Torsten Dau AG Medizinische Physik

Präsentation zum Thema: "Torsten Dau AG Medizinische Physik"—  Präsentation transkript:

1 Modelle der auditorischen Verarbeitung: Perzeption und evozierte Potenziale
Torsten Dau AG Medizinische Physik Carl von Ossietzky Universität Oldenburg Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials?

2 Informationsverarbeitendes System Gehör
Hören ist essenziell für Sprachentwicklung und Kommunikation! Schall Andere Sinnes- systeme Codierung Verarbeitung Integration Erfahrung Verhalten/ Antwort/Reaktion Herausforderungen: Verständnis der zugrundeliegenden Prozesse. Modellierung der “effektiven” Signalverarbeitung. Nutzung für technische Anwendungen.

3 Überblick  „peripher”  „zentral”
Aufbau des Hörsystems: Physiologie und Anatomie. Signalverarbeitung in der Cochlea. Codierung von Amplitudenmodulationen im Gehör. Konsequenzen für technische Anwendungen und klinische Diagnostik.  „peripher”  „zentral” Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials?

4 Das Ohr aus „medizinischer Sicht”

5 Die Cochlea Cochlea Steigbügel Helicotrema Amboß Hammer Trommelfell
Scala tympani Scala media Scala vestibuli Basilarmembran Trommelfell Hammer Amboß Steigbügel Cochlea Rundes Fenster Ovales Helicotrema Wanderwelle

6 Neuronale Stationen bis zum Cortex
Auditory Cortex Inferior Colliculus Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials?

7 Das Gehör aus „physikalischer Sicht”
Frequenz-Orts-Abbildung Einhüllenden-extraktion Dau et al. (1997) (J. Acoust. Soc. Am.) Dynamik-kompression Zeitliche Kontrastierung Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Modulationsfrequenz-Orts-Abbildung Auflösungsgrenze Verarbeitung “gehörgerecht”? 

8 Filterbandbreite beim Menschen indirekt messbar
Frequenz-Orts-Transformation in der Cochlea Cochlea wirkt wie akustisches Prisma Neuronale Aktivität f Schallsignal Gehirn „Cochleäre Filter” Bandpass-Filterbank  Filterbandbreite beim Menschen indirekt messbar Tone Auditory Filter Noise Power Frequency Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Maskierungs- experimente 

9 Cochleäre Transformation
Amplitudengang wurde oft untersucht: Fletcher (1940), Zwicker et al. (1957), Plomp (1964), Patterson (1974). Phasengang wurde bisher wenig untersucht: (i) Gehör galt als phaseninsensitiv (Helmholtz). (ii) “Power spectrum model” erklärt viele Phänomene. Gehör ist zwar sensitiv für relative Phasenlage zwischen spekralen Komponenten. Dennoch wurde lange angenommen, daß der Einfluß des Gehörs auf Stimulusphase vernachlässigbar ist. Phasenantwort psychoakustisch messbar? Absolute Phase  und Gruppenlaufzeit nicht erfassbar, aber Phasenkrümmung:

10 Tonkomplex-Maskierer
Sine phase (m0) Schroeder negative (m-) Schroeder positive (m+) Amplitude 200 2000 Frequency (Hz) m+ m_ Schroeder (1970): Fundamental Frequency (Hz) m+ m- m0 Masked Threshold (dB) 20 dB Kohlrausch und Sander (1995)  Energie-Detektor Modell versagt

11 Erklärungsansatz Schroeder-Maskierer haben konstante Sweeprate (konstante Phasen-Krümmung): BM Stimulus Hypothese: Schwellenminimum, falls: Zeit Amplitude BM- Filterung Amplitude Zeit (bei 1 kHz)

12 Schätzung der Phasenkrümmung als Funktion von CF
m-- Masker Variation der Sweeprate: C Value 40 50 60 70 -1 -0.5 0.5 1 125 Hz 250 Hz 500 Hz 1000 Hz m0- Masker  Signal threshold (dB SPL) m+- Masker (fs = 1000 Hz) C Value Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Signal: 125, 250, 500, 1000 Hz Maskierer: n1 = 0.4fs ; nmax = 1.6fs f0 = 0.1fs ; N = 13 Oxenham und Dau (2001) (J. Acoust. Soc. Am.)  keine Dispersion bei tiefen Frequenzen

13 Schätzung der Phasenkrümmung der auditorischen Filter
100 1000 8000 Signal frequency (Hz) Stimulus curvature (rad/Hz2) 0.01 0.1 1 10 100 1000 10000 Signal frequency (Hz) Mean of minima Fitted minima Kohlrausch Lentz and Leek Shera(guinea pig) Normalized phase curvature Oxenham und Dau (2001) (J. Acoust. Soc. Am.) Etwa konstante relative Skalierung für Abweichung von relativer Skalierung für Phasengang von Filtern existierender Modelle unrealistisch.

14 Korrelation zur Physiologie
Übertragung an festem Ort x0 (als Funktion der Frequenz =f/CF) Shera (2001)  Frequenz-Dispersion  Impulsantwort: upward chirp Zeit Time Amplitude t1 t2 Übertragung für feste Frequenz f (als Funktion des Ortes) Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? 250 Hz  Räumliche Dispersion: (Wanderwelle) 4 kHz x Basis Apex

15 Woher kommt die Wanderwelle?
- Direkte Konsequenz aus den mechanischen Eigenschaften der Basilarmembran im umgebenden Medium - Räumliche Änderung (“Gradient”) der Steifigkeit der Basilarmembran Mechanisches Ersatzschaltbild Elektrisches Ersatzschaltbild + - Apex Basis I U Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? - Egbert de Boer (1980) entwickelt “Transmission-Line” Modell der Basilarmembran und berechnet Wanderwellenausbreitung

16 Konsequenzen der cochleären Dispersion
für akustisch evozierte Potenziale Evozierte Potenziale = Summation von Reizantworten vieler Neurone, abgeleitet im „Fernfeld” an der Schädeloberfläche. Klassisches Click-evoziertes Potenzial Picton et al. (1974) Potenzialamplitude wesentlich abhängig von: Anzahl der angeregten Neurone Synchronisation der Entladungen Click kann nicht optimal sein!

17 Ausgleich der Laufzeitunterschiede
Clickreiz nicht optimal um hohe Synchronisation zu erreichen. Mit Hilfe des de Boer-Modells (“exponential model”) lässt sich „vorverzerrter” Stimulus berechnen, der die Laufzeitunterschiede ausgleicht. Chirp-Reiz Dau et al. (2000) (J. Acoust. Soc. Am.) Click Chirp Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Apex Basis Basis Apex

18 Click- und chirp-evozierte Potenziale
III V Dau et al. (2000) (J. Acoust. Soc. Am.) Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials?  In Cochlea erzielte „optimale” Synchronisation durch den Chirp führt auch zu erhöhter Synchronisation im Hirnstamm (Welle V).

19 Up- versus down-chirp Dau et al. (2000) Thank you Peter!
rising Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Zeit Frequenz Dau et al. (2000) (J. Acoust. Soc. Am.)

20 Modellierung von evozierten Potenzialen?
Generatoren? ? s (t) Welche Population generiert welchen Potenzialpeak? Wie ist die Beziehung zwischen Hirnstammantworten und cochleärer Vorverarbeitung?

21 Potenzialgenerierung
1) 3) Potential produced by kth population ui(t) = unitary response ri(t) = instantaneous discharge rate Number of cells in the population 4) 2) Potential produced by one cell in that population Compound instantaneous discharge rate

22 „Impulsantworten” der beteiligten Generatoren
“Unitary response” im Modell: drei einzelne Antworten, die die Generatoren für die Wellen I, III, V repräsentieren. Form der peaks basiert auf physiologischen Daten. Let’s have a look at the auditory pathway: DORSAL VIEW of brainstem, thalamus and a part of the cortex The nervus cochlearis (VIII) goes to the nucleus cochlearis. From there the auditory pathway goes through the olivaris superior, further on to the lemniscus lateralis, the colliculus inferior to the corpus geniculatum mediale. The signals are then projected through the radiatio acustica to the auditory cortex in the planum temporale. The ABR generators are mainly located inside the brainstem. The generators for the ABR wave V were assumed to be in the region from the LL to the IC, which I marked with a yellow line. Let’s have a closer look to the ABR! Annahmen im Modell: Form der “unitary response” unabhängig von CF. “Template” unabhängig vom Stimulus und Pegel.

23 Neuronale Erregungsfunktion
Nichtlineares AN Modell von Heinz et al. (2001): Heinz et al. (2001) For example to a typical click evoked ABR: It is shown on the right side of the slide. Plotted is the potential difference between the ipsilateral mastoid and the vertex against the time. You see six different measuerments with different click levels from 10 to 60 dB SL in 10-dB steps. At high levels: wave I, II, III, IV and V siehe Folie Problem: It is well known that despite the fact that the click has a broad spectrum, low frequencies do not contribute to the wave-V apmlitude. The next slide shows the human ear! Berechnet stimulusabhängige Feuerrate r(t) als Funktion von CF.

24 Generatoren der Potenzialpeaks
Wave V- Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Wave III Wave V+ Wave I

25 Modellierung von evozierten Potenzialen
Idee: Berechnung der summierten synchronisierten Neuronenaktivität, basierend auf realistischem Cochlea-Modell. Dau (2002) (J. Acoust. Soc. Am., subm.) Mittelohrfilterung BM Bandpassfiltering (mit Feedback) IHZ-Transduction AN-Model Heinz et al. (2001) Adaptation IHZ-AN Synapse Mittlere Feuerrate + Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Summierte neuronale Aktivität Faltung mit “Unitary Response” + Internes Rauschen Evoziertes Potenzial

26 Vergleich von Simulation und Messung
Click Chirp Model Data Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Dau (2002) (J. Acoust. Soc. Am., subm.)

27 Beispiel für komplexe Stimulation
Data Model Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Dau (2002) (J. Acoust. Soc. Am., subm.)

28 Interpretation/Anwendungen
Verständnis der Verarbeitung in der Cochlea fundamental für die Interpretation der (frühen) Potenzialmuster. Modellierung erlaubt Vorhersage für beliebige Reize bei beliebigen Pegeln:  Aussagen über Frequenzspezifizität von Antworten möglich. Aussagen für beliebigen angenommenen Hörverlust möglich. Antwort auf tieffrequente Töne (z.B. 300 Hz) repräsentiert Aktivität von Neuronen, die auf höhere Frequenzen (> 1.2 kHz) abgestimmt sind. Wichtiges Hilfsmittel im Bereich der klinischen Diagnostik! Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials?

29 Das Gehör aus „physikalischer Sicht”
Frequenz-Orts-Abbildung Einhüllenden-extraktion Dau et al. (1997) (J. Acoust. Soc. Am.) Dynamik-kompression Zeitliche Kontrastierung Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Modulationsfrequenz-Analyse Auflösungsgrenze

30 Signalverarbeitung hinter der Cochlea
Hören ist mehr als nur cochleäre Verarbeitung! Bisher „nur” Zerlegung in Frequenzbänder durch Cochlea und Umwandlung in neuronale Aktivitätsmuster im auditorischen Nerven. Wichtige Informationen sind auch in zeitlicher „Grobstruktur” enthalten: Sprache, Musik, Umweltgeräusche durch Modulationen gekennzeichnet. Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials?

31 Extraktion der Einhüllenden in den Haarzellen
Feinstruktur wird abgebildet Pickles (1988) Einhüllende wird abgebildet Out Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Modellierung: +  Einhüllende In f 1 kHz Gleichrichtung Tiefpass-Filterung

32 Modulationstransferfunktion
Wie wird die Einhüllende weiterverarbeitet? Wie überträgt das Gehör Modulationen? Wie empfindlich ist das Gehör für Modulationen? „Einfachstes” Experiment: Modulationsdetektion mit Rauschträger Viemeister (1979) f = 6000 Hz fgr = 64 Hz “leicht” “schwierig” Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials?  Tiefpass-Charakteristik („Trägheit“) des Gehörs

33 Einhüllenden-Detektor Modell (Viemeister, 1979)
fgr = 64 Hz predetection filtering halfwave rectification lowpass filtering decision device Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Problem: Modell „funktioniert” nur bei Breitbandrauschen!

34 Messdaten für verschiedene Bandbreiten
f = 3 Hz f = 30 Hz f = 300 Hz Zeit (s) Amplitude Tiefpass-Verhalten gilt nicht allgemein! m at threshold (dB)  Viemeister-Modell versagt m at threshold (dB)  Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Neues Erklärungs- konzept notwendig! m at threshold (dB) Modulation frequency Dau et al. (1997) (J. Acoust. Soc. Am.)

35  Modulationsmaskierung Psychoakustische Maskierungsmuster
Modulations-filterbank signal masker  Ewert und Dau (2000) (J. Acoust. Soc. Am.)  Konstante Güte Q der Filter Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Analogie: Cochleäre Verarbeitung „Zentrale” Verarbeitung Frequenz-Zerlegung  Modulationsfrequenz-Zerlegung Prinzip: Tonotopie  Prinzip: Periodotopie

36 Modulationsfilterbank-Modell
Dau et al. (1997) (J. Acoust. Soc. Am.) Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials?

37 Experiment und Simulation
Modell erlaubt Nachbildung für breitbandige („klassische”) und schmalbandige Signale. Tiefpass-Charakteristik durch logarithmische Skalierung:   3dB-Anstieg pro Oktave f = 3 Hz m at threshold (dB) f = 3 Hz f = 30 Hz f = 30 Hz m at threshold (dB) My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? f = 300 Hz f = 300 Hz m at threshold (dB) Dau et al. (1997a,b) (J. Acoust. Soc. Am.) Modulation frequency

38 Modulationsspektrum von Gauß-Rauschen
Reelles Signal: Analyt. Signal Hilbert-Transformation Hilbert Einhüllende: mit Mod.-Spektrum: Spektrum Mod.-Spektrum Gauß- Rauschen Lawson & Uhlen- beck (1950) Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Wiener-Chintchin Theorem:

39 Dau et al. (1999) (J. Acoust. Soc. Am.)
“Envelope power spectrum model” 30 300 f = 30 Hz f = 300 Hz f = 3 Hz Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Träger-Modulationsspektrum Modulationsfilter- Übertragungsfunktion Einhüllendenfrequenz Dau et al. (1999) (J. Acoust. Soc. Am.)

40 Physiologische Modulationsfilter
Hirnstamm: Langner und Schreiner (1988) Kortex: Schulze et al. (2002) Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Korrelation unklar: - Frequenzselektivität größer in physiologischen Ableitungen - Biologische Realisation der Periodizitätsanalyse?

41 Objektbildung

42 Auditorische Objektbildung
Beispiel: Interferenzen bei der Modulationswahrnehmung (MDI = Modulation detection interference) Yost et al. (1989) Signal Signal ohne Maskierer Interferenz (MDI) Maskierer Zeit Frequenz Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? „Interferenz-Effekt”: Modulationen beeinflussen sich gegenseitig Klassisches Frequenzgruppenkonzept versagt: Wechselwirkung über Frequenzgruppen hinweg

43 Unabhängige Verarbeitung in allen Frequenzgruppen
Original-Perzeptionsmodell Unabhängige Verarbeitung in allen Frequenzgruppen  keine Interferenz Modell unrealistisch  Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials?

44 Erweitertes Verarbeitungsmodell
Frequenzgruppen- übergreifende Integration durch gemeinsame Filterbank Modell realistisch?  Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Dau und Verhey (1999)

45 Auditorische Objektbildung
Interferenzen bei der Modulationswahrnehmung (MDI = Modulation detection interference) Signal ohne Maskierer Signal Klassisches MDI Signal Aufhebung von MDI Signal Frequenz Signal Signal Signal Frequenz Maskierer Maskierer Zeit Zeit Maskierer Zeit Maskierer Zeit Zeit Oxenham und Dau (JASA, 2001) Zeit Oxenham and Dau (2001c) J. Acoust. Soc. Am. Interferenzeffekte (MDI) gekoppelt mit auditorischer Objektbildung. Aufhebung der Interferenz durch „sequential streaming”. Modell: „Hart verdrahtete” Integration macht keinen Sinn.

46 Modellierung auditorischer Objektbildung
Prozesse bei frequenzgruppenübergreifender Interaktion sind komplex. Stärke der Interferenz in der Wahrnehmung abhängig von objekt-bildenden Parametern wie: Synchronizität, Harmonizität, Tonhöhe, Räumliche Position, ... „Top-down” Prozesse in der Modellierung notwendig (zusätzlich zu den bisher angenommenen „bottom-up” Prozessen). Modellierung schwierig, aber wichtig für Nachbildung in realistischer akustischer Umgebung. Steht noch am Anfang. Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials?

47 Technische Anwendungen von Gehörmodellen
Codiertes Signal Qualitäts- Maß Original- Signalqualitäts-Bewertung (z.B. Mobiltelefon, Hörgerät, ...) Modell Erkenner Signal Sprach- und Mustererkennung Coder Modell Signal Decoder Signalkodierung (z.B. MP3- Kodierung, Handy...) Hörgeräte Modell (NH) Modell (SH) Modifi- kation Signal Hörgeräte

48 Schlechtere Zeit-auflösung
Anwendungen der Modelle in klinischer Diagnostik? Evozierte Potenziale: Möglichkeiten und Grenzen eines „objektiven“ Nachweises von Schwerhörigkeit. Verständnis der Entstehungsmechanismen und Lokalisation der Generatoren. Neuronale Korrelate von kognitiven Leistungen? Perzeptionsmodell: Besseres Verständnis von Schwerhörigkeit. Sind die beobachteten Eigenschaften gekoppelt oder unabhängig? Erhöhte Schwellen Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Schlechtere Zeit-auflösung Recruitment ? Schlechtere Frequenzauflösung Gestörtes binaurales Hören

49 Zusammenfassung (I) Signalverarbeitung im Gehör: „Hierarchische“ Vorgehensweise (peripher  zentral). Neuronale Kodierungsprinzipien und „effektive“ Modellierung. „Cochleäre Transformation“: Schätzung des Phasengangs der peripheren Filter durch Detektions-experimente  kritischer Test für Cochlea-Modelle. Inhomogene mechanische Eigenschaften der Basilarmembran Ursache der räumlichen Dispersion  Wanderwelle. Ausgleich der cochleären Laufzeitunterschiede führt auf Chirpreiz.  Optimaler Reiz zur Auslösung von Hirnstammantworten. Thank you Peter! My talk is about Auditory Evoked Potentials, especially about the Auditory Brainstem Response and how stimuli could be optimized to get better responses. Since auditory evoked responses represent the whole auditory pathway they are a good tool to get information about ist processing. This knowledge is important for neurophysiological modelling. If you have any question during my talk: Please feel free to ask! What do we need to be able to measure auditory evoked potentials? Modulationsverarbeitung: Konzept der „Periodotopie“ zusätzlich zur Tonotopie. Modulationsfilterbank-Analyse in jedem Frequenzkanal erforderlich. Mehrdimensionale interne Repräsentation auf zentraler Verarbeitungsstufe.

50 Zusammenfassung (II) Auditorische Objektbildung:
Klassisches Konzept „unabhängiger Beobachtungen“ beschränkt. Interferenzeffekte in der Wahrnehmung (Beispiel MDI). Stärke der Interferenz abhängig von objektbildenden Parametern. Modellierung schwierig. Top-down Prozesse notwendig. Anwendungen: Objektive Qualitätbewertung, Sprach- und Mustererkennung, Signal-kodierung, digitale Hörgeräte. Klinische Diagnostik: Besseres Verständnis von Schwerhörigkeit. Neuronale Grundlagen einfacher kognitiver Leistungen?

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