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Brain Behav Evol 2014;83:162-175
(DOI:10.1159/000357833)

Connecting Ears to Eye Muscles: Evolution of a ‘Simple' Reflex Arc

Straka H.a · Fritzsch B.b · Glover J.C.c

Author affiliations

aDepartment of Biology II, Ludwig Maximilians University Munich, Planegg, Germany; bDepartment of Biology, University of Iowa, Iowa City, Iowa, USA; cDepartment of Physiology, University of Oslo, Oslo, Norway

Corresponding Author

Dr. Joel C. Glover

Department of Physiology, Institute of Basic Medical Sciences

University of Oslo

PB 1103 Blindern, NO-0317 Oslo (Norway)

E-Mail joel.glover@medisin.uio.no

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Abstract

Developmental and evolutionary data from vertebrates are beginning to elucidate the origin of the sensorimotor pathway that links gravity and motion detection to image-stabilizing eye movements - the vestibulo-ocular reflex (VOR). Conserved transcription factors coordinate the development of the vertebrate ear into three functional sensory compartments (graviception/translational linear acceleration, angular acceleration and sound perception). These sensory components connect to specific populations of vestibular and auditory projection neurons in the dorsal hindbrain through undetermined molecular mechanisms. In contrast, a molecular basis for the patterning of the vestibular projection neurons is beginning to emerge. These are organized through the actions of rostrocaudally and dorsoventrally restricted transcription factors into a ‘hodological mosaic' within which coherent and largely segregated subgroups are specified to project to different targets in the spinal cord and brain stem. A specific set of these regionally diverse vestibular projection neurons functions as the central element that transforms vestibular sensory signals generated by active and passive head and body movements into motor output through the extraocular muscles. The large dynamic range of motion-related sensory signals requires an organization of VOR pathways as parallel, frequency-tuned, hierarchical connections from the sensory periphery to the motor output. We suggest that eyes, ears and functional connections subserving the VOR are vertebrate novelties that evolved into a functionally coherent motor control system in an almost stereotypic organization across vertebrate taxa.

© 2014 S. Karger AG, Basel


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Article / Publication Details

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Abstract of  

Received: December 03, 2013
Accepted: December 05, 2013
Published online: April 24, 2014

Number of Print Pages: 14
Number of Figures: 4
Number of Tables: 0

ISSN: 0006-8977 (Print)
eISSN: 1421-9743 (Online)

For additional information: https://www.karger.com/BBE