When the Brain is attending a cocktail party When the Brain is attending a cocktail party Rossitza Draganova

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.

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

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

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

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

Time (s) Probability '2 streams' response 1 ST 3 ST 6 ST 9 ST The build-up of auditory streaming: a systematic change in the auditory percept over time during prolonged listening to repeating sequences

The peripheral channeling theory Hartmann and Johnson (1991) Frequency A B “1 stream” Level

Frequency Level A B “2 streams”

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 Build-up of segregation

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).

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

Suppression Mechanism

Neuromagnetic Correlates of Streaming in Human Auditory Cortex. The Journal of Neuroscience, June 1, (22):5382–5388 Alexander Gutschalk, Christophe Micheyl, Jennifer R. Melcher, Andre´ Rupp, Michael Scherg and Andrew J. Oxenham

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

Triplets Parameters Pause – 3 s 6sec

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

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

Right Ear B B AA Left Ear

Streaming based on central cues 500 Hz504 Hz 500 Hz Hz ISI CB – 4 HzPB – 4 Hz Trial length test signal length

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

New Paradigms 1.Peripheral neuronal mechanisms triplets, independent (temporal order) suppression mechanisms? Transient responses, SSR 2. Central neuronal mechanism 3.Primary stream segregation – build-up 4.Schema-based stream segregation – attention 5.Transition (influence of the context) – triplets 6.Transition – central beat vs. peripheral

New Stimuli Peripheral stimuli – pure tones (pips, tone-bursts) Binaural stimuli – still peripheral (interaural delay) 1.binaural – both ears corresponded to different peripheral channels (better presentation) 2.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

Methods for Data analysis 1.Spectral analysis; 2.Time-frequency analysis – Wavelet; 3.Complex demodulation ( Draganova et al., 1999 ); 4.Steady-State responses (SSR) representation rate (Periodicity analysis, R.Draganova, 1998); 5.SAM analysis 6.Transient responses (P1-N1-P2; SSF) 7.Source Analysis

8 sec16 sec24 sec 32 sec0 sec 14 sec - TB14 sec baseline ScanScan ScanScan 4 sec BOLD response Stimuli blocks Silent fMRI Paradigm

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

Thank you for the attention !

Isochronous Stream