behavioral plasticity CH8: development of learning in songbirds

behavioral analysis of birdsong singing in the brain summary

PART 4: BEHAVIORAL PLASTICITY#16: DEVELOPMENT OF LEARNING IN SONGBIRDS I

behavioral plasticity CH8: development of learning in songbirds

behavioral analysis of birdsong singing in the brain summary

PART 4: BEHAVIORAL PLASTICITY#16: DEVELOPMENT OF LEARNING IN SONGBIRDS I

adaptive responses to repeated experiences experience prediction of future events information learned, stored & later retrieved many forms, simple & complex experiences via all sensory modalities encoded in nervous system

cellular machinery neuronal networks behavioral plasticity ~ neural plasticity

nature - nurture

BEHAVIORAL PLASTICITY

vocal communication territory warning breeding ?

highly diverse songs studied to learn about

how animals communicate learning & memory

DEVELOPMENT OF LEARNING IN SONGBIRDS

birds 28 orders, 163 families, < 2000 genera, ~ 9000 spp. ~ 4000 songbird spp. most work on song done with 3 spp.

white-crowned sparrow (Zonotrichia leucophrys) zebra finch (Poephia guttata) canary (Serinus canaria)

DEVELOPMENT OF LEARNING IN SONGBIRDS

song mostly on perches (not ground)... more effective rich in sp.-specific & social information huge variety among bird spp.

1 invariant song ~ 100 songs geographic dialects

learning... for many spp. must hear sp.-specific song @ critical time normal development, under hormonal control

DEVELOPMENT OF LEARNING IN SONGBIRDS

systematics of birdsong began early (Darwin) lab studies in 1950s

methodology framed important questions

BEHAVIORAL ANALYSIS

accoustic structure time-frequency sound spectrograph visualize song consists of punctuated sound units

note or element = 1 continuous sound can have varied internal structure

syllable 2 notes phrase 2 syllables or

can be 1 syllable / note @ critical position syntax = timing, order, song specificity

WHAT’S IN A SONG ?

accoustic structure

WHAT’S IN A SONG ?

dialects (eg., white crowned sparrow) same song, different location

WHAT’S IN A SONG ?

vocalization mechanism respiration-driven... breathe between syllables sound from syrinx (~ human larynx) vibration of syringeal tympaniform membranes

WHAT’S IN A SONG ?

in many spp. only sing initial studies (chaffinch)

isolated young s played tapes of adult song observed that young s

could imitate recording of species-typical song no exposure songs very simple exposure as adult songs abnormal

learning by imitation @ specific age some birds (eg., canaries) not age-limited

open-ended learners

SONG LEARNING

stages of song learning similar in most songbirds temporal variation

1st, make subsong ~ baby talk part of development, only in spp. that learn

2nd, make plastic song 1st evidence of imitation & song rehearsal sp.-specific characteristics recognizable

SONG LEARNING

timing of learning, different phases, can overlap sensory: critical / sensitive, must hear song sensorimotor: subsong & plastic song phases crystalized: song fully developed

SONG LEARNING

duration & timing of phases varies age-limited learners (B), phases can overlap

SONG LEARNING

duration & timing of phases varies age-limited learners (B), phases can overlap seasonal-closed learners (A), phases separated

SONG LEARNING

may only learn as juveniles & recall...

duration & timing of phases varies age-limited learners (B), phases can overlap seasonal-closed learners (A), phases separated open-ended learners (C), overlap & repeat

SONG LEARNING

timing differences within same species, related to length of breeding season probably triggered by photoperiod

SONG LEARNING

critical period ~ 65 days in presence of father > 65 days in presence of s

what closes the learning-critical time window ? in Zebra finches...

SONG LEARNING

what closes the learning-critical time window ? critical period in Zebra finches...

~ 65 days in presence of father > 65 days in presence of s influence of tutors... live > taped

not fixed time window social interaction & tutor variation influence

sensitive rather than critical window flexibility

SONG LEARNING

imitation, improvisation & invention not purely imitation of father swamp sparrows ~ 200 syllables

1/3 imitated 36 improvised (variations) > 1/3 invented (novel)

imitated 1st improvised & invented later

SONG LEARNING

imitation, improvisation & invention creative process, can combine multiple songs

SONG LEARNING

imitation, improvisation & invention crystalized song is subset of plastic song syllables trial & error use ? action-based learning some birds may sing songs in the order they were learned

SONG LEARNING

what is learned during sensory phase ? studied with play-back of taped or synthetic songs

innate preferences species-specific > other

SONG LEARNING

what is learned during sensory phase ? studied with play-back of taped or synthetic songs

innate preferences sp.-specific > other song live non-specific > taped sp.-specific song non-specific father > live sp.-specific song but with

no visual... multimodal sensory critical – context sp.-specific > non-specific physiological response (eg., heart rate) – internal mechanism use innate + learned / experienced information

SONG LEARNING

learning a foreign song... what is not innate eg., sympatric sparrows, many song differences normal isolated tape-trained deaf

SONG LEARNING

learning a foreign song... what is not innate tape-trained... sp. specific > non mixed taped songs:

swamp sparrows used ~ syllable phonology song sparrows used syllable phonology, syntax

& song tempo... could learn swamp sparrow songs in their own syntax own syllables in swamp sparrow pattern but not normal swamp sparrow song

hear, articulate but use perceptual filter

SONG LEARNING

innate song... what is not learned isolated birds

sing abnormal songs some sing recognizable isolate or innate songs

eg., swamp sparrow can also learn rest of song

isolation not learning

SONG LEARNING

innate song... what is not learned aspects of innate songs develop normally > others

duration, tonality, frequency range OK syllables (words!) NOT

certain aspects of song innate, others learned repertoire size (# of songs) innate

SONG LEARNING

auditory feedback & song templates how does singing begin in sensorimotor phase ? feedback ?... test by deafening (remove cochlea)

before subsong... tutoring does not work accesses own memory through hearing auditory feedback critical

song template matching either innate or learned ! (... what... where... ?)

very different song from no song memory at all

isolated & deafened birds

SONG LEARNING

auditory feedback & song templates feedback ?...

initially thought not critical for song maintenance deafening after crystallization

no effect ?... after some time

syllables phonology of syllables changes

can be critical for development & maintenance

SONG LEARNING

in most songbirds... only s sing, sexual dimorphism neuronal basis of song ~ brain polymorphism ? in (eg., canaries) hormone levels correlated with

breeding season gonad size song, 1/~ new syllables castrated s do not

learn complete song

SEXUAL DIMORPHISM & HORMONAL REGULATION

steroid hormonal control s, stimulate song ~

s, repertoire

+ hormone crystallizes song – hormone loss ofcrystallized song

castrated s, retarded song development

SEXUAL DIMORPHISM & HORMONAL REGULATION

responses to hormonal treatment variable across spp. development of language learning in birds ~ humans

critical time windows stages dependent on auditory feedback

SEXUAL DIMORPHISM & HORMONAL REGULATION

BREAK