159
may be the only means available to study hearing because alternative methods such
as auditory electrophysiology require surgical preparation; this preparation prevents
the use of many species that are sensitive and less stress tolerant to the surgery
required for invasive auditory physiology experiments. Another advantage of using,
noninvasive behavioral methods is that they can be used to test hearing capabilities
of fi sh in longitudinal studies, which is useful in determining the onset and development of hearing in a given species. Finally, auditory evoked behaviors require the
integration of multiple circuits and higher order auditory processing to produce a
reliable and behaviorally relevant response. Thus, the use of auditory evoked behaviors provides an inherently sensitive way to assess hearing.
Why are behavioral methods important in understanding auditory function in
fi shes? Because hearing capability is often directly related to a behaviorally relevant
function of an animal, it should follow that any stimulus that can evoke a behavioral
change is a “relevant” stimulus to that animal. When considering the use of behaviorally relevant stimuli, researchers must use auditory stimulus parameters that take
into account the hearing range of the species of interest. For example, in determining an audiogram for a fi sh species with no known hearing specializations, the use
of stimulus frequencies greater than 2 kHz (roughly the upper frequency limit of
sound–pressure sensitive fi sh) would often be superfl uous, except in cases where
fi shes might be sensitive to ultrasound (>20 kHz). However, researchers should also
be cautious to keep stimulus parameters relatively broad in order to conservatively
assess the complete range of auditory capability in a given species. As Popper and
Fay ( 1993 ) stated in their infl uential review on sound detection and processing in
fi sh “…we could say that all objects that may produce or scatter sound simultaneously are equally ‘biologically signifi cant’, in the sense that no source can be identifi ed or localized without signifi cant processing of the simultaneous sounds from the
other sources.”
In general, electrophysiology has been the most commonly used technique during the past 30 years to assess the auditory capabilities of fi shes. Techniques such as
single neuron recordings, auditory evoked potential (AEPs, also referred to in previous literature as the auditory brainstem response, or ABR), and microphonic potential recordings have been instrumental in understanding various auditory capabilities
of fi shes including temporal encoding (Fay 1978a ; Fay and Coombs 1983; Bodnar
and Bass 1997 ; Kozloski and Crawford 2000 ), frequency selectivity (Fay and EddsWalton 1997 ; Weeg et al. 2002 ), auditory plasticity (Sisneros and Bass 2003 ;
Sisneros 2009 ), directional sensitivity (Enger et al. 1973 ; Lu et al. 1996 ; Fay and
Edds-Walton 2000 ; Edds-Walton and Fay 2003 ), and the role of inhibition in shaping frequency tuning properties and phase locking ability (Fay 1978b ; Fay 1995 ;
Kawasaki and Guo 1998 ; McKibben and Bass 1999 ; Maruska and Tricas 2009 ).
These methods are rapid and precise compared to behavioral methods, and as a
result, they have been the technique of choice to investigate the hearing abilities of
fi sh since the early 1960s (Enger 1963 ; Furukawa and Ishii 1967 ).
Although electrophysiological methods are critical in the study of fi sh hearing,
they do have some limitations. First, some methods, like single auditory neuron and
microphonic potential recordings, are technically diffi cult to perform, can involve
Revisiting Psychoacoustic Methods for the Assessment of Fish Hearing
may be the only means available to study hearing because alternative methods such
as auditory electrophysiology require surgical preparation; this preparation prevents
the use of many species that are sensitive and less stress tolerant to the surgery
required for invasive auditory physiology experiments. Another advantage of using,
noninvasive behavioral methods is that they can be used to test hearing capabilities
of fi sh in longitudinal studies, which is useful in determining the onset and development of hearing in a given species. Finally, auditory evoked behaviors require the
integration of multiple circuits and higher order auditory processing to produce a
reliable and behaviorally relevant response. Thus, the use of auditory evoked behaviors provides an inherently sensitive way to assess hearing.
Why are behavioral methods important in understanding auditory function in
fi shes? Because hearing capability is often directly related to a behaviorally relevant
function of an animal, it should follow that any stimulus that can evoke a behavioral
change is a “relevant” stimulus to that animal. When considering the use of behaviorally relevant stimuli, researchers must use auditory stimulus parameters that take
into account the hearing range of the species of interest. For example, in determining an audiogram for a fi sh species with no known hearing specializations, the use
of stimulus frequencies greater than 2 kHz (roughly the upper frequency limit of
sound–pressure sensitive fi sh) would often be superfl uous, except in cases where
fi shes might be sensitive to ultrasound (>20 kHz). However, researchers should also
be cautious to keep stimulus parameters relatively broad in order to conservatively
assess the complete range of auditory capability in a given species. As Popper and
Fay ( 1993 ) stated in their infl uential review on sound detection and processing in
fi sh “…we could say that all objects that may produce or scatter sound simultaneously are equally ‘biologically signifi cant’, in the sense that no source can be identifi ed or localized without signifi cant processing of the simultaneous sounds from the
other sources.”
In general, electrophysiology has been the most commonly used technique during the past 30 years to assess the auditory capabilities of fi shes. Techniques such as
single neuron recordings, auditory evoked potential (AEPs, also referred to in previous literature as the auditory brainstem response, or ABR), and microphonic potential recordings have been instrumental in understanding various auditory capabilities
of fi shes including temporal encoding (Fay 1978a ; Fay and Coombs 1983; Bodnar
and Bass 1997 ; Kozloski and Crawford 2000 ), frequency selectivity (Fay and EddsWalton 1997 ; Weeg et al. 2002 ), auditory plasticity (Sisneros and Bass 2003 ;
Sisneros 2009 ), directional sensitivity (Enger et al. 1973 ; Lu et al. 1996 ; Fay and
Edds-Walton 2000 ; Edds-Walton and Fay 2003 ), and the role of inhibition in shaping frequency tuning properties and phase locking ability (Fay 1978b ; Fay 1995 ;
Kawasaki and Guo 1998 ; McKibben and Bass 1999 ; Maruska and Tricas 2009 ).
These methods are rapid and precise compared to behavioral methods, and as a
result, they have been the technique of choice to investigate the hearing abilities of
fi sh since the early 1960s (Enger 1963 ; Furukawa and Ishii 1967 ).
Although electrophysiological methods are critical in the study of fi sh hearing,
they do have some limitations. First, some methods, like single auditory neuron and
microphonic potential recordings, are technically diffi cult to perform, can involve
Revisiting Psychoacoustic Methods for the Assessment of Fish Hearing