202
were included in data sets. The care and use of the toadfish during experimentation
was approved by the IACUC at the MBL and at Loyola University Chicago, Parmly
Hearing Institute.
2.2 Tract-Tracing
The tract-tracing studies included a variety of methods and labels, including DiI
(1,1 dio-octadecyl 3,3,3,3 tetramethyl-indocarbocyanine-perchlorate, Sigma), biotinylated dextran amines (rhodamine, fluoroscein, cascade blue; 3000 and 10,000
MW, Molecular Probes), and neurobiotin (Molecular Probes). Details of the neuranatomical methods may be found in Edds-Walton (1998a, b), Edds-Walton et al.
(1999), and Edds-Walton and Fay (2005a).
2.3 Physiology
All physiological studies were conducted using stimuli produced by the “shaker
system” designed by Fay and described in detail in Fay and Edds-Walton (1997a, b).
This unique stimulus system provides a particle-motion dominated sound field that
is well controlled and predictable. The shaker system consists of a vibrationisolated, open cylinder attached to a single vertical shaker (beneath the cylinder)
and paired mini-shakers (front–back and side–side stimulation). The shaker system
is programmed (and calibrated daily) to provide particle motion stimulation at specified frequencies (50–300 Hz) along designated axes in the horizontal and mid-
sagittal planes (0°, 30°, 60°, 90°, 120°, 150°). Particle motion is a vector quantity
with direction, frequency, and magnitude, and it is the component of sound to which
all fish ears respond (Fay 2005; Popper and Fay 2011; Radford et al. 2012). Simply,
each stimulus (500 ms duration, 20 ms rise, fall; repeated 8 times) consisted of controlled movement along a single axis in a single plane (see Fig. 3 in Edds-Walton
and Fay 2008) to simulate particle motion produced by a sinusoid at a single frequency and designated level (dB re: 1 nm). Displacement was measured by three
orthogonally positioned accelerometers mounted on the cylinder. Stimulation with
the mini-shakers did not permit determination of the excitatory direction along the
designated axis, so all directional response pattern (DRP) illustrations consist of the
best axis without regard to the excitatory versus inhibitory segment. In other words,
although the DRPs for cells look like the cosine function of a single hair cell (Fig.
1a), the actual excitatory direction is not known, only the best axis (see Fay and
Edds-Walton 1997a for a detailed explanation of the DRPs).
The fish was positioned in a custom head-holder within the cylindrical dish containing chilled seawater at a depth sufficient to submerge the gills. The dorsal surface of the fish was covered with a paper towel in contact with the water surface so
that the entire body was kept moist, but the surgical area was free of water. An
P.L. Edds-Walton
were included in data sets. The care and use of the toadfish during experimentation
was approved by the IACUC at the MBL and at Loyola University Chicago, Parmly
Hearing Institute.
2.2 Tract-Tracing
The tract-tracing studies included a variety of methods and labels, including DiI
(1,1 dio-octadecyl 3,3,3,3 tetramethyl-indocarbocyanine-perchlorate, Sigma), biotinylated dextran amines (rhodamine, fluoroscein, cascade blue; 3000 and 10,000
MW, Molecular Probes), and neurobiotin (Molecular Probes). Details of the neuranatomical methods may be found in Edds-Walton (1998a, b), Edds-Walton et al.
(1999), and Edds-Walton and Fay (2005a).
2.3 Physiology
All physiological studies were conducted using stimuli produced by the “shaker
system” designed by Fay and described in detail in Fay and Edds-Walton (1997a, b).
This unique stimulus system provides a particle-motion dominated sound field that
is well controlled and predictable. The shaker system consists of a vibrationisolated, open cylinder attached to a single vertical shaker (beneath the cylinder)
and paired mini-shakers (front–back and side–side stimulation). The shaker system
is programmed (and calibrated daily) to provide particle motion stimulation at specified frequencies (50–300 Hz) along designated axes in the horizontal and mid-
sagittal planes (0°, 30°, 60°, 90°, 120°, 150°). Particle motion is a vector quantity
with direction, frequency, and magnitude, and it is the component of sound to which
all fish ears respond (Fay 2005; Popper and Fay 2011; Radford et al. 2012). Simply,
each stimulus (500 ms duration, 20 ms rise, fall; repeated 8 times) consisted of controlled movement along a single axis in a single plane (see Fig. 3 in Edds-Walton
and Fay 2008) to simulate particle motion produced by a sinusoid at a single frequency and designated level (dB re: 1 nm). Displacement was measured by three
orthogonally positioned accelerometers mounted on the cylinder. Stimulation with
the mini-shakers did not permit determination of the excitatory direction along the
designated axis, so all directional response pattern (DRP) illustrations consist of the
best axis without regard to the excitatory versus inhibitory segment. In other words,
although the DRPs for cells look like the cosine function of a single hair cell (Fig.
1a), the actual excitatory direction is not known, only the best axis (see Fay and
Edds-Walton 1997a for a detailed explanation of the DRPs).
The fish was positioned in a custom head-holder within the cylindrical dish containing chilled seawater at a depth sufficient to submerge the gills. The dorsal surface of the fish was covered with a paper towel in contact with the water surface so
that the entire body was kept moist, but the surgical area was free of water. An
P.L. Edds-Walton