Biomedical subjects

I Koshida

Publications and source records attributed to I Koshida.

4 recordsLinked to original sources

PubMed2001

Brain lateralization for mismatch response to across- and within-category change of vowels.

Differences in hemispheric predominance between across- and within-category change perception of vowels were assessed using a whole-head magnetoencephalography. The magnetic mismatch responses (MMNm) to pure-tone and vowel within-category changes were significantly predominant in the right hemisphere; on the other hand, vowel across-category MMNm did not differ in power between hemispheres. The results suggest that both hemispheres are symmetrically activated in the preattentive across-category change perception of vowels, while the within-category change of a vowel is analyzed as the change in physical features of the stimuli, thus predominantly activating the right hemisphere. Thus, the relative contribution of the left auditory cortex in the preattentive speech processing may occur only at the level of perception of the vowel across-category change.

Acoustic Stimulation↗

PubMed2001

A topographical study of ERP correlates of semantic and syntactic violations in the Japanese language using the multichannel EEG system.

Language processing was investigated using event-related potentials obtained using a multichannel (58-channel) EEG system, with regard to semantic dependency (i.e., selectional restriction between a verb and the arguments it takes: the SR type) and syntactic dependency between sentence-final particles and interrogative phrases (the WH-Q type) in Japanese. It was found that semantic violations elicited the conventional N400, which was distributed in the bilateral occipital and the right temporal regions, and that the syntactic violations elicited the P600 in a broad area, predominantly in the centroparietal regions. Scalp current density mappings suggested that the right temporal cortex plays a significant role in integrating pieces of contextual information, especially when it is difficult to integrate a word in the context of a sentence, and that the P600 was connected to the syntactic processes conceivably indexed by the left temporal current sink with a relatively early onset.

Adult↗

PubMed1999

Electrophysiological evidence for sequential activation of multiple brain regions during the auditory selective attention process in humans.

In an attempt to examine dynamic involvement of multiple brain regions in the auditory selective attention process, negative difference wave (Nd) generators were assessed using a high-resolution EEG system (128ch) and scalp current density (SCD) analysis. Ten normal volunteers participated in the study. Event-related potentials were recorded during a selective attention task. Sequential SCD mappings revealed that current sinks were located in the bilateral temporal regions at 160 ms subsequent to the onset of stimuli, shifting the dipole orientation more tangentially to the scalp at around 220 ms. Moreover, a current sink was demonstrated in the midfrontal region at around 320 ms. These findings confirm that different cortical regions are sequentially involved in the auditory selective attention process.

Adult↗

PubMed1999

Multiple generators in the auditory automatic discrimination process in humans.

To reveal the spatiotemporal characteristics of the auditory automatic discrimination process, mismatch negativity (MMN) generators were assessed with a high-resolution EEG system (128ch) and scalp current density (SCD) analysis. Ten normal volunteers participated in the study. Event-related potentials were recorded during a selective attention task. Sequential SCD mappings revealed that a current sink/source combination in the left temporal regions and a current sink in the right frontotemporal regions appeared around 200 msec irrespective of the ear of stimulation. Moreover, a parietal sink/source combination was demonstrated on the right hemisphere around 240 ms irrespective of the ear of stimulation. These findings demonstrate that the auditory automatic change detection process is, both spatially and temporally, a multiple-generated system.

Acoustic Stimulation↗