160
invasive surgeries, and require physical restraint of the animal. Even noninvasive
methods, such as the AEP recording technique, which has been used in over 100 fi sh
species (Ladich and Fay 2013 ), require the animal to be physically restrained.
Unfortunately, some fi sh species are diffi cult to test using electrophysiological
methods due to a reduced tolerance for restraint, surgery, or other invasive methods.
Second, electrophysiological methods are often diffi cult to perform on small animals, especially those that are early in development and less stress-tolerant.
Although microphonic potentials have been recorded from larval fi sh (Lu and
DeSmidt 2013 ; Inoue et al. 2013 ), most other electrophysiological recording methods are technically challenging to perform on embryonic and larval fi shes. This
limitation reduces the ontogenetic stages and the age/size ranges that can be compared and makes developmental physiology studies more diffi cult to perform. Third,
electrophysiological methods such as the AEP recording technique that are used to
measure auditory thresholds are diffi cult to compare to behavioral measures of
hearing and are even more diffi cult to interpret in the context of natural auditory
driven behaviors (Ladich and Fay 2013 ; Sisneros et al. 2015 ). Microphonic potentials of the fi sh inner ear, for example, can only inform us of hair cell activity, but
not whether this activity results in an auditory percept for these fi shes. Thus, there
is a gap in our understanding of the relationship between behavioral and electrophysiological thresholds; although some correlations have been described for electrophysiological and behavioral thresholds, these correlations have only been made
for goldfi sh ( Carassius auratus ) with no single representative relation between
behavioral and physiological measures of auditory sensitivity (Ladich and Fay
2013 ). Variation of auditory thresholds obtained by electrophysiological measures
can often be related to such factors such as electrode placement, morphology of the
inner ear and skull, and the threshold criteria used.
This review primarily focuses on behavioral methods that are commonly used to
assess the hearing capabilities of fi shes. We discuss the use of associative (conditioning) methods and refl ex (innate) responses in psychoacoustic studies of fi sh
hearing. While many variants of these methods exist, we wish to convey the general
techniques used to assess hearing in fi shes and highlight the principles underlying
these techniques. We also discuss the benefi ts and limitations of various psychoacoustic methods used to assess fi sh hearing and emphasize the techniques that are
appropriate for investigating fundamental processes related to the sense of hearing
in fi shes.
2 Associative Methods
2.1 Operant Conditioning
Operant conditioning methods were used to study audition in fi shes soon after
Parker ( 1903 ) published his fi ndings that fi sh could detect acoustic stimuli. Operant
conditioning (also called instrumental conditioning) is a technique by which a
A.A. Bhandiwad and J.A. Sisneros
invasive surgeries, and require physical restraint of the animal. Even noninvasive
methods, such as the AEP recording technique, which has been used in over 100 fi sh
species (Ladich and Fay 2013 ), require the animal to be physically restrained.
Unfortunately, some fi sh species are diffi cult to test using electrophysiological
methods due to a reduced tolerance for restraint, surgery, or other invasive methods.
Second, electrophysiological methods are often diffi cult to perform on small animals, especially those that are early in development and less stress-tolerant.
Although microphonic potentials have been recorded from larval fi sh (Lu and
DeSmidt 2013 ; Inoue et al. 2013 ), most other electrophysiological recording methods are technically challenging to perform on embryonic and larval fi shes. This
limitation reduces the ontogenetic stages and the age/size ranges that can be compared and makes developmental physiology studies more diffi cult to perform. Third,
electrophysiological methods such as the AEP recording technique that are used to
measure auditory thresholds are diffi cult to compare to behavioral measures of
hearing and are even more diffi cult to interpret in the context of natural auditory
driven behaviors (Ladich and Fay 2013 ; Sisneros et al. 2015 ). Microphonic potentials of the fi sh inner ear, for example, can only inform us of hair cell activity, but
not whether this activity results in an auditory percept for these fi shes. Thus, there
is a gap in our understanding of the relationship between behavioral and electrophysiological thresholds; although some correlations have been described for electrophysiological and behavioral thresholds, these correlations have only been made
for goldfi sh ( Carassius auratus ) with no single representative relation between
behavioral and physiological measures of auditory sensitivity (Ladich and Fay
2013 ). Variation of auditory thresholds obtained by electrophysiological measures
can often be related to such factors such as electrode placement, morphology of the
inner ear and skull, and the threshold criteria used.
This review primarily focuses on behavioral methods that are commonly used to
assess the hearing capabilities of fi shes. We discuss the use of associative (conditioning) methods and refl ex (innate) responses in psychoacoustic studies of fi sh
hearing. While many variants of these methods exist, we wish to convey the general
techniques used to assess hearing in fi shes and highlight the principles underlying
these techniques. We also discuss the benefi ts and limitations of various psychoacoustic methods used to assess fi sh hearing and emphasize the techniques that are
appropriate for investigating fundamental processes related to the sense of hearing
in fi shes.
2 Associative Methods
2.1 Operant Conditioning
Operant conditioning methods were used to study audition in fi shes soon after
Parker ( 1903 ) published his fi ndings that fi sh could detect acoustic stimuli. Operant
conditioning (also called instrumental conditioning) is a technique by which a
A.A. Bhandiwad and J.A. Sisneros