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generated by a vibrating dipole source. Because the mechanoreceptive organs of
the lateral line are distributed over the fish’s head and body, van Bergeijk reasoned
that the lateral line system would be ideally suited to discriminate the near field
particle motion generated by a sound source and function in sound localization.
In addition, van Bergeijk (1967) also believed that lateral line organs were derived
from the same developing tissue (anlage) as the inner ear labyrinth and thus proposed that the lateral line and inner ear should be considered singular parts of an
“acoustico- lateralis” system. Based on these erroneous assumptions, van Bergeijk
(1967) introduced the “acoustic-lateralis” hypothesis in which he maintained that
the lateral line system and the inner ear otolithic end organs functioned together in
fish hearing, but only the lateral line was responsible for directional orientation and
source localization behaviors in fish.
At about this time, Moulton and Dixon (1967) reported an interesting set of
observations regarding the role of the inner ear in the escape response of the goldfish (Carassius auratus), which is similar to the minnow Phoxinus in that its swim
bladder is connected to the inner ear via Weberian ossicles. Goldfish innately exhibit
a rapid tail-flip escape reflex in response to an acoustic startle stimulus. In a series
of experiments, Moulton and Dixon (1967) conditioned goldfish using a food
reward to change the direction of the tail-flip escape response, which naturally
occurs in the opposite direction relative to the sound source. This orienting escape
reflex was assumed to be mediated by Mauthner cells located in the brain stem
(Furshpan and Furukawa 1962) but it was not experimentally confirmed. Fish were
conditioned to perform the tail-flip response toward the sound source for a food
reward. Pure tone signals of 100, 150, and 1500 Hz were used and the fish were
observed to perform the tail-flip response toward the sound source for all three
frequencies. Moulton and Dixon cleverly designed their experiments so that at
1500 Hz the sound source distance to the fish would be in the far field and well
beyond the extent of the near field as defined by Harris and van Bergeijk (1962).
When the authors severed the saccular and lagenar nerve (auditory inputs) on one
side, the conditioned fish responded as if the sound source was on the same side of
the intact nerve. Moulton and Dixon concluded that directional hearing is possible
using the inner ear end organs in the far field and that both ears (i.e., the binaural
processing of input from primarily the saccule and possibly the lagena) were
required for the directional tail-flip response.
2.3 Directional Hearing and Minimum Audible Angles
During the 1970s, Hawkins, Schuijf, Sand, Chapman, and their colleagues established behavioral evidence that a number of fish species were capable of directional
hearing and that fish could be conditioned to discriminate between sources of sound
that were spatially separated, and from opposing directions (Schuijf et al. 1971,
1977; Chapman 1973; Chapman and Johnstone 1974; Schuijf 1975; Schuijf and
Buwalda 1975; Hawkins and Sand 1977; Buwalda et al. 1983; Schuijf and Hawkins
Directional Hearing and Sound Source Localization in Fishes
generated by a vibrating dipole source. Because the mechanoreceptive organs of
the lateral line are distributed over the fish’s head and body, van Bergeijk reasoned
that the lateral line system would be ideally suited to discriminate the near field
particle motion generated by a sound source and function in sound localization.
In addition, van Bergeijk (1967) also believed that lateral line organs were derived
from the same developing tissue (anlage) as the inner ear labyrinth and thus proposed that the lateral line and inner ear should be considered singular parts of an
“acoustico- lateralis” system. Based on these erroneous assumptions, van Bergeijk
(1967) introduced the “acoustic-lateralis” hypothesis in which he maintained that
the lateral line system and the inner ear otolithic end organs functioned together in
fish hearing, but only the lateral line was responsible for directional orientation and
source localization behaviors in fish.
At about this time, Moulton and Dixon (1967) reported an interesting set of
observations regarding the role of the inner ear in the escape response of the goldfish (Carassius auratus), which is similar to the minnow Phoxinus in that its swim
bladder is connected to the inner ear via Weberian ossicles. Goldfish innately exhibit
a rapid tail-flip escape reflex in response to an acoustic startle stimulus. In a series
of experiments, Moulton and Dixon (1967) conditioned goldfish using a food
reward to change the direction of the tail-flip escape response, which naturally
occurs in the opposite direction relative to the sound source. This orienting escape
reflex was assumed to be mediated by Mauthner cells located in the brain stem
(Furshpan and Furukawa 1962) but it was not experimentally confirmed. Fish were
conditioned to perform the tail-flip response toward the sound source for a food
reward. Pure tone signals of 100, 150, and 1500 Hz were used and the fish were
observed to perform the tail-flip response toward the sound source for all three
frequencies. Moulton and Dixon cleverly designed their experiments so that at
1500 Hz the sound source distance to the fish would be in the far field and well
beyond the extent of the near field as defined by Harris and van Bergeijk (1962).
When the authors severed the saccular and lagenar nerve (auditory inputs) on one
side, the conditioned fish responded as if the sound source was on the same side of
the intact nerve. Moulton and Dixon concluded that directional hearing is possible
using the inner ear end organs in the far field and that both ears (i.e., the binaural
processing of input from primarily the saccule and possibly the lagena) were
required for the directional tail-flip response.
2.3 Directional Hearing and Minimum Audible Angles
During the 1970s, Hawkins, Schuijf, Sand, Chapman, and their colleagues established behavioral evidence that a number of fish species were capable of directional
hearing and that fish could be conditioned to discriminate between sources of sound
that were spatially separated, and from opposing directions (Schuijf et al. 1971,
1977; Chapman 1973; Chapman and Johnstone 1974; Schuijf 1975; Schuijf and
Buwalda 1975; Hawkins and Sand 1977; Buwalda et al. 1983; Schuijf and Hawkins
Directional Hearing and Sound Source Localization in Fishes