Seasonal changes in avian song control circuits do not cause seasonal changes in song discrimination in song sparrows

Reeves, Brendan J.; Beecher, Michael D.; Brenowitz, Eliot A.

doi:10.1002/neu.10257

Cited by 13 publications

(9 citation statements)

References 43 publications

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“…Song sparrows do not hoard food, and consistent with this observation, HP size does not vary seasonally in song sparrows (Lee et al, 2001). The NCM may function in song perception (Mello et al, 1992), which does not appear to vary seasonally in captive song sparrows (Reeves et al, 2001). Based on the above information, we hypothesized that androgen-metabolizing enzymes in the HP and NCM would not vary seasonally, making them useful "control" regions.…”

supporting

confidence: 56%

“…It is possible that hearing song up-regulates enzymes in NCM or, alternatively, that seasonal changes of enzymes in NCM produce changes in song perceptual abilities (Fusani et al, 2000). Song perception in captive male song sparrows does not appear to vary seasonally (Reeves et al, 2001), but neither wild nor molting birds have been examined. Local implants of aromatase inhibitors and/or estradiol to NCM would be an informative next step.…”

Section: Seasonal Changesmentioning

confidence: 98%

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Brain aromatase, 5α‐reductase, and 5β‐reductase change seasonally in wild male song sparrows: Relationship to aggressive and sexual behavior

et al. 2003

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In many species, territoriality is expressed only during the breeding season, when plasma testosterone (T) is elevated. In contrast, in song sparrows (Melospiza melodia morphna), males are highly territorial during the breeding (spring) and nonbreeding (autumn) seasons, but not during molt (late summer). In autumn, plasma sex steroids are basal, and castration has no effect on aggression. However, inhibition of aromatase reduces nonbreeding aggression, suggesting that neural steroid metabolism may regulate aggressive behavior. In wild male song sparrows, we examined the neural distribution of aromatase mRNA and seasonal changes in the activities of aromatase, 5 alpha-, and 5 beta-reductase, enzymes that convert T to 17 beta-estradiol, 5 alpha-dihydrotestosterone (5 alpha-DHT, a potent androgen), or 5 beta-DHT (an inactive metabolite), respectively. Enzyme activities were measured in the diencephalon, ventromedial telencephalon (vmTEL, which includes avian amygdala), caudomedial neostriatum (NCM), and the hippocampus of birds captured during spring, molt, or autumn. Aromatase and 5 beta-reductase changed seasonally in a region-specific manner. Aromatase in the diencephalon was higher in spring than in molt and autumn, similar to seasonal changes in male sexual behavior. Aromatase activity in the vmTEL was high in both spring and autumn but significantly reduced at molt, similar to seasonal changes in aggression. 5 beta-Reductase was not elevated during molt, suggesting that low aggression during molt is not a result of increased inactivation of androgens. These data highlight the relevance of neural steroid metabolism to the expression of natural behaviors by free-living animals.

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supporting

confidence: 56%

Section: Seasonal Changesmentioning

confidence: 98%

Brain aromatase, 5α‐reductase, and 5β‐reductase change seasonally in wild male song sparrows: Relationship to aggressive and sexual behavior

et al. 2003

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“…Male and female white-throated sparrows sing year-round (see Falls and Kopachena, 1994), and their auditory systems are presumably tuned to conspecific song regardless of season and sex steroid level. Using operant conditioning techniques, Reeves et al (2003) demonstrated that seasonal changes in day length and plasma levels of sex steroids do not affect the ability to discriminate between similar conspecific songs in another Emberizid, the song sparrow. The results we report here are not likely to indicate changes in discrimination ability or hearing sensitivity.…”

Section: Discussionmentioning

confidence: 99%

Topography of estradiol‐modulated genomic responses in the songbird auditory forebrain

Sanford

Lange

Maney

2009

Developmental Neurobiology

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Sex steroids facilitate dramatic changes in behavioral responses to sociosexual signals and are increasingly implicated in the sensory processing of those signals. Our previous work demonstrated that in female white-throated sparrows, which are seasonal breeders, genomic responses in the auditory forebrain are selective for conspecific song over frequency-matched tones only when plasma estradiol (E2) reaches breeding levels. Here, we sought to map this E2-dependent selectivity in the best-studied area of the auditory forebrain, the caudomedial nidopallium (NCM). Nonbreeding females with low endogenous levels of E2 were treated with E2 or a placebo and exposed to conspecific song, tones, or no sound playback. Immunoreactive protein product of the immediate early gene zenk (egr-1) was then quantified within seven distinct subregions, or domains, of NCM. We report three main findings: (1) regardless of hormone treatment, the zenk response is significantly higher in dorsal than in ventral NCM, and higher in medial than in lateral NCM; (2) E2-dependent selectivity of the response is limited to the rostral and medial domains of NCM; in the more caudal domains, song induces more zenk expression than tones regardless of hormone treatment; (3) even when no sound stimuli were presented, E2 treatment significantly increased zenk expression in the rostral, but not the caudal, domains of NCM. Together, the latter two findings suggest that E2-dependent plasticity in NCM is concentrated in rostral NCM, which is hodologically and neurochemically distinct from caudal NCM. Activity in rostral NCM may therefore be seasonally regulated in this species.

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“…Similarly, returning (ASY) male juncos may recognize the vocal behavior of some neighbors based on previous learning experience, resulting in their having less new auditory information to learn than SY males establishing boundaries with neighbors for the first time. One study that assessed the ability of Song Sparrows (Melospiza melodia) to discriminate between very similar conspecific songs, however, found no deficit in this ability in short photoperiod-exposed birds with regressed SCRs compared to long photoperiod-exposed birds with exogenous T and large SCRs, suggesting that large SCRs are not necessary for this task [Reeves et al, 2003].…”

Section: Age Differences In Brain and Behaviormentioning

confidence: 99%

Age-Related Difference in Size of Brain Regions for Song Learning in Adult Male Dark-Eyed Juncos <i>(Junco hyemalis)</i>

Corbitt

Deviche²

2005

Brain Behav Evol

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In seasonally breeding adult male songbirds, the volumes of several song control regions (SCRs) change seasonally in parallel with plasma testosterone (T) levels and decrease following gonadectomy. Testosterone treatment to castrates prevents this decrease, indicating T dependency. During the breeding season, second-year (SY: birds entering their first breeding season) free-ranging male Dark-eyed Juncos (Junco hyemalis) have smaller testes than older (after second-year, ASY: birds entering at least their second breeding season) birds. SY males also have lower plasma T concentrations than ASY males at the beginning of the breeding season. We investigated differences in song structure of the two age groups and the relationship between age differences in gonadal function and SCR sizes. The average number of syllables per song, syllable duration, trill rate, song duration, and variability in song duration were age-independent. Two brain regions that are thought to be involved primarily in song learning and perception were 13 and 18% larger, respectively, in SY than in ASY males, the opposite of what would be expected based solely on reproductive measures (testis mass and cloacal protuberance width). In contrast, the volumes of two regions that directly control song expression did not differ with age. The lack of age-related size differences in regions that are required for song production may indicate that male juncos of all ages have similar brain space requirements for motor production. Where there were size differences, they were restricted to regions primarily controlling vocal behavior acquisition/perception, suggesting that first time breeders need more brain space than experienced breeders to acquire crystallized song and/or acoustically perceive aspects of their environment.

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Seasonal changes in avian song control circuits do not cause seasonal changes in song discrimination in song sparrows

Cited by 13 publications

References 43 publications

Brain aromatase, 5α‐reductase, and 5β‐reductase change seasonally in wild male song sparrows: Relationship to aggressive and sexual behavior

Brain aromatase, 5α‐reductase, and 5β‐reductase change seasonally in wild male song sparrows: Relationship to aggressive and sexual behavior

Topography of estradiol‐modulated genomic responses in the songbird auditory forebrain

Age-Related Difference in Size of Brain Regions for Song Learning in Adult Male Dark-Eyed Juncos <i>(Junco hyemalis)</i>

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