Craniofacial Muscles

Chapter 4
Motor Control of Extraocular Muscle
Vallabh E. Das
4.1 Introduction
Six pairs of extraocular muscles (EOMs) are innervated by three pairs of cranial
nerves whose cell bodies lie in three cranial nerve nuclei on each side of the brain,
namely the oculomotor, trochlear, and abducens nuclei. Early studies of the oculomotor
system examined neuronal responses of extraocular motoneurons within
these motor nuclei and developed a framework for understanding the motor control
of EOM (Fuchs and Luschei 1970 ; Keller and Robinson 1971 ) . Perhaps one of the
most signi fi cant and elegant outcomes of some of these studies was the proposal for
a “ fi nal common pathway” for eye movements (Robinson 1968, 1981 ) . Thus,
according to the oculomotor fi nal common pathway theory, motoneuron innervation
of EOM was independent of the type of eye movement that was being executed.
While this framework still has validity in understanding the neural control of eye
movements, there have been new developments in the last couple of decades that
has brought about renewed interest in the oculomotor periphery and cast doubt on
the so-called “ fi nal common pathway.” The goals of this chapter are to review ocular
biomechanics and motor control of EOM while highlighting new developments and
identifying issues that are yet unresolved. We have con fi ned our discussion to the
motor neurons and their effector organ, the eye. Central control of eye movements
is outside the scope of this chapter.
V. E. Das , Ph.D. (*)
College of Optometry , University of Houston , Houston , TX 77204, USA
e-mail: vdas@optometry.uh.edu
L.K. McLoon and F.H. Andrade (eds.), Craniofacial Muscles: A New Framework
for Understanding the Effector Side of Craniofacial Muscle Control,
DOI 10.1007/978-1-4614-4466-4_4, © Springer Science+Business Media New York 2013
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