Axonets

Axonets are networks of axons that connect neurons across different brain regions, forming the white matter architecture that underpins fast and coordinated neural communication. The term is used in neuroscience to describe the interconnected pathways by which electrical signals travel, enabling integration of information across distant parts of the nervous system. Axonets include commissural tracts that cross between hemispheres, such as the corpus callosum; association tracts that connect regions within the same hemisphere, such as the superior longitudinal fasciculus; and projection tracts that carry signals to and from the brainstem and spinal cord, including the corticospinal tract.

Structurally, axonets consist of bundles of axons that may be myelinated or unmyelinated, organized into fascicles and fiber bundles. Myelination by oligodendrocytes increases conduction velocity and supports rapid synchronization of activity among neural populations. During development, axonets are shaped by axonal guidance cues and later refined through myelination and activity-dependent plasticity, contributing to the maturation of cognitive and motor functions.

Methods for studying axonets include diffusion MRI and tractography, which infer the presence and orientation of white matter pathways, complemented by histological techniques in animal and human tissue. These approaches have advanced mapping of large-scale connectivity but face limitations in resolving crossing fibers and determining directionality.

Clinically, changes in axonets are associated with a range of conditions such as traumatic brain injury, demyelinating diseases, and neurodevelopmental disorders. Quantitative assessments of white matter integrity and tract connectivity can aid in diagnosis, prognosis, and monitoring of treatment effects.

See also: white matter, diffusion tensor imaging, tractography, axonal tract, neural connectivity.