Biomedical subjects

Atsuko Gunji

Publications and source records attributed to Atsuko Gunji.

10 recordsLinked to original sources

PubMed2006

Rhythmic brain activities related to singing in humans.

To investigate the motor control related to sound production, we studied cortical rhythmic changes during continuous vocalization such as singing. Magnetoencephalographic (MEG) responses were recorded while subjects spoke in the usual way (speaking), sang (singing), hummed (humming) and imagined (imagining) a popular song. The power of alpha (8-15 Hz), beta (15-30 Hz) and low-gamma (30-60 Hz) frequency bands was changed during and after vocalization (singing, speaking and humming). In the alpha band, the oscillatory changes for singing were most pronounced in the right premotor, bilateral sensorimotor, right secondary somatosensory and bilateral superior parietal areas. The beta oscillation for the singing was also confirmed in the premotor, primary and secondary sensorimotor and superior parietal areas in the left and right hemispheres where were partly activated even for imagined a song (imaging). These regions have been traditionally described as vocalization-related sites. The cortical rhythmic changes were distinct in the singing condition compared with the other vocalizing conditions (speaking and humming) and thus we considered that more concentrated control of the vocal tract, diaphragm and abdominal muscles is responsible. Furthermore, characteristic oscillation in the high-gamma (60-200 Hz) frequency band was found in Broca's area only in the imaging condition and might occur singing rehearsal and storage process in Broca's area.

Adult↗

PubMed2006

The magnetoencephalographic response to upright and inverted face stimuli in a patient with Williams syndrome.

The processing of faces in a patient with Williams syndrome was investigated using magnetoencephalography by evaluating responses to upright and inverted face stimuli. His processing of upright faces was not different from that of healthy adults. However, the processing of inverted faces was faster than those of healthy adults and faster than his processing of upright faces. The result indicated the absence of face inversion effect usually observed in healthy adults.

Adolescent↗

PubMed2005

Serial and parallel processing in the human auditory cortex: a magnetoencephalographic study.

Although anatomical, histochemical and electrophysiological findings in both animals and humans have suggested a parallel and serial mode of auditory processing, precise activation timings of each cortical area are not well known, especially in humans. We investigated the timing of arrival of signals to multiple cortical areas using magnetoencephalography in humans. Following click stimuli applied to the left ear, activations were found in six cortical areas in the right hemisphere: the posteromedial part of Heschl's gyrus (HG) corresponding to the primary auditory cortex (PAC), the anterolateral part of the HG region on or posterior to the transverse sulcus, the posterior parietal cortex (PPC), posterior and anterior parts of the superior temporal gyrus (STG), and the planum temporale (PT). The mean onset latencies of each cortical activity were 17.1, 21.2, 25.3, 26.2, 30.9 and 47.6 ms respectively. These results suggested a serial model of auditory processing along the medio-lateral axis of the supratemporal plane and, in addition, implied the existence of several parallel streams running postero-superiorly (from the PAC to the belt region and then to the posterior STG, PPC or PT) and anteriorly (PAC-belt-anterior STG).

Adult↗

PubMed2005

Time may be compressed in sound representation as replicated in sensory memory.

The flow of time in the real world may differ from the one in the neural representation of auditory scene stored in the sensory memory, because the encoded information is free from the rule of actual time. The sensory memory underlying the automatic discriminative system is reflected by the mismatch negativity (MMN). The time-wise image of preceding sounds is integrated into the sensory memory as a 160-170 ms epoch. We measured the mismatch field (MMNm) and the reaction time responding to the omitted segments incorporated into a complex sound. The main result was that the encoded period from early to late omitted segment was shorter than the actual one, suggesting that time may be compressed in the sound representation.

Acoustic Stimulation↗

PubMed2005

Effect of bilingualism on cognitive control in the Simon task: evidence from MEG.

The present study used magneto-encephalography (MEG) to determine the neural correlates of the bilingual advantage previously reported for behavioral measures in conflict tasks. Bilingual Cantonese-English, bilingual French-English, and monolingual English speakers, performed the Simon task in the MEG. Reaction times were faster for congruent than for incongruent trials, and the Cantonese group was faster than the other two groups, which did not differ from each other. Analyses of the MEG data using synthetic aperture magnetometry (SAM) and partial last squares (PLS) showed that the same pattern of activity, involving signal changes in left and medial prefrontal areas, characterized all three groups. Correlations between activated regions and reaction times, however, showed that the two bilingual groups demonstrated faster reaction times with greater activity in superior and middle temporal, cingulate, and superior and inferior frontal regions, largely in the left hemisphere. The monolinguals demonstrated faster reaction times with activation in middle frontal regions. The interpretation is that the management of two language systems led to systematic changes in frontal executive functions.

Adult↗

PubMed2003

Magnetoencephalographic study of the cortical activity elicited by human voice.

In an attempt to identify voice-specific neural activities in auditory cortex in humans, we recorded cortical magnetic responses. Volunteers were instructed to listen to vocal and instrumental sounds matched in fundamental-frequency, duration, temporal envelope and average root mean square power. The stimuli were sounds produced by four singers and four musical instruments at each of two fundamental frequencies: 220 Hz (musical note A3) and 261.9 Hz (C3). Two components of the evoked responses were analyzed, one at approximately 100 ms (N1m) and the other 400 ms after the stimulus onset (sustained field, SF). The source locations of equivalent current dipoles for both components were estimated around the Heschl's gyrus in both hemispheres. Compared with the instrumental sound, the source strength of the SF component for the voice was significantly larger.

Acoustic Stimulation↗

PubMed2003

Current source density distribution of sleep spindles in humans as found by synthetic aperture magnetometry.

Previous magnetoencephalography (MEG) studies of sleep spindles have identified a complex and widespread distribution in parietal and frontal cortices by fitting a dipolar model to the data. In this study, we used a whole-head 151-channel MEG system with simultaneous electroencephalography (EEG) recording in eight normal subjects. All subjects fell asleep during stage 2 and 3; EEG spindles have been observed in all cases. The current source density distribution of sleep spindles in the 10-15 Hz frequency band was localized by means of synthetic aperture magnetometry, and statistically tested using a permutation analysis. Source locations of the sleep spindles were found primarily in the frontal cortex, including dorsolateral and medial prefrontal areas, as well as the parietal cortex, including the vicinity of the primary sensorimotor areas. These results suggest that sleep spindles are similar in frequency content and spatial location to mu rhythm, and that these two oscillatory activities might also have a common neural basis and physiological meaning.

Adult↗

PubMed2003

Cortical activities relating to modulation of sound frequency: how to vocalize?

This is the first report to clarify the underlying mechanisms of processing in the modulation of frequencies (tones) in humans using magnetoencephalography (MEG). Volunteers were instructed to vocalize a simple vowel sound (/u/) after receiving a cue (S2) for either one of three (low, middle, or high fundamental frequencies) (F0s). Three tasks, (1) the modulated vocalization task in which the subjects were asked to modulate vocalization tones according to S2, (2) the non-modulated vocalization task in which the subjects were asked to vocalize the same sound (/u/) with a fixed F0, and (3) the image task in which the subjects had to modulate according to S2 and imagine the vowel (/u/) sound, but not vocalize it. In all tasks, two clear components, 1M and 2M, were recorded at approximately 190 and 290 ms after the S2. Since both were identified even in the Image task, they appear to be specifically related to activity for modulation. The equivalent current dipoles of both 1M and 2M were estimated to lie mainly in the inferior frontal lobe or insula in both hemispheres. Therefore, the activity relating to modulation mainly took place in the inferior frontal lobe or insula in both hemispheres starting about 200 ms after the viewing of a cue.

Acoustic Stimulation↗

PubMed2003

Cortical evidence of the perceptual backward masking effect on /l/ and /r/ sounds from a following vowel in Japanese speakers.

We examined the influence of stimulus duration of foreign consonant vowel stimuli on the MMNm (magnetic counter part of mismatch negativity). In Experiment 1, /ra/ and /la/ stimuli were synthesized and subjects were native Japanese speakers who are known to have difficulty discriminating the stimuli. "Short" duration stimuli were terminated in the middle of the consonant-to-vowel transition (110 ms). They were nevertheless clearly identifiable by English speakers. A clear MMNm was observed only for short-duration stimuli but not for untruncated long-duration (150-ms) stimuli. We suggest that the diminished MMNm for longer duration stimuli result from more effective masking by the longer vowel part. In Experiment 2 we examined this hypothesis by presenting only the third formant (F3) component of the original stimuli, since the acoustic difference between /la/ and /ra/ is most evident in the third formant, whereas F1 and F2 play a major role in vowel perception. If the MMNm effect depends on the acoustic property of F3, a stimulus duration effect comparable to that found with the original /la/ and /ra/ stimuli might be expected. However, if the effect is attributable to the masking effect from the vowel, no influence of stimulus duration would be expected, since neither stimulus contains F1 and F2 components. In fact, the results showed that the "F3 only" stimuli did not show a duration effect; MMNm was always elicited independent of stimulus duration. The MMN stimulus duration effect is thus suggested to come from the backward masking of foreign consonants by subsequent vowels.

Acoustic Stimulation↗

PubMedDate not supplied

Prospective clinical trial comparing lingualized occlusion to bilateral balanced occlusion in complete dentures: a pilot study.

PURPOSE: The aim of this prospective comparative trial was to evaluate whether patients treated with complete dentures with lingualized occlusion (LO) exhibited more positive results than patients treated with complete dentures with bilaterally balanced occlusion (BBO). MATERIALS AND METHODS: Twenty-eight completely edentulous patients, ranging in age from 60 to 82 years (mean age 70.9), consented in writing to be participants in this trial. The first 14 patients enrolled in the study protocol were treated with complete dentures with LO, and the next 14 patients were treated with complete dentures with BBO. Baseline characteristics were measured prior to the trial. Main outcome variables involved subjective outcomes of general satisfaction, ability to masticate, and stability and retention of the prostheses; these were quantified with a 100-mm visual analog scale. Objective outcomes were masticatory performance and the number of adjustments. Statistical assessments of the 2 groups were compared using multiple linear regression analysis. The baseline characteristics were analyzed by Student t test and chi-square test. RESULTS: There were no significant differences between the groups at baseline. The height of the alveolar ridge exhibited significant correlations with masticatory performance (P = .02). The occlusal scheme exhibited a significant correlation with only the patient's retention satisfaction rating (P = .03). CONCLUSION: Despite limitations of this study attributed to the small sample size and lack of randomization, this pilot study found that edentulous patients fitted with complete dentures with LO experienced and expressed greater satisfaction with their denture retention. In addition, it was observed that a higher alveolar ridge resulted in greater masticatory performance.

Aged↗