The swim bladder is considered to affect mainly the amplitude of a signal,
although it may yet contribute to other features of species-specific signals,
including harmonic structure (see Demski et al. 1973; Kalmijn 1988;
Hawkins 1993). Harmonics may prove to be an important component of
signaling in shallow waters to increase call detection via increased energy
56
A.H. Bass and C.W. Clark
Grunt train
Fictive grunt train
Olfactory
bulb
Olfactory
nerve
Optic
nerve
Sonic
occipital
nerve
Spinal cord
Pituitary
gland
Preoptic area -
anterior
hypothalamus
C e
r e b ellum
2 mm
1 s
5 ms
Electrical
stimulus
Midbrain
vocal neurons
Hindbrain
vocal neurons
Vocal pattern generator
Midbr a in
Medull a
F or eb ra in
Sonic
muscle
Figure 2.14. A side view of a plainfin midshipman fish showing a natural grunt train
(also see Fig. 2.12). An expanded view of the brain shows the location of neurophysiologically and anatomically identified brain sites that evoke a rhythmic, patterned output from a hindbrain vocal pattern generator (see Bass and Baker 1990;
Bass et al. 1994; Goodson and Bass 2000a). Each half of the SMN projects to the
ipsilateral sonic muscle attached to the lateral walls of the swim bladder via a ventral
sonic occipital nerve. The output of the hindbrain circuit can directly establish the
fundamental frequency and duration of a vocalization (Bass and Baker 1990).
Shown here are extracellular recordings from the surface of one occipital nerve.
Such recordings, referred to as fictive vocalizations, precisely mimic the temporal
structure of natural vocalizations, which in this case are grunts. For this experiment,
the anterior hypothalamus was electrically stimulated; each stimulus is followed by
a fictive grunt, which is a cluster of closely spaced nerve potentials that represent
the synchronous activity of the motoneurons on that side of the brain. Both sides
of the brain and hence both nerves and sonic muscles are simultaneously active (see
Bass and Baker 1990 and Goodson and Bass 2000a).
although it may yet contribute to other features of species-specific signals,
including harmonic structure (see Demski et al. 1973; Kalmijn 1988;
Hawkins 1993). Harmonics may prove to be an important component of
signaling in shallow waters to increase call detection via increased energy
56
A.H. Bass and C.W. Clark
Grunt train
Fictive grunt train
Olfactory
bulb
Olfactory
nerve
Optic
nerve
Sonic
occipital
nerve
Spinal cord
Pituitary
gland
Preoptic area -
anterior
hypothalamus
C e
r e b ellum
2 mm
1 s
5 ms
Electrical
stimulus
Midbrain
vocal neurons
Hindbrain
vocal neurons
Vocal pattern generator
Midbr a in
Medull a
F or eb ra in
Sonic
muscle
Figure 2.14. A side view of a plainfin midshipman fish showing a natural grunt train
(also see Fig. 2.12). An expanded view of the brain shows the location of neurophysiologically and anatomically identified brain sites that evoke a rhythmic, patterned output from a hindbrain vocal pattern generator (see Bass and Baker 1990;
Bass et al. 1994; Goodson and Bass 2000a). Each half of the SMN projects to the
ipsilateral sonic muscle attached to the lateral walls of the swim bladder via a ventral
sonic occipital nerve. The output of the hindbrain circuit can directly establish the
fundamental frequency and duration of a vocalization (Bass and Baker 1990).
Shown here are extracellular recordings from the surface of one occipital nerve.
Such recordings, referred to as fictive vocalizations, precisely mimic the temporal
structure of natural vocalizations, which in this case are grunts. For this experiment,
the anterior hypothalamus was electrically stimulated; each stimulus is followed by
a fictive grunt, which is a cluster of closely spaced nerve potentials that represent
the synchronous activity of the motoneurons on that side of the brain. Both sides
of the brain and hence both nerves and sonic muscles are simultaneously active (see
Bass and Baker 1990 and Goodson and Bass 2000a).