272
remains unclear how these organs simultaneously integrate bimodal sensory input
such as sound and self-generated movement.
Fish also possess a hair cell based mechanosensory lateral line which functions
in schooling behavior (Partridge and Pitcher 1980 ), rheotaxis (Montgomery et al.
1997 ), localization of underwater objects (Weissert and von Campenhausen 1981 ),
and predator/prey interactions (Montgomery et al. 1995 ). Unlike the inner ear, the
lateral line was not retained throughout vertebrate evolution and is limited to fi sh
and aquatic amphibians. Although the role of the lateral line in sound detection has
long been debated (see Braun et al. 2002 for review), several studies have suggested
that the fi sh’s mechanosensory lateral line may play a role in sound localization
(Higgs and Radford 2013 ; Mirjany and Faber 2011 ; Mirjany et al. 2011 ; Radford
and Mensinger 2014 ; Weeg and Bass 2002 ). Thus, similar to the otoliths, the mechanosensory lateral line receives multimodal (i.e., vibration and sound) input.
A long-standing question in neuroethology is how fi sh localize sound underwater. Although the saccule is considered the primary auditory endorgan in fi sh (Popper
and Fay 1993 , 2011 ), both the saccule and utricle are sensitive to linear acceleration
and acoustic particle motion, and display directional sensitivity, functioning predominantly as low frequency (60–1000 Hz) detectors (Boyle et al. 2001 ; Fay 1984 ;
Fay and Edds-Walton 2000 ; Lu et al. 2004 ; Mensinger 2006 ). However, the mechanism by which otoliths contribute to sound localization remains unclear. While terrestrial vertebrates use interaural time delays to localize sound in the azimuth
(Schnupp and Carr 2009 ), the small distances between otolith pairs, the low density
of the cerebral spinal fl uid and/or brain tissue in the intervening space and the relatively rapid underwater speed of sound, makes using time disparities challenging for
teleosts. Further complicating matters is the otoliths’ vestibular role as any selfgenerated movement may impact auditory sensitivity.
The traditional neurophysiological method of recording from restrained, anesthetized fi sh complicates investigating bimodal sensory input, especially associated
with self-movement (i.e., respiration, swimming). Semi-submerged preparations
make it diffi cult to deliver and/or quantify the sound impacting the otoliths, while
submerged preparations often are complicated by echoes produced during sound
presentation in small tanks (Mensinger and Deffenbaugh 2000 ). Furthermore, animal care regulations mandate the use of anesthesia with restrained and/or paralyzed
fi sh, which may depress neural sensitivity (Palmer and Mensinger 2004 ). The development of the shaker table by the Fay laboratory (Fay 1984 ) allowed for very accurate measurement of acoustic sensitivity that partially offset previous testing
problems, however it remained limited to restrained fi sh which makes it diffi cult to
test bimodal stimuli.
It has long been the goal of neuroethologists to record from freely moving animals in their natural state. While signifi cant advances have been made with terrestrial animals using radio telemetry for monitoring physiological processes (Kramer
and Kinter 2003 ), the use of these techniques in the aquatic medium has been tempered by its opacity to radio waves and viscosity that produces drag on external
devices. Tethered preparations using swivels have been successful with animals
exhibiting two dimensional movement (i.e., mice in the horizontal plane) (Young
A.F. Mensinger
remains unclear how these organs simultaneously integrate bimodal sensory input
such as sound and self-generated movement.
Fish also possess a hair cell based mechanosensory lateral line which functions
in schooling behavior (Partridge and Pitcher 1980 ), rheotaxis (Montgomery et al.
1997 ), localization of underwater objects (Weissert and von Campenhausen 1981 ),
and predator/prey interactions (Montgomery et al. 1995 ). Unlike the inner ear, the
lateral line was not retained throughout vertebrate evolution and is limited to fi sh
and aquatic amphibians. Although the role of the lateral line in sound detection has
long been debated (see Braun et al. 2002 for review), several studies have suggested
that the fi sh’s mechanosensory lateral line may play a role in sound localization
(Higgs and Radford 2013 ; Mirjany and Faber 2011 ; Mirjany et al. 2011 ; Radford
and Mensinger 2014 ; Weeg and Bass 2002 ). Thus, similar to the otoliths, the mechanosensory lateral line receives multimodal (i.e., vibration and sound) input.
A long-standing question in neuroethology is how fi sh localize sound underwater. Although the saccule is considered the primary auditory endorgan in fi sh (Popper
and Fay 1993 , 2011 ), both the saccule and utricle are sensitive to linear acceleration
and acoustic particle motion, and display directional sensitivity, functioning predominantly as low frequency (60–1000 Hz) detectors (Boyle et al. 2001 ; Fay 1984 ;
Fay and Edds-Walton 2000 ; Lu et al. 2004 ; Mensinger 2006 ). However, the mechanism by which otoliths contribute to sound localization remains unclear. While terrestrial vertebrates use interaural time delays to localize sound in the azimuth
(Schnupp and Carr 2009 ), the small distances between otolith pairs, the low density
of the cerebral spinal fl uid and/or brain tissue in the intervening space and the relatively rapid underwater speed of sound, makes using time disparities challenging for
teleosts. Further complicating matters is the otoliths’ vestibular role as any selfgenerated movement may impact auditory sensitivity.
The traditional neurophysiological method of recording from restrained, anesthetized fi sh complicates investigating bimodal sensory input, especially associated
with self-movement (i.e., respiration, swimming). Semi-submerged preparations
make it diffi cult to deliver and/or quantify the sound impacting the otoliths, while
submerged preparations often are complicated by echoes produced during sound
presentation in small tanks (Mensinger and Deffenbaugh 2000 ). Furthermore, animal care regulations mandate the use of anesthesia with restrained and/or paralyzed
fi sh, which may depress neural sensitivity (Palmer and Mensinger 2004 ). The development of the shaker table by the Fay laboratory (Fay 1984 ) allowed for very accurate measurement of acoustic sensitivity that partially offset previous testing
problems, however it remained limited to restrained fi sh which makes it diffi cult to
test bimodal stimuli.
It has long been the goal of neuroethologists to record from freely moving animals in their natural state. While signifi cant advances have been made with terrestrial animals using radio telemetry for monitoring physiological processes (Kramer
and Kinter 2003 ), the use of these techniques in the aquatic medium has been tempered by its opacity to radio waves and viscosity that produces drag on external
devices. Tethered preparations using swivels have been successful with animals
exhibiting two dimensional movement (i.e., mice in the horizontal plane) (Young
A.F. Mensinger