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Näätänen et al. (1997) Language-specific phoneme representations revealed by electric and magnetic brain responses. Presented by Viktor Kharlamov September 27, 2006 University of Ottawa. Introduction. The study of: Selective listening and event-related brain potential

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Presented by viktor kharlamov september 27 2006 university of ottawa

Näätänen et al. (1997) Language-specific phoneme representations revealed by electric and magnetic brain responses.

Presented by

Viktor Kharlamov

September 27, 2006

University of Ottawa


Introduction

Introduction

  • The study of:

  • Selective listening and event-related brain potential

  • Language-dependent memory traces

  • Language-specific phoneme representations as revealed by electric and magnetic brain responses.


Finnish vs estonian

Finnish vs. Estonian

  • Similar sound inventories, but:

  • Finnish - 8 vowels

  • Estonian - 9 vowels

  • The vowel /õ/ only occurs in Estonian


Finnish vs estonian1

Finnish vs. Estonian

  • Vowel inventories:


Behavioral task

Behavioral task

  • “Good phoneme” judgements

  • Subject is presented with sets of phonemes that differ only in the second-formant frequency

  • Subject is asked to press /e/, /ö/ or /o/ when the phoneme sounded as a “good” one (i.e., prototypical in their language.) Estonians also had an /õ/ response button.


Results

Results

  • Both Finns and Estonians judged vowels common to both languages similarly, but:

  • Estonians also had /õ/ which is a prototype phoneme in Estonian

  • Finns could perceive /õ/ (there’s a drop in “goodness”), but didn’t consider it a “good phoneme”


Results1

Results

  • Good phoneme responses (%)


Eeg experiment

EEG Experiment

  • 13 Finnish and 11 Estonian subjects

  • Presented with /e/ as the standard stimuli; /e/ was randomly replaced by deviant stimuli that differed from the standard only in F2 (/ö/, /õ/)

  • Mismatch paradigm:

    e e e e ö e e õ e e e e õ e e e ö e e …

  • Attention-independent change-detection process (reading a self-chosen text)


Results2

Results

  • Standard stimuli elicited a P1-N1-P2 waveform

  • Deviant stimuli showed MMN

  • Larger MMN with greater F2 deviation, but:

  • Finns: /ö/ (prototype in Finnish) elicited a larger MMN than /õ/ (non-prototype in Finnish), although /ö/ deviated acoustically less from /e/ than /õ/

  • Estonians: no drop in amplitude


Results 2

Results (2)

  • MMN Amplitude:

  • Claim: existence of neural traces of language-specific phoneme representations


Meg experiment

MEG Experiment:

  • 9 Finnish subjects

  • Same experimental paradigm as the EEG experiment, but: measuring MMNM

  • Same pattern of response in the left hemisphere (the diminished /õ/ response) (non-prototype in Finnish), although /ö/ deviated acoustically less from /e/ than /õ/

  • Larger MMNM in the left hemisphere for prototypical deviant stimuli


Meg experiment 2

MEG Experiment (2):

  • MMNM originated at the left auditory cortex

  • MMNM strength (dipole moment) was considerably greater for the prototype deviant (/ö/, a phoneme in Finnish) than for the non-prototype deviant /õ/ (not a phoneme in Finnish)

  • Right-hemisphere responses were weak


Meg experiment 3

MEG Experiment (3):


Discussion

Discussion:

  • Found cortical, language-dependent memory traces of speech sounds (Finns don’t treat /õ/ as a phoneme as it’s not a prototype in Finnish)

  • The traces are activated only in the processing of speech and they act as recognition patterns

  • Recognition patterns develop gradually with exposure to language (1st year of life)


Discussion 2

Discussion (2):

  • MMNM results indicate that the left auditory cortex is involved in phonemic discrimination

  • Both left/right cortices are used in acoustic discrimination


Presented by viktor kharlamov september 27 2006 university of ottawa

The end!!!

p.s. Elämä on epävarmaa, syö jälkiruoka ensin.


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