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Bird Song & hearing 746 - Lecture 1 Aim Outline the physiology of hearing and vocalisations seasonal variation developmental processes the way this leads to dialects hearing in owls role in prey capture Birdsong What is a sonogram? time on x axis; frequency on y axis intensity shown by colour / black frequency intensity/ time sonogram time Birdsong Each species has its own song Dialects White-crowned sparrow Isolated from sound juveniles hear no sound will sing in spring Play song to juveniles (I) Played another species song only Record next spring song Play song to juveniles (II) Summary so far Dialects in many passerines Juveniles learn father’s song Prefer own species song develop their own Next: how is this achieved in brain? Song brain map only in song birds auditory input to area L Brainstem (bilateral coordination) controls song During singing need HVc RA HVc activity precedes song by 50ms Stimulate HVc and disrupt singing Stimulate RA and disrupt singing HVc can generate pattern on own During learning forebrain essential LMAN X LMAN carries “jitter” needed in learning process HVc neuron - own song spike replicates total count of spikes sonogram intensity HVc neuron-synthetic song spike replicates total count of spikes sonogram intensity Another synthetic song total count of spikes sonogram intensity Summary of HVc expt HVc is sensitive to own song selective During singing network via UVA & NIF acts a delay produces efference copy comparison with acoustic input Check that birds is singing “correctly” Seasonality Canaries add/replace syllables annually HVc grows/shrinks annually new neurons! testosterone causes more growth in males singing in females and castrati Summary so far Bird song is complex behaviour Many songs learnt initial learning as juvenile used as adult HVc controls motor output responds to song pattern possible site of song learning Major impacts: Neurons added to brain Focused nuclei affected during learning Male and female radically different Owl hearing Problem locate mouse 1) how far away 2) which direction implies ability to locate mouse in x,y coordinates Going ... Total darkness Infra-red picture Behaviour Method azimuth elevation mount high frequency coil on head in magnetic field Results Error less than 5o for most angles Owl ears are hidden behind facial ruff Owl ears are asymmetric Left up Right down Sound at the 2 ears has: Time difference gets to further away ear later ITD Intensity difference quieter in auditory shadow IID How so accurate? both ears contribute to L/R and U/D Neurons respond... only to one point in space count of spikes to sound 2-d tonotopic map Map generated from ? IID intensity coded by spikes; summate at synapse ITD Jeffress hypothesis: axon conduction delay leads to coincidence Jeffress hypothesis N. laminaris Time delay coincidence detection Pathways IID pathway: orange ITD pathway: blue Local anaesthetic used to show separate pathways Summary Asymmetry of ears allows ITD IID Separation of intensity and time delay in CNS allows tonotopic map align to visual cortex Catch mouse