Mikio Kubota

Human neuronal encoding of English syntactic violations as revealed by both L1 and L2 speakers

Our previous study [M. Kubota, P. Ferrari, T.P.L. Roberts, Magnetoencephalography detection of early syntactic processes in humans: comparison between L1 speakers and L2 learners, Neurosci. Lett. 353 (2003) 107-110] showed that an early syntactic response was elicited in first language (L1) speakers for within-phrase, but not across-phrase violations, implying that there may exist a continuum of neuronal error gravity. Such an early component was not elicited by second-language (L2) learners. The current auditory study investigated whether two types of different syntactic violations regarding noun-phrase raising (NP-raising) and case-filter constructions would elicit a prominent early syntactic component in each hemisphere for both L1 and advanced L2 speakers of English. Neuromagnetic fields were recorded, using a dual 37-channel gradiometer system. A prominent component, peaking at approximately 150 ms post-onset, was observed in both hemispheres of two groups in response to NP-raising induced violations, but not case-filter violations. The findings imply that L1 and L2 speakers have similar neuronal mechanisms subserving syntactic processing of such violations.

Magnetic mismatch fields elicited by vowel duration and pitch changes in Japanese words in humans: comparison between native- and non-speakers of Japanese

Previous event-related brain potential research showed that mismatch negativity was elicited by phoneme contrasts in fluent second language (L2) learners, but not in non-speakers of L2. The present study tested whether the magnetic mismatch field (MMF) would be elicited in response to temporal and spectral changes in three Japanese synthesized words for both native- and non-speakers of Japanese. Magnetoencephalography responses were recorded with a dual 37-channel gradiometer. Unlike short-to-long vowel duration and falling-to-level pitch changes, long-to-short duration and level-to-falling pitch changes elicited a prominent MMF bilaterally for both groups, peaking at around 100 ms after change onset for duration and 200 ms for pitch. The MMF component is sensitive to vowel shortening rather than lengthening and to pitch falling rather than leveling. Automatic detection of changes in vowel shortening and pitch falling is a useful index of language-non-specific auditory memory traces.

Neuromagnetic auditory cortex responses to duration and pitch changes in tones: cross-linguistic comparisons of human subjects in directions of acoustic changes

Our recent magnetic mismatch field (MMF) study found that shortened-vowel duration changes and level-to-falling pitch changes in Japanese words elicited a prominent MMF in two hemispheres for both native and nonnative speakers (Inouchi, M., Kubota, M., Ferrari, P. and Roberts, T.P.L., Magnetic mismatch fields elicited by Japanese words: vowel duration and pitch by native and nonnative speakers, Poster presented at the 31st Annual Meeting of Society for Neuroscience, November 10-15, San Diego, CA, 2001). The current study investigated whether shortened duration changes and level-to-falling pitch changes in non-speech (tones) would elicit a more prominent MMF component than lengthened duration changes and falling-to-level pitch changes, respectively. Stimuli included three computer-synthesized tones with varying duration or frequency modulation: (1). short duration and level pitch; (2). long duration and level pitch; (3). long duration and falling pitch. Magnetoencephalography responses were recorded with a dual 37-channel gradiometer system. The results showed that the prominent MMF component was generated in long-to-short duration changes and level-to-falling pitch changes in each hemisphere for both Japanese and American subjects. The component peaked at around 100 ms after change onset for duration changes and 170 ms for pitch changes. The MMF component in tones, like in words, was particularly sensitive to duration shortening and pitch falling. In summary, changes in duration shortening and pitch falling are particularly salient cues for pre-attentive auditory change detection in each hemisphere.

Human auditory evoked mismatch field amplitudes vary as a function of vowel duration in healthy first-language speakers.

Previous auditory studies demonstrated that vowel shortening elicited a more prominent mismatch component than its lengthening in event-related potentials (ERP) and magnetoencephalography (MEG). Based on these findings, the current study investigated whether the magnetic mismatch field (MMF) component would be generated by vowel shortening of various degrees to determine a neuronal response threshold of pre-attentive deviation detection. Behavioral pre-test data revealed that while listening to Japanese short-duration (100%: reference), long-duration (180%), and other in-between duration-synthesized types, healthy native speakers of Japanese failed to clearly categorize 140-124% durations as either short or long words, while categorizing 108-116% durations as short words and 148-172% durations as long. Following these results, MEG responses were recorded with a whole-head 148-channel magnetometer, as subjects listened to 100% standard and five deviant durations (124, 132, 140, 148, 180%). MEG results showed that the above-32% duration decrements (180-->100%, 148-->100%) elicited a more prominent MMF than the others, the MMF amplitudes increasing linearly to the degree of duration deviance, and that neuronal responses correlated with behavioral word-categorization accuracy.

Neuromagnetic mismatch field (MMF) dependence on the auditory temporal integration window and the existence of categorical boundaries: Comparisons between dissyllabic words and their equivalent tones

Previous duration-related auditory mismatch response studies have tested vowels, words, and tones. Recently, the elicitation of strong neuromagnetic mismatch field (MMF) components in response to large (>32%) vowel-duration decrements was clearly observed within dissyllabic words. To date, however, the issues of whether this MMF duration-decrement effect also extends to duration increments, and to what degree these duration decrements and increments are attributed to their corresponding non-speech acoustic properties remainto be resolved. Accordingly, this magnetoencephalographic (MEG) study investigated whether prominent MMF components would be evoked by both duration decrements and increments for dissyllabic word stimuli as well as frequency-band matched tones in order to corroborate the relation between the MMF elicitation and the directions of duration changes in speech and non-speech. Further, the peak latency effectsdepending on stimulus types (words vs. tones) were examined. MEG responses were recorded with a whole-head 148-channel magnetometer, while subjects passively listened to the stimuli presented within an odd-ball paradigm for both shortened duration (180-->100%) and lengthened duration (100-->180%). Prominent MMF components were observed in the shortened and lengthened paradigms for the word stimuli, but only in the shortened paradigm for tones. The MMF peak latency results showed that the words ledtoearlier peak latencies than the tones. These findings suggest that duration lengthening as well as shortening in words produces a salient acoustic MMF response when the divergent point between the long and short durations fallswithin the temporal window ofauditory integration post sound onset (<200 ms), and that theearlier latency of the dissyllabic word stimuli over tones is due to a prominent syllable structure in words which is used to generate temporal categorical boundaries.

The elicitation of phonological and semantic neuromagnetic field components by non-words in human auditory sentence comprehension

The current research examined whether neuromagnetic field components relating to pre-lexical and semantic analysis would be evoked by non-word violations in Japanese auditory sentence comprehension. Stimuli contained semantically congruent short vowel-duration words, long vowel-duration non-words, and short-duration non-words with a deviant second syllable. Native speakers listened to sentences, while neuromagnetic fields were recorded with a twin 37-channel gradiometer system. The results in the 200-400 ms time window showed that at a peak latency of approximately 300 ms, vowel-lengthening and deviant-syllable violations produced larger magnetic fields than congruent words. In the 450-600 ms time range, the magnetic fields in response to deviant-syllable violations, but not vowel-lengthening violations, were larger than congruent words, with the peak latency at approximately 500 ms. The elicitations of M300 and M500 components in this study support the biphasic hypothesis where a pre-lexical phonological analysis stage precedes a post-lexical semantic integration stage in lexical recognition of a native language.