.
See also
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Interneuron
Interneurons (also called internuncial neurons, association neurons, connector neurons, or intermediate neurons) are neurons that are not specifically motor neurons or sensory neurons. Interneurons are the central nodes of neural circuits, enab ...
*
Tractography
References
External links
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Cerebral white matter