Ntnen et al. (1997) Language-specific phoneme representations revealed by electric and magnetic brain responses. Presented by Viktor Kharlamov September 27, 2006 University of Ottawa 2 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. 3 Finnish vs. Estonian Similar sound inventories, but: Finnish - 8 vowels Estonian - 9 vowels The vowel // only occurs in Estonian 4 Finnish vs. Estonian Vowel inventories: 5 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/, // or /o/ when the phoneme sounded as a good one (i.e., prototypical in their language.) Estonians also had an // response button. 6 Results Both Finns and Estonians judged vowels common to both languages similarly, but: Estonians also had // which is a prototype phoneme in Estonian Finns could perceive // (theres a drop in goodness), but didnt consider it a good phoneme 7 Results Good phoneme responses (%) 8 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 (//, //) Mismatch paradigm: e e e e e e e e e e e e e e e Attention-independent change-detection process (reading a self-chosen text) 9 Results Standard stimuli elicited a P1-N1-P2 waveform Deviant stimuli showed MMN Larger MMN with greater F2 deviation, but: Finns: // (prototype in Finnish) elicited a larger MMN than // (non-prototype in Finnish), although // deviated acoustically less from /e/ than // Estonians: no drop in amplitude 10 Results (2) MMN Amplitude: Claim: existence of neural traces of language-specific phoneme representations 11 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 // response) (non-prototype in Finnish), although // deviated acoustically less from /e/ than // Larger MMNM in the left hemisphere for prototypical deviant stimuli 12 MEG Experiment (2): MMNM originated at the left auditory cortex MMNM strength (dipole moment) was considerably greater for the prototype deviant (//, a phoneme in Finnish) than for the non-prototype deviant // (not a phoneme in Finnish) Right-hemisphere responses were weak 13 MEG Experiment (3): 14 Discussion: Found cortical, language-dependent memory traces of speech sounds (Finns dont treat // as a phoneme as its 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 (1 st year of life) 15 Discussion (2): MMNM results indicate that the left auditory cortex is involved in phonemic discrimination Both left/right cortices are used in acoustic discrimination 16 The end!!! p.s. Elm on epvarmaa, sy jlkiruoka ensin.