Semicircular canal geometry, afferent sensitivity, and animal behavior

The geometry of the semicircular canals has been used in evolutionary studies to predict the behaviors of extinct animals. These predictions have relied on an assumption that the responses of the canals can be determined from their dimensions, and that an organism's behavior can be determined f...

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Bibliographic Details
Published in:The anatomical record. Part A, Discoveries in molecular, cellular, and evolutionary biology Discoveries in molecular, cellular, and evolutionary biology, 2006-04, Vol.288A (4), p.466-472
Main Author: Hullar, Timothy E.
Format: Article
Language:English
Subjects:
Animals
Behavior, Animal
Cats
Columbidae
evolution
labyrinth
Neurons, Afferent - physiology
Saimiri
Semicircular Canals - anatomy & histology
Semicircular Canals - innervation
torsion‐pendulum
vestibular
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Summary:The geometry of the semicircular canals has been used in evolutionary studies to predict the behaviors of extinct animals. These predictions have relied on an assumption that the responses of the canals can be determined from their dimensions, and that an organism's behavior can be determined from these responses. However, the relationship between a canal's sensitivity and its size is not well known. An intraspecies comparison among canal responses in each of three species (cat, squirrel monkey, and pigeon) was undertaken to evaluate various models of canal function and determine how their dimensions may be related to afferent physiology. All models predicted the responses of the cat afferents, but the models performed less well for squirrel monkey and pigeon. Possible causes for this discrepancy include incorrectly assuming that afferent responses accurately represent canal function or errors in current biophysical models of the canals. These findings leave open the question as to how reliably canal anatomy can be used to estimate afferent responses and how closely afferent responses are related to behavior. Other labyrinthine features, such as orientation of the horizontal canal, which is reliably held near earth‐horizontal across many species, may be better to use when extrapolating the posture and related behavior of extinct animals from labyrinthine morphology. Anat Rec Part A, 2006. © 2006 Wiley‐Liss, Inc.
ISSN:1552-4884
1552-4892
DOI:10.1002/ar.a.20304