| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2005: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2004: ¥2,400,000 (Direct Cost: ¥2,400,000)
|
|---|
| Research Abstract |
Sounds with relatively long duration elicit a sustained component (Sustained Field, SF) following Nlm. The source of Nlm and SF were proximately located in the auditory cortex (Eulitz et al., 1995; Gunji et al., 2003). In the present study, we recorded cortical magnetic responses elicited by vowels and examined whether SF differs between native and non-native vowels. Eight native Japanese speakers participated (right handed). Four synthesized vowels and pure tones (500, 800, 1200and 2000Hz) were used as stimuli. Two of the vowels (/a/,/o/) are native for Japanese and the other vowels (/ae/, schwa) are not native. The duration of all the stimuli was 600ms (rise/fall, 20ms). Two inter-stimulus intervals (ISI) were used (short, 1200ms; long, 4800ms). Neuromagnetic responses were recorded using a 204-channel whole head system (Neuromag Inc, Helsinki). All stimulus elicited Nlm and SF. A significant effect of interval was found for Nlm to the vowels (both hemispheres) and to the tones (the
… More
right hemisphere). For the native vowels, early SF (250-300ms) was larger for the long than for the short interval session in both hemispheres. For the non-native vowels, early SF was larger for the long than the short interval session only in the right hemispheres. For the tones, no interval effect was found for early SF. Neither an effect of interval nor hemisphere was significant for later part of SF (400-600ms) regardless of stimulus types. In the present study, the ISI effect on Nlm differed between the vowels and the pure tones and that on the early SF latency range differed between the native and the non-native vowels only in the left hemisphere. This latency range might be related to elaborate phonetic processing. We also compared the auditory cortical response to musical chords and speech sounds and fond that the response after 200ms from stimulus onset differed between musical chords and speech sounds (Kuriki et al., 2007). Hence it is suggested that cortical activities 200ms after the stimulus onset are closely related to interaction between input sound and long term memory. Less
|
