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 byViktor Kharlamov

September 27, 2006University of Ottawa

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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.

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Finnish vs. Estonian

Similar sound inventories, but:

Finnish - 8 vowels

Estonian - 9 vowels

The vowel /õ/ only occurs in Estonian

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Finnish vs. Estonian

Vowel inventories:

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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.

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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”

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Results Good phoneme responses (%)

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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)

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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

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Results (2)

MMN Amplitude:

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

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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

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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

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MEG Experiment (3):

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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)

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Discussion (2):

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

Both left/right cortices are used in acoustic discrimination

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The end!!!

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