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The length of cerebellar parallel fibers in chicken and rhesus monkey
Author(s) -
Mugnaini Enrico
Publication year - 1983
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.902200103
Subject(s) - cerebellar cortex , purkinje cell , anatomy , biology , cerebellum , parallel fiber , granular layer , primate , granule cell , climbing fiber , axon , white matter , mossy fiber (hippocampus) , deep cerebellar nuclei , neuroscience , central nervous system , medicine , dentate gyrus , radiology , magnetic resonance imaging
The cerebellar parallel fibers, which course through the molecular layer parallel to the long axes of the cortical folds known as folia, originate from ascending granule cell axons and relay the mossy fiber input to dendrites of Purkinje cells. Purkinje cell axons in the cerebellar white matter collect into sheets or zones oriented at right angles to the folia. Each of these zones, which are approximately 0.5‐1 mm wide, innervates a different portion of the deep cerebellar and the vestibular nuclei. An experimental light microscopic study was carried out to determine the maximal length of parallel fibers in long folia of avian and primate cerebellar cortex. With a fine surgical knife, vermal folia were cut perpendicular to their long axes in four adult White Leghorn hens and in three adult rhesus monkeys deeply anesthetized with sodium pentobarbital. The animals were killed 3‐5 days after the operation. Sections of the transected folia were stained with the Fink‐Heimer or the DeOlmos‐Ir.gram methods, which revealed the anterogradely degenerated parallel fibers as darkly stained dots. In both species, the pattern of parallel fiber regeneration in the molecular layer had a trapezoidal configuration with the shorter base bordering the Purkinje cell layer and the longer base bordering the pia mater. In both species, the length of parallel fibers averaged approximately 6 mm, although the range was 4‐8 mm in chickens and 4.8‐6.6 mm in monkeys. The same trapezoidal pattern of degeneration and average parallel fiber lengths of 6 mm were obtained previously from long folia of cat and rabbit cerebella. Thus, parallel fibers show only small variation in their maximal length in relation to cerebellar size. In all the species studied, parallel fibers are consistently longer than the width of single efferent cortical zones, and they modulate the activity of Purkinje cells projecting to different groups of neurons in the deep nuclei.