166
stream segregation. Similar conditioning protocols using a complex stimulus and
analysis of the components have also been used to study pitch perception in goldfi sh (Fay 1995 ).
3 Use of Innate Behavioral Responses in Psychoacoustic
Studies of Fish Hearing
Many psychoacoustic studies of fi sh hearing have taken advantage of using innate
behavioral responses to assess the auditory capabilities of fi shes. Innate behavioral
responses are regarded as genetically programmed responses to external stimuli.
These stereotyped innate responses can often be used to probe an animal’s perceptual world or “umwelt” and characterize an animal’s sensory capabilities. Simple
refl ex responses and the more coordinated movement of refl exive locomotion are
two broad categories of innate behavioral responses that have been successfully
used to assess hearing in fi shes.
3.1 Refl ex Responses
Refl exes are involuntary movements in response to a sensory stimulus. Innate refl ex
responses are often used in psychoacoustic studies of hearing because they are stereotyped, repeatable and do not require conditional behavioral training in order to
evoke them. Furthermore, these conserved innate responses serve a behaviorally
relevant function, and are therefore robust and can be elicited easily. This allows for
very fast and effi cient measures of auditory capability.
3.1.1 Acoustic Startle Response
The most common refl ex response described across multiple species is the auditory
startle response (ASR). Although variants of the ASR have been described since
Aristotle, Wilson ( 1959 ) was the fi rst to show that the “tail-fl ip” startle response in
fi sh was driven by Mauthner cells (M-cells), giant neurons found in the fourth segment of the reticulospinal formation of the hindbrain (R4). This stereotyped startle
response is described in mammals (Parham and Willott 1988 ), anurans (Cioni et al.
1989 ), and urodeles (Marini et al. 1991 ). In fi sh, as well as anurans and urodeles, the
M-cell circuitry is relatively simple (Zottoli and Faber 2000 ). Briefl y, afferent neurons of the VIIIth nerve synapse onto the lateral dendrite of the M-cell. The M-cells
cross-over and innervate the motor neurons on the contralateral side of the fi sh.
When activated, an M-cell fi res a single spike that activates all the motor neurons on
the contralateral side of the fi sh, causing the fi sh to bend and accelerate away from
the direction of the stimulus. The startle-escape response was later formalized as the
A.A. Bhandiwad and J.A. Sisneros
stream segregation. Similar conditioning protocols using a complex stimulus and
analysis of the components have also been used to study pitch perception in goldfi sh (Fay 1995 ).
3 Use of Innate Behavioral Responses in Psychoacoustic
Studies of Fish Hearing
Many psychoacoustic studies of fi sh hearing have taken advantage of using innate
behavioral responses to assess the auditory capabilities of fi shes. Innate behavioral
responses are regarded as genetically programmed responses to external stimuli.
These stereotyped innate responses can often be used to probe an animal’s perceptual world or “umwelt” and characterize an animal’s sensory capabilities. Simple
refl ex responses and the more coordinated movement of refl exive locomotion are
two broad categories of innate behavioral responses that have been successfully
used to assess hearing in fi shes.
3.1 Refl ex Responses
Refl exes are involuntary movements in response to a sensory stimulus. Innate refl ex
responses are often used in psychoacoustic studies of hearing because they are stereotyped, repeatable and do not require conditional behavioral training in order to
evoke them. Furthermore, these conserved innate responses serve a behaviorally
relevant function, and are therefore robust and can be elicited easily. This allows for
very fast and effi cient measures of auditory capability.
3.1.1 Acoustic Startle Response
The most common refl ex response described across multiple species is the auditory
startle response (ASR). Although variants of the ASR have been described since
Aristotle, Wilson ( 1959 ) was the fi rst to show that the “tail-fl ip” startle response in
fi sh was driven by Mauthner cells (M-cells), giant neurons found in the fourth segment of the reticulospinal formation of the hindbrain (R4). This stereotyped startle
response is described in mammals (Parham and Willott 1988 ), anurans (Cioni et al.
1989 ), and urodeles (Marini et al. 1991 ). In fi sh, as well as anurans and urodeles, the
M-cell circuitry is relatively simple (Zottoli and Faber 2000 ). Briefl y, afferent neurons of the VIIIth nerve synapse onto the lateral dendrite of the M-cell. The M-cells
cross-over and innervate the motor neurons on the contralateral side of the fi sh.
When activated, an M-cell fi res a single spike that activates all the motor neurons on
the contralateral side of the fi sh, causing the fi sh to bend and accelerate away from
the direction of the stimulus. The startle-escape response was later formalized as the
A.A. Bhandiwad and J.A. Sisneros