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Biomedical subjects

S Kiritani

Publications and source records attributed to S Kiritani.

At least 19 recordsLinked to original sources
PubMed2001

Elicitation of N400m in sentence comprehension due to lexical prosody incongruity.

The role of lexical prosody in the semantic integration of spoken sentences consisting of a quiz stem and an answer word was investigated analyzing the event-related magnetic response, N400m. Three conditions regarding the relations between the quiz and the answer word were prepared: pitch-accent violation, phonemic violation and no violation. Both the pitch-accent and phonemic violations elicited significant N400m without any significant differences in the peak latency and magnitude of the equivalent current dipoles, suggesting that the role of pitch-accent in semantic integration is equivalent to that of phonemes. However, the rate of violation detection and the successful N400m source estimation were lower for the pitch-accent violation than for the phonemic violation, suggesting differential neural processes for the phonemic and prosodic cues.

Adult↗
PubMed2001

Developmental change in auditory preferences for speech stimuli in Japanese infants.

The developmental change in auditory preferences for speech stimuli was investigated for Japanese infants aged 4-14 months old. We conducted three experiments using two speech pairs in the head-turn preference procedure. Infant-directed (ID) speech and adult-directed (AD) speech stimuli were used in a longitudinal study (Experiment 1) and a cross-sectional study (Experiment 2). Native (Japanese) and non-native (English) speech stimuli were used in a cross-sectional study (Experiment 3). In all experiments, infants demonstrated a developmental change in their listening preference. For the ID/AD speech pair used in Experiments 1 and 2, infants show a U-shaped developmental shift with three developmental stages: Stage 1, in which very young infants tend to prefer ID speech over AD speech; Stage 2, in which the preference for ID speech decreases temporarily; and Stage 3, in which older infants again show a consistent preference for ID speech. For the native/non-native speech pair, there is a tendency for an increased preference for native speech over non-native speech, although infants did not demonstrate a U-shaped pattern. The difference in developmental pattern between the two types of speech pairs was discussed.

Child Language↗
PubMed1999

Selective visual and auditory attention toward utterances-a PET study.

The purpose of this study was to reveal functional areas of the brain modulating processing of selective auditory or visual attention toward utterances. Regional cerebral blood flow was measured in six normal volunteers using positron emission tomography during two selective attention tasks and a control condition. The auditory task activated the auditory, inferior parietal, prefrontal, and anterior cingulate cortices. The visual task activated the visual association, inferior parietal, and prefrontal cortices. Both conditions activated the same area in the superior temporal sulcus. During the visual task, deactivation was observed in the auditory cortex. These results indicate that there exists a modality-dependent selective attention mechanism which activates or deactivates cortical areas in different ways.

Adolescent↗
PubMed1998

Task-dependent laterality for cue decoding during spoken language processing.

The task-dependent laterality of the auditory cortices was investigated by measuring the magnetic fields elicited by three forms of a Japanese verb, which differed in terms of prosodic and phonetic cues. Significant task-dependent magnetic fields were found in both hemispheres during a prosody-related task, but only in the left during a phoneme-related task. The latency was similar to the mismatch negatively which reflects the neural activity of automatic cue decoding. These results suggest that task-dependent schemata are activated at least partially in parallel with automatic cue-decoding processes such that those in the left hemisphere process linguistic information irrespective of acoustic cues whereas those in the right hemisphere process prosodic information.

Adult↗
PubMed1997

Vocal identification of speaker and emotion activates different brain regions.

Regional cerebral blood flow was measured in six healthy volunteers by positron emission tomography during identification of speaker and emotion from spoken words. The speaker identification task activated several audio-visual multimodal areas, particularly the temporal poles in both hemispheres, which may be involved in connecting vocal attributes with the visual representations of speakers. The emotion identification task activated regions in the cerebellum and the frontal lobe, suggesting a functional relationship between those regions involved in emotion. The results suggest that different anatomical structures contribute to the vocal identification of speaker and emotion.

Adolescent↗
PubMed1997

Effects and limitations of prosodic and semantic biases on syntactic disambiguation.

This paper examined the effects of prosody on the syntactic ambiguity resolution of Japanese sentences, especially with reference to the interaction with semantic bias. Syntactically ambiguous sentences with different types of semantic bias were constructed. The degree of bias in each sentence was evaluated through visual presentation experiments. Three types of sentences were selected based on the results of visual presentation experiments, were recorded with prosody maximally favoring each possible interpretation of the sentences, and were used as the stimuli for the auditory presentation experiments. The results showed that prosodic cues can influence the interpretation of a sentence even when the sentence is strongly semantically biased. The results also showed a limitation to prosodic cues. The prosodic biases alone were not sufficient to fully determine the interpretation of the sentences even when the sentences were neutrally biased semantically.

Humans↗
PubMed1997

Observation of neural processes of auditory scene analysis by magnetoencephalography.

In order to elucidate the auditory mechanism of sensory cue grouping and stream formation, we used a 37-channel SQUID magnetoencephalographic system to analyze the magnetic fields elicited by spoken sound stimuli consisting of an isolated word, an isolated consonant (/k/) burst, and a concurrent but perceptually segregated version of them. Only the overlapped /k/ burst among the five measured neural activities had a statistically significant difference in the location of the equivalent single-current dipoles in both hemispheres. The result suggests that the neurons activated by the overlapped /k/ burst are at least partially different from those activated by the other sounds: thereby supporting our new hypothesis that concurrent auditory events are spatially represented within the auditory cortex.

Adult↗
PubMed1982

Interaction between articulatory movements and vocal pitch control in Japanese word accent.

In order to investigate the interaction between articulatory and vocal pitch controls, EMGs of the cricothyroid (CT) and sternohyoid (SH) muscles were recorded during utterances of two-mora Japanese words with rising and falling accent types in the Tokyo dialects. The test words consisted of combinations of open and closed vowels. It was revealed that the changes in CT activity were consistently observed in correspondence with the F0 shift according to the accent types, while the SH muscle was observed to be active both for jaw opening and F0 lowering, with some subject-to-subject difference. It was also observed that the time lag between the decrease in CT activity and the F0 fall varied with a shift in the relative timing of SH activity in one subject, but not in the other. Articulatory jaw opening with SH activation was considered to positively contribute to F0 lowering, but the use of this mechanism appeared to be optional at least in the Tokyo accent.

Adult↗
PubMed1978

Analysis of abnormal articulatory dynamics in two dysarthric patients.

By means of pellet tracking techniques using an X-ray microbeam system, observations of the articulatory movements of various types of dysarthric subjects were conducted. In selected cases, electromyography (EMG) was also performed. The data were specifically examined for range, velocity, and consistency (reproducibility) of the movements of the articulators, as well as the pattern of coordination of the different articulators involved. It was found in the case of ataxic dysarthria of cerebellar origin, for example, that the dynamic patterns were best represented as a difficulty in the initiation of purposeful movements and an inconsistency of articulatory movements, particularly in the repetitive production of a monosyllable. On EMG, breakdown of the rhythmical patterns in the articulatory muscles was quite obvious in the repetition of a monosyllable. In the case of amyotrophic lateral sclerosis (ALS), decrease in the range and velocity of movements was noted. This resulted from reduced neuromuscular units (NMU) activities manifested in clinical EMG. Analysis of the dynamic aspects of the dysarthrias is a promising approach for elucidating the nature of central problems of speech production and for a differential diagnosis of various types of dysarthrias.

Action Potentials↗