fasciculus
(fă-sik'yŭ-lŭs 
, fă-sik'yŭ-lī‵)
Plural: fasciculi
[L. fasciculus, a small bundle]
- A small bundle of longitudinal elements, e.g., muscle fibers.
- A bundle of axons. Peripheral nerves can contain one or more axonal fasciculi. In the brain and spinal cord, many of the fasciculi are named, and fasciculus and tract are synonymous.
arcuate f.A myelinated association tract connecting the superior and middle gyri of the frontal lobe with the ipsilateral temporal lobe.
f. cuneatus The more lateral of the two large ascending axon tracts that fill the dorsal funiculus of the spinal cord. The fasciculus cuneatus contains spinal ganglion cell axons transmitting fine touch, conscious proprioception and vibratory sense from the ipsilateral arm, shoulder, and neck. SYN: root zone.
dorsal longitudinal f.An axon tract that interconnects the brainstem reticular formation and the hypothalamus.
dorsolateral f.Lissauer tract.
fronto-occipital f.A myelinated axon tract lying under the cerebral cortex. It is a long association tract that interconnects the frontal lobe with the ipsilateral temporal and occipital lobes.
fundamental f.The portion of the anterior column of the spinal cord continuing into the medulla oblongata.
f. gracilis The more medial of the two large ascending axon tracts that fill the posterior funiculus of the spinal cord. This fasciculus contains spinal ganglion cell axons transmitting fine touch, conscious proprioception, and vibratory sense from the legs and trunk.
inferior longitudinal f.A myelinated axon tract lying under the cerebral cortex. It is a long association tract interconnecting the occipital lobe with the ipsilateral temporal lobe.
ABBR: MLF
A long, discrete axon tract running ventrally, close to the midline, through the brainstem and upper spinal cord. With contributions from the vestibulospinal tracts, the medial longitudinal fasciculus is the main pathway by which equilibrium and balance information reaches lower motor neuron circuits to automatically adjust eye, neck, and limb movements to match sensory signals from the semicircular canals. SYN: medial longitudinal bundle.posterior longitudinal f.An axon tract running between the corpora quadrigemina and the nuclei of the fourth and sixth spinal nerves.
posterolateral f.Lissauer tract.
f. retroflexus The main output tract from the habenular nuclei, which lie above the thalamus. It innervates the interpeduncular nuclei, which then send axons to the median raphe nuclei of the midbrain SYN: habenulo-interpeduncular tract.
f. solitarius Tractus solitarius.
sublenticular f.Acoustic radiation
superior longitudinal f.A myelinated axon tract lying under the cerebral cortex. It is a long association tract that interconnects the superior and middle gyri of the frontal lobe with the ipsilateral parietal and occipital lobes.
thalamic f.A heterogeneous bundle of axons heading dorsally into the ventral anterior and ventral lateral thalamic nuclei. Axons in this fasciculus include part of the ansa lenticularis (from the globus pallidus) and axons from the contralateral deep cerebellar nuclei.
uncinate f.A compact, myelinated axon tract lying under the cerebral cortex. It is a long association tract that interconnects the frontal association cortex of the frontal lobe with the inferior temporal association cortex of the ipsilateral temporal lobe.