2. Bird Song & hearing 746 - Lecture 1

3. Aim nOutline the physiology of hearing and vocalisations u seasonal variation u developmental processes u the way this leads to dialects nhearing in owls u role in prey capture

4. Birdsong nWhat is a sonogram? u time on x axis; frequency on y axis u intensity shown by colour / black intensity/ time sonogram time  frequency 

5. Birdsong nEach species has its own song

6. Dialects nWhite-crowned sparrow

7. Isolated from sound njuveniles hear no sound will sing in spring

8. Play song to juveniles (I) nPlayed another species song only nRecord next spring song

9. Play song to juveniles (II)

10. Summary so far nDialects in many passerines nJuveniles learn father’s song u Prefer own species song u develop their own nNext: how is this achieved in brain?

11. Song brain map controls song only in song birds auditory input to area L Brainstem (bilateral coordination)

12. During singing nneed u HVc u RA nHVc activity precedes song by 50ms nStimulate HVc and disrupt singing nStimulate RA and disrupt singing nHVc can generate pattern on own

13. During learning nforebrain essential u LMAN u X nLMAN carries “jitter” needed in learning process

14. HVc neuron - own song intensity sonogram total count of spikes spike replicates

15. HVc neuron-synthetic song intensity sonogram total count of spikes spike replicates

16. Another synthetic song intensity sonogram total count of spikes

17. Summary of HVc expt nHVc is sensitive to own song nselective

18. During singing nnetwork via UVA & NIF acts a delay nproduces efference copy ncomparison with acoustic input nCheck that birds is singing “correctly”

19. Seasonality nCanaries add/replace syllables annually nHVc grows/shrinks annually u new neurons! ntestosterone causes u more growth in males u singing in females and castrati

20. Summary so far nBird song is complex behaviour nMany songs learnt u initial learning as juvenile u used as adult nHVc u controls motor output u responds to song pattern u possible site of song learning

21. Major impacts: u Neurons added to brain u Focused nuclei affected during learning u Male and female radically different

22. Owl hearing nProblem u locate mouse u 1) how far away u 2) which direction nimplies ability to locate mouse in x,y coordinates

23. Going... nTotal darkness nInfra-red picture

24. Behaviour Method  elevation  azimuth  mount high frequency coil on head in magnetic field

25. Results nError less than 5 o for most angles

26. Owl ears nare hidden behind facial ruff

27. Owl ears are asymmetric nLeft up nRight down

28. Sound at the 2 ears has: nTime difference u gets to further away ear later nITD nIntensity difference u quieter in auditory shadow nIID

29. How so accurate? nboth ears contribute to L/R and U/D

30. Neurons respond... nonly to one point in space count of spikes to sound

31. 2-d tonotopic map

32. Map generated from ? nIID u intensity coded by spikes; u summate at synapse nITD nJeffress hypothesis: u axon conduction delay u leads to coincidence

33. Jeffress hypothesis

34. N. laminaris

35. Time delay ncoincidence detection

36. Pathways IID pathway: orange ITD pathway: blue Local anaesthetic used to show separate pathways

37. Summary nAsymmetry of ears allows u ITD u IID nSeparation of intensity and time delay in CNS allows u tonotopic map u align to visual cortex nCatch mouse