Speed limits in the cerebellum: constraints from myelinated and unmyelinated parallel fibers.
Eur J Neurosci
; 21(8): 2285-90, 2005 Apr.
Article
en En
| MEDLINE
| ID: mdl-15869526
ABSTRACT
Cerebellar parallel fibers are among the thinnest known vertebrate axons and represent an extreme anatomical adaptation. Until now a systematic examination of their properties across species has not been carried out. We used transmission electron microscopy and light microscopy to compare parallel fibers in mammals of different brain sizes. From mouse to macaque, the average unmyelinated parallel fiber diameter was 0.2-0.3 microm, consistent with the idea that they are evolutionarily selected for compactness. Average unmyelinated parallel fiber diameter scaled up slightly with brain size, and across species the estimated total conduction time is 5-10 ms. However, these conduction times can vary by milliseconds, and unmyelinated PFs consume large amounts of energy per action potential. These functional disadvantages are overcome in myelinated parallel fibers, which we found in the deep regions nearest the Purkinje cell layer in marmoset, cat and macaque. These axons were 0.4-1.1 microm wide, have expected conduction times of 0.5-1.0 ms, and may convey fast feedforward inhibition via basket cells to Purkinje cells.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Cerebelo
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Fibras Nerviosas Amielínicas
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Fibras Nerviosas Mielínicas
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Conducción Nerviosa
Límite:
Animals
Idioma:
En
Revista:
Eur J Neurosci
Asunto de la revista:
NEUROLOGIA
Año:
2005
Tipo del documento:
Article
País de afiliación:
Estados Unidos