When the Brain is attending a cocktail party Rossitza Draganova

1. When the Brain is attending a cocktail partyRossitza Draganova

2. Cocktail Party Problem • The phenomenon how we do recognize what one person is saying or which instrument is playing, or who is singing when other sources around produce sounds at the same time is known as “cocktail party problem”, and introduced by Cherry, 1953 • Collecting knowledge of perceptual processes and internal sensory mechanisms underlying these phenomena are object of auditory scene analysis, Bregmann, 1990.

3. DEFINITIONS • Streaming – separated streams, fission • stream segregation -, the sound elements (frequency components) are assigned to different streams - two melodies • One stream – coherent auditory stream, fusion • stream integration – sound elements are bound into single stream of alternating low and high frequency tones – galloping rhythm • Isochronous sequence of tones – rhythmic single tone in a sequence

4. Triplets Paradigm A-B-A (Van Norden, 1975) • Presentation rate of A and B tone – SOA of A tones; SOA of B tones • The frequency difference between A and B tone - ∆f

5. Triplets Paradigm A-B-A (Van Norden, 1975) “1 stream with a galloping rhythm” Frequency … B B … … A A A A Time

6. “2 streams, one high and slow, the other low and fast” Frequency B B … … … A A A A Time

7. The build-up of auditory streaming:a systematic change in the auditory percept over timeduring prolonged listening to repeating sequences 1.0 0.8 1 ST 0.6 3 ST Probability '2 streams' response 6 ST 0.4 9 ST 0.2 0.0 0 1 2 3 4 5 6 7 8 9 Time (s)

8. TheperipheralchannelingtheoryHartmann and Johnson (1991) “1 stream” Level A B Frequency

9. “2 streams” Level A B Frequency

10. Build-up of segregation Horse Morse -LHL-LHL-LHL- --> --H---H---H-- -L-L-L-L-L-L-L • Segregation takes a few seconds to build up. • Then between-stream temporal / rhythmic judgments are very difficult

11. Streaming beyond Peripheral channeling • Hartmann and Johnson, (1991) - Peripheral Channeling • Vliegen, J. and Oxenham, A. J. (1999). "Sequential stream segregation in the absence of spectral cues," stream segregation between tones with same auditory excitation pattern, but different periodicities • Grimault et al., 2002 – Central mechanism, Difference between modulation rates, excluding spectral cues • Psychoacoustical studies identified different cues which influence the perceptual organization in stream segregation, (Moore & Gockel, 2002; Carlyon, 2004).

12. Neural basis of streaming • Neurons still in the AN respond to different frequencies. • Response to frequency of A • Response to frequency of B • Segregation on the base of frequency separation • Suppression mechanism (studies in monkeys) – primary auditory cortex

13. Suppression Mechanism

14. Neuromagnetic Correlates of Streaming in HumanAuditory Cortex. The Journal of Neuroscience, June 1, 2005 • 25(22):5382–5388 Alexander Gutschalk, Christophe Micheyl, Jennifer R. Melcher, Andre´ Rupp, Michael Scherg andAndrew J. Oxenham

15. Neuromagnetic Correlates of Streaming in HumanAuditory Cortex. The Journal of Neuroscience, June 1, 2005 • 25(22):5382–5388 Alexander Gutschalk, Christophe Micheyl, Jennifer R. Melcher, Andre´ Rupp, Michael Scherg andAndrew J. Oxenham

16. A – 250 ms (4 Hz) – pip - 500 Hz B - 500 ms (2Hz) – pip – 561Hz / 891Hz A – 166 ms – 6 Hz B – 333 ms – 3 Hz

17. Triplets Parameters 6sec 6 sec Pause – 3 s

18. Independent A – 200 ms (5 Hz) - 500Hz B – 500 ms (2Hz) - 561Hz / 891Hz

19. A – fc=650Hz; fm=110Hz B – fc=650Hz; fm=150 / 235 Hz

20. Right Ear B B A A Left Ear

22. Streaming based on central cues test signal length ISI CB – 4 Hz PB – 4 Hz Trial length 500 Hz 504 Hz 500 Hz + 504 Hz 500 Hz + 504 Hz

23. New methods for investigation of neural bases in streaming • New Paradigms • New stimuli – different stages in auditory system • Additional Neuronal correlates • New data analysis

24. New Paradigms • Peripheral neuronal mechanisms triplets, independent (temporal order) suppression mechanisms? Transient responses, SSR • Central neuronal mechanism • Primary stream segregation – build-up • Schema-based stream segregation – attention • Transition (influence of the context) – triplets • Transition – central beat vs. peripheral

25. New Stimuli • Peripheral stimuli – pure tones (pips, tone-bursts) • Binaural stimuli – still peripheral (interaural delay) • binaural – both ears corresponded to different peripheral channels (better presentation) • binaural – both ears have different locations (grouped as separate sources) • Peripheral is better as binaural (Deutsch, 1975) • Modulated stimuli – central mechanism • dichotic • Central beat vs. Peripheral beat – dichotic stimuli – central mechanism

26. Methods for Data analysis • Spectral analysis; • Time-frequency analysis – Wavelet; • Complex demodulation (Draganova et al., 1999); • Steady-State responses (SSR) • representation rate • (Periodicity analysis, R.Draganova, 1998); • SAM analysis • Transient responses (P1-N1-P2; SSF) • Source Analysis

27. Silent fMRI Paradigm Stimuli blocks 14 sec - TB 14 sec baseline BOLD response 4 sec Scan Scan 0 sec 32 sec 8 sec 16 sec 24 sec

28. fMRI Experiment 1 • Test Blocks • Two streams (Pure tones and AM tones, the same ∆f, different presentation rates) • Baseline • Galloping • Isochronous stream Experiment 2 • Test blocks • Central beat • Peripheral beat • Baseline • Continuous tone

29. Thank you for the attention !

30. Isochronous Stream