Download Organization of Song Learning

Organization of Song Learning
Neurophysiological Map of Song Learning
Test involvement of RA in song
production
• Ablate RA or RA projections to nXIIts
– Males do not sing
• Sexual dimorphism in RA?
Male
Female
Role of lMAN in Song Learning
• Ablate lMAN
– Adulthood: no effect on already learned song
– Juvenile: inability to produce a normal song in
adulthood
• Compare lMAN in birds that learn songs to
birds that vocalize but don’t learn
– lMAN is smaller/absent in non-learners
Role of HVC
Role of HVC
• Size of HVC is significantly correlated with size
of song repertoire
Pfaff et al 2007
Assumptions
• Size is a critical determinant of function
– Does large HVC lead to ability to learn many songs
or does learning many songs lead to increase in
HVC size?
Leitner et al 2002
Distinct Songs
Why do birds sing distinct songs?
• Attract mates of the same species
• Repel males of the same species who might
try to ‘steal’ territory or females
• Species Identification Hypothesis
• Consider costs of song learning
Singing repels would be invaders
Singing attracts females
Why do some birds learn songs?
• Only 3 orders of singing birds exist (of 23 total)
• Hypothesis: to fine tune the song to a particular
habitat
– Low frequency travels well, degrades less in dense
foliage/forest/jungle
– High frequency travels best in open environment or a city,
where they don’t compete with rumbling trucks, exhaust,
etc.
• Hypothesis: to signal fitness to neighbors
– Matching songs to close neighbors indicates ‘sameness’
as well as fitness, providing a signal to accept one’s
presence and conserve resources by not fighting
Using songs to communicate
• Males signal high aggressiveness by singing an
exact match to a song in his neighbor’s
repertoire
• Males signal low to moderate aggressiveness
by singing a related song
• Males essentially sign a non-compete
agreement when they sing a totally unrelated
song from their neighbor
Implications: Males that hold territory for years should have
more shared songs with their neighbors, and they do. Males that
move around a lot lack any kind of song matching or dialect.
Female directed song
How/Why do females arrive at a song
preference?
• Based on birth place dialect?
• Based on mastery of current local dialect?
– In either case the advantage would be of mating
with a male who could pass on the genes
necessary to thrive in the ‘right’ habitat.
• Developmental history?
– More complex song=larger HVC, larger fat
reserves, more robust immune system
– More complex song=fitter bird, better parental
care, food procurement,
Effect of good nourishment
Females differentiate good and poor
singing ability
Females use song quality to judge
male health and fitness
Control
Stressed
Female Behavior
• Females may also prefer:
– Faster songs
– Higher frequency songs
– Difficult songs (trilling)
• Song preference can be linked to expression of
the gene, ZENK, in the female caudomedial
mesopallidum (CMM)
– High levels when hearing the directed song
– Low levels when hearing the undirected song
DQ
• What features of birdsong are shared with
human speech?
• What hypotheses are suggested, based on
these similarities, for the proximate bases of
human language learning—genetic and
developmental components?
• What is the adaptive value of language for our
species?