210
filled contralateral somata in MON, indicating that there is a commissural tract that
provides the potential for integration of auditory (and lateral line) inputs from the
left and right sides of the fish (Edds-Walton et al. 2013). These data are consistent
with other studies of circuits that regulate body position in space (e.g., pitch and
roll), which also could include rapid responses to sound (discussed in Straka and
Baker 2011).
Although this review focuses on the directional hearing circuit, it is worth noting
that auditory input is combined with lateral line input in the midbrain of oyster
toadfish. Application of label to regions in the midbrain torus semicircularis (TS)
revealed sites where lateral line and auditory inputs converged (Edds-Walton and
Fay 2005b) and retrogradely filled projection cells were present in both DON and
the lateral line nucleus medialis. Consistent with the anatomy, physiological studies
confirmed bimodal cells in the TS that responded well to auditory particle motion
around 100 Hz, and to lateral line stimuli (water movement) ipsilaterally, or contralaterally, or on both sides of the fish (Fay and Edds-Walton 2001; Edds-Walton and
Fay 2005a). An additional finding was the presence of cells for which lateral line
stimulation inhibited the spiking activity during auditory stimulation (Edds-Walton
and Fay 2005a). Therefore, there are potentially interesting interactions between
these two sensory systems in toadfish, as well as other fishes (Braun and Sand
2014). The lateral line may be involved in orientation during the “final approach”
within centimeters of a sound source, rather than sound source localization from a
distance. A carefully conducted behavioral study with the closely related midshipman fish (Porichthys notatus, Batrachoididae) revealed that the lateral line is not
required for sound source localization by free-swimming females approaching a
speaker that projected male reproductive calls (Coffin et al. 2014).
3.3 Physiology: What the Ear Hears
Fay (1984) showed that all three otolithic endorgans in the goldfish responded to
particle motion at 140 Hz and each had directional responses that reflect the hair cell
orientations of that endorgan. Lu et al. (1998, 2003, 2004) also showed that all three
otolithic endorgans in the sleeper goby (Dormitator latifrons) can respond to similar
frequencies, however, the sound levels required to stimulate each endorgan varied to
the extent that all three are unlikely to be stimulated simultaneously.
Fay and Edds-Walton have focused on understanding auditory processing of the
saccule in the oyster toadfish, although an auditory role for the utricle or the lagena
have not been ruled out, nor have our physiological studies ruled out a potential role
for the saccule in orientation or equilibrium common for the vestibular systems of
other vertebrates. The potential for each otolithic endorgan to respond to low frequency linear acceleration associated with “vestibular” function and frequencies in
the auditory range, the “mixed function” hypothesis (Platt and Popper 1981; Popper
and Fay 1993), remains an intriguing possibility.
In 2011, Vasconcelos worked with another member of the Batrachoididae, the
Lusitanian toadfish (Halobatrachus didactylus), and used the shaker system to comP.L. Edds-Walton
filled contralateral somata in MON, indicating that there is a commissural tract that
provides the potential for integration of auditory (and lateral line) inputs from the
left and right sides of the fish (Edds-Walton et al. 2013). These data are consistent
with other studies of circuits that regulate body position in space (e.g., pitch and
roll), which also could include rapid responses to sound (discussed in Straka and
Baker 2011).
Although this review focuses on the directional hearing circuit, it is worth noting
that auditory input is combined with lateral line input in the midbrain of oyster
toadfish. Application of label to regions in the midbrain torus semicircularis (TS)
revealed sites where lateral line and auditory inputs converged (Edds-Walton and
Fay 2005b) and retrogradely filled projection cells were present in both DON and
the lateral line nucleus medialis. Consistent with the anatomy, physiological studies
confirmed bimodal cells in the TS that responded well to auditory particle motion
around 100 Hz, and to lateral line stimuli (water movement) ipsilaterally, or contralaterally, or on both sides of the fish (Fay and Edds-Walton 2001; Edds-Walton and
Fay 2005a). An additional finding was the presence of cells for which lateral line
stimulation inhibited the spiking activity during auditory stimulation (Edds-Walton
and Fay 2005a). Therefore, there are potentially interesting interactions between
these two sensory systems in toadfish, as well as other fishes (Braun and Sand
2014). The lateral line may be involved in orientation during the “final approach”
within centimeters of a sound source, rather than sound source localization from a
distance. A carefully conducted behavioral study with the closely related midshipman fish (Porichthys notatus, Batrachoididae) revealed that the lateral line is not
required for sound source localization by free-swimming females approaching a
speaker that projected male reproductive calls (Coffin et al. 2014).
3.3 Physiology: What the Ear Hears
Fay (1984) showed that all three otolithic endorgans in the goldfish responded to
particle motion at 140 Hz and each had directional responses that reflect the hair cell
orientations of that endorgan. Lu et al. (1998, 2003, 2004) also showed that all three
otolithic endorgans in the sleeper goby (Dormitator latifrons) can respond to similar
frequencies, however, the sound levels required to stimulate each endorgan varied to
the extent that all three are unlikely to be stimulated simultaneously.
Fay and Edds-Walton have focused on understanding auditory processing of the
saccule in the oyster toadfish, although an auditory role for the utricle or the lagena
have not been ruled out, nor have our physiological studies ruled out a potential role
for the saccule in orientation or equilibrium common for the vestibular systems of
other vertebrates. The potential for each otolithic endorgan to respond to low frequency linear acceleration associated with “vestibular” function and frequencies in
the auditory range, the “mixed function” hypothesis (Platt and Popper 1981; Popper
and Fay 1993), remains an intriguing possibility.
In 2011, Vasconcelos worked with another member of the Batrachoididae, the
Lusitanian toadfish (Halobatrachus didactylus), and used the shaker system to comP.L. Edds-Walton