Bird Song (Lecture 13 & 14) Flashcards
Most studied songbirds
Canary, white crowned sparrow, zebra finch
Male –> Female songs can signal… (X5)
Presence of potential mate Individual identity Born and raised Physical location Owns territory
Song development stages
Subsong: rambling sounds, variable in timing and pattern
Plastic song: birds assume correct posture, produce sounds in discrete clusters. Contains aspects of temporal patterning of adult song. Rehearsal/imitation begins.
Crystallized song: full song with normal variations in volume, duration, syllabic structure etc.
Sensory and sensorimotor phase
Auditory experience occurs. Will memorise song but may not sing. Critical/sensitive period in which bird must hear normal species song.
Then enters sensorimotor phase (vocal practice, includes subsong and plastic song).
Isolated birds produce very different song. Can learn from tutor tapes (if played during critical phase)
Types of learners
Seasonal closed learner (sparrow): sensory and sensorimotor phase are distinct, song develops across the seasons.
Age limited learner (zebra finch): sensory and sensorimotor phases overlap. Song learned much faster (over days).
Seasonal open ended learner (canary): phases overlap, takes place across the seasons AND can go through multiple sensory phases even as adults - song can be adjusted e.g. to local changes.
Components of a song
Notes/elements: continuous marks on spectogram
Syllables: clusters of notes
Phrase: groups of 2/more syllables
Syntax: timing and ordering of all the above
Spectogram
Time along bottom, frequency up the side. Shows different components of a song.
Geographical location vs song
White crowned sparrows on west coast of america. Showed regional variations, known as dialects. Differences between golden gate park, brooks island and berkeley. Also showed differences in song learning stages.
Chipping sparrow also shown to have micro-dialects within single cemetery in massachusetts. After dispersal, young males would reject what they had learned from fathers and learn from male in future breeding location.
Chestnut-sided warblers: songs used to attract females highly conserved throughout geographic range of the species (throughout different states of the US). Male-male songs = highly localised micro-dialects
Songbird brain
Very similar brain regions in terms of language in humans/song production in birds.
Song production nuclei: HVc, RA (robust nucleus of the archistriatum), nXIIts. Parts of the MOTOR PATHWAY.
Song learning nuclei: area X, DLM (medial portion of dorsolateral thalamus), LMAN (lateral portion of magnocellular nucleus of the anterioir neostriatum). Parts of the ANTERIOR FOREBRAIN PATHWAY.
Both pathways are connected. Many areas absent in non-songbirds.
Song-selective neurons in auditory forebrain
Tuned to bird’s own song (respond better to own song than to conspecific’s).
Also respond worse to reversal of their own song (order is important).
Will also respond to motifs of the song. Combined motifs –> larger response.
Cross-fostering study
Zebra finches cross-fostered with Bengalese finch. Compared song syllables and gaps and recorded from primary auditory cortex (L3) neurons.
Found that temporal gap coding is innate (zebra finches had normal gaps) but syllable morphology is experience-dependent (zebra finches learned syllable morphology of foster species)
Distinct neuronal types for each: low and high firing (LF and HF). Both types respond to song and don’t respond to white noise (so song-specific). White noise that matches song in terms of temporal characteristics –> HF respond, LF don’t. Both respond to scrambled syllables of the real song.
HF encodes gaps, LF more to do with syllable morphology.
Reward Prediction Error
Juvenile birds have intrinsic template of song (probably genetically imprinted) which is updated through EXPERIENCE.
Reward prediction error is the difference between received and predicted reward (expectation vs outcome).
Involves dopaminergic neurons of area X: fire at baseline levels when received reward=predicted reward, fire more when MORE reward than expected and vice versa
Bird evaluates own song to produce auditory-error based reinforcement signal –> guides learning
Similar to reward signals shown in monkeys - dopaminergic neurons fire more when reward for behaviour is unexpectedly good
Test for performance error signals in birds
Study used zebrafinches. Artificially modulated song bird was hearing from own production –> bird adjusted to match own template.
Recorded from dopaminergic cells in VTA which projected –> area X (used retrograde tracer in X to ensure recording from neurons projecting to X).
Distorted a particular syllable 50% of the time. Dopaminergic firing increased when NOT distorted (distorted –> decreased or no firing)
ONLY the cells projecting to area X do this (not other VTA cells)
Responses also dependent on error probability: if distorted only 20% of the time, signal isn’t as strong. Suggests responses are evaluated for each syllable independently.
NO responses if bird is only listening to its song (and not producing song). Therefore nothing intrinsically “good” or “bad” about syllables - must be matched to own template
Where is song template stored?
Caudomedial Nidopallium (CMN) Lesion --> impairs ability to recognise tutor song but does NOT impair ability to produce song. Memory of tutor song and motor program for bird's own song therefore have separate neural representations.
Urban vs Rural environments
Experiment with great tits: looked at diff pops in urban (London, Paris) and rural environments. Found minimum frequency is higher in urban environment. Urban birds also had shorter duration first notes of a phrase. Urban songs also tended to be unusual (some urban songs had far more notes)
Higher frequency could be adaptive (result of higher background noise). BUT found to have no benefit in terms of communication in different environments. Probably just a result of having to sing at higher volume
