2.3.3.2. Auditory Responses in HVc
Neurons in HVc show auditory responses; in particular, they exhibit selective responses to the bird’s own song compared with conspecific or
parametrically modified songs (Katz and Gurney 1981; McCasland and
Konishi 1981; Margoliash 1983, 1986, 1987; Margoliash and Konishi 1985;
Margoliash and Fortune 1992; Volman 1993; Lewicki 1996; Yu and Margoliash 1996; Theunissen and Doupe 1998; Mooney 2000). The selective
responses of song-system neurons have motivated the hypothesis that HVc
and the AFP may be involved in production-independent perceptual processing of songs that is influenced by representations of a bird’s own song
(Margoliash 1986, 1987). This hypothesis suggests developmental linkage of
responses to a bird’s own song with motor output, without invoking direct
motor processing during perception.
Studies of HVc-lesioned female canaries are consistent with a role
for HVc in song perception. Lesions to HVc abolish female behavioral
preferences for conspecific over heterospecific song (Brenowitz 1991) and
for sexually attractive song phrases over other phrases of conspecific
song (Del Negro et al. 1998; and see Vallet and Kreutzer 1995). That
is, although only conspecific song elicits copulation displays in prelesion females, all songs (conspecific and heterospecific) elicit solicitations
following HVc lesions. Multiunit recordings from HVc in sexually
receptive female canaries have identified inhibition that is restricted to
presentations of sexually attractive conspecific song phrases (Del Negro
et al. 2000). Thus, there may be a linkage between physiological inhibition
and that observed in behavior. Because the projection of area X onto
DLM (Fig. 7.3) is probably inhibitory (Luo and Perkel 1999), this suggests an overall release from inhibition in the rest of the AFP (DLM and
lMAN) that is proportional to the response in HVc. In female canaries,
the degree of release would be proportional to the sexual potency of the
stimulus.
The role of HVc in song discrimination may be species-dependent. In
both male and female starlings, HVc lesions do not affect the retention of
learned conspecific song discriminations but do affect the ability to form
new associations with familiar songs (Gentner et al. 2000). In contrast to
the studies in canaries and starlings, in female zebra finches, Taeniopygia
guttata, lesions to HVc have no effect on copulation solicitations (MacDougall-Shackleton et al. 1998a). Qualitative differences in sexual dimorphism between zebra finches and other species, especially the magnitude of
HVc projections onto RA and area X, may help to explain these differences
(Nottebohm and Arnold 1976; Gurney 1981). The data suggest that rather
than providing a direct role in perceptual representation, HVc may be
acting as a selective filter regulating motor control of subsequent behaviors, including copulation responses in females and song output in males.
Under this hypothesis, HVc filtering, and hence the perceptual processing
348
T.Q. Gentner and D. Margoliash
Neurons in HVc show auditory responses; in particular, they exhibit selective responses to the bird’s own song compared with conspecific or
parametrically modified songs (Katz and Gurney 1981; McCasland and
Konishi 1981; Margoliash 1983, 1986, 1987; Margoliash and Konishi 1985;
Margoliash and Fortune 1992; Volman 1993; Lewicki 1996; Yu and Margoliash 1996; Theunissen and Doupe 1998; Mooney 2000). The selective
responses of song-system neurons have motivated the hypothesis that HVc
and the AFP may be involved in production-independent perceptual processing of songs that is influenced by representations of a bird’s own song
(Margoliash 1986, 1987). This hypothesis suggests developmental linkage of
responses to a bird’s own song with motor output, without invoking direct
motor processing during perception.
Studies of HVc-lesioned female canaries are consistent with a role
for HVc in song perception. Lesions to HVc abolish female behavioral
preferences for conspecific over heterospecific song (Brenowitz 1991) and
for sexually attractive song phrases over other phrases of conspecific
song (Del Negro et al. 1998; and see Vallet and Kreutzer 1995). That
is, although only conspecific song elicits copulation displays in prelesion females, all songs (conspecific and heterospecific) elicit solicitations
following HVc lesions. Multiunit recordings from HVc in sexually
receptive female canaries have identified inhibition that is restricted to
presentations of sexually attractive conspecific song phrases (Del Negro
et al. 2000). Thus, there may be a linkage between physiological inhibition
and that observed in behavior. Because the projection of area X onto
DLM (Fig. 7.3) is probably inhibitory (Luo and Perkel 1999), this suggests an overall release from inhibition in the rest of the AFP (DLM and
lMAN) that is proportional to the response in HVc. In female canaries,
the degree of release would be proportional to the sexual potency of the
stimulus.
The role of HVc in song discrimination may be species-dependent. In
both male and female starlings, HVc lesions do not affect the retention of
learned conspecific song discriminations but do affect the ability to form
new associations with familiar songs (Gentner et al. 2000). In contrast to
the studies in canaries and starlings, in female zebra finches, Taeniopygia
guttata, lesions to HVc have no effect on copulation solicitations (MacDougall-Shackleton et al. 1998a). Qualitative differences in sexual dimorphism between zebra finches and other species, especially the magnitude of
HVc projections onto RA and area X, may help to explain these differences
(Nottebohm and Arnold 1976; Gurney 1981). The data suggest that rather
than providing a direct role in perceptual representation, HVc may be
acting as a selective filter regulating motor control of subsequent behaviors, including copulation responses in females and song output in males.
Under this hypothesis, HVc filtering, and hence the perceptual processing
348
T.Q. Gentner and D. Margoliash