Biomedical subjects

Masato Yumoto

Publications and source records attributed to Masato Yumoto.

At least 19 recordsLinked to original sources

PubMed2006

A magnetoencephalographic study of Japanese vowel processing.

Magnetic brain responses were recorded to clarify the cortical representation of vowel processing in Japanese. We investigated the peak latencies and equivalent current dipoles of the auditory N1m responses to the Japanese vowels [a], [i], [o], and [u]. In intraindividual analyses for a single participant, well-replicated results for the dipole parameters supported the existence of phoneme-specific cortical maps for vowels. In the interindividual analyses for the eight participants, [a] and [i] elicited significantly earlier N1m responses than [u], and the dipole for [i] was more posteriorly oriented than [a] in the left hemisphere. The results of the current study suggest left hemispheric predominance in vowel processing and that factors associated with a different language system may modify the cortical map.

Acoustic Stimulation↗

PubMed2006

Neuromagnetic responses to binaural beat in human cerebral cortex.

The dichotic presentation of two sinusoids with a slight difference in frequency elicits subjective fluctuations called binaural beat (BB). BBs provide a classic example of binaural interaction considered to result from neural interaction in the central auditory pathway that receives input from both ears. To explore the cortical representation of the fluctuation of BB, we recorded magnetic fields evoked by slow BB of 4.00 or 6.66 Hz in nine normal subjects. The fields showed small amplitudes; however, they were strong enough to be distinguished from the noise accompanying the recordings. Spectral analyses of the magnetic fields recorded on single channels revealed that the responses evoked by BBs contained a specific spectral component of BB frequency, and the magnetic fields were confirmed to represent an auditory steady-state response (ASSR) to BB. The analyses of spatial distribution of BB-synchronized responses and minimum-norm current estimates revealed multiple BB ASSR sources in the parietal and frontal cortices in addition to the temporal areas, including auditory cortices. The phase of synchronized waveforms showed great variability, suggesting that BB ASSR does not represent changing interaural phase differences (IPD) per se, but instead it reflects a higher-order cognitive process corresponding to subjective fluctuations of BB. Our findings confirm that the activity of the human cerebral cortex can be synchronized with slow BB by using information on the IPD.

Acoustic Stimulation↗

PubMed2006

Comparison between mismatch negativity amplitude and magnetic mismatch field strength in normal adults.

The auditory mismatch negativity (MMN) or its magnetic counterpart (magnetic mismatch field, MMF) has been widely used to assess the ability of stimulus-driven change detection process in humans. The authors evaluated the similarity of inter-individual variation of the response strength between MMN and MMF recordings. Three types of MMN or MMF were recorded in ten healthy subjects: change in duration of pure-tone stimuli, change in duration of the Japanese vowel /a/, and difference between the Japanese vowels /a/ and /o/. There was no significant correlation between MMN amplitude and MMF strength under any condition and in either hemisphere. These results suggest that widely used indices of MMN in the two technologies, i.e., EEG-amplitude and MEG-ECD may not be proportional in an individual. To further clarify the differential significance of recording MMN/MMF may be important to establish MMN/MMF as clinical indices of individual ability of preattentive stage of auditory processing.

Adult↗

PubMed2005

Increased right auditory cortex activity in absolute pitch possessors.

We recorded the auditory-evoked magnetic fields from children and adults with absolute pitch during the following tasks: (1) hearing 1000 Hz pure tones inattentively, (2) hearing eight random tones inattentively and (3) listening to eight random tones and identifying each tone. In children with absolute pitch, there was no significant positive correlation between the appearance rate of N100m and the kinds of tasks. In adults with absolute pitch, only the right N100m dipole moments increased significantly in tasks (1) and (2). The present results suggest that the circuit for labeling in the right auditory cortex may lose a function from childhood to adulthood, which reveals neuroplasticity in the development of absolute pitch ability.

Acoustic Stimulation↗

PubMed2005

Auditory imagery mismatch negativity elicited in musicians.

A mismatch between auditory sensation and expectant imagery of syllables elicited a possible equivalent of mismatch negativity in a previous study. The purpose of this study was to verify whether auditory imagery from musical notation could also mediate such imagery-based mismatch negativity. Neuromagnetic recording was obtained from eight musicians, who were instructed to identify unpredictably occurring pitch mismatches between a random tone sequence and a visually presented musical score. The difference between incongruent and congruent responses showed a magnetic distribution consistent with two frontal-negative current dipoles bilaterally located in the vicinity of Heschl's gyrus, peaking at approximately 150 ms in latency. This imagery-based mismatch negativity may represent an early neural process of deviance detection between the sensory input and expectant imagery.

Acoustic Stimulation↗

PubMed2005

Audiovisual phonological mismatch produces early negativity in auditory cortex.

During silent reading, visual information provided by letters is converted to auditory information in the mind. The purpose of this study was to identify the primary locus for auditory verbal imagery in the brain. Neuromagnetic recording was obtained from 10 right-handed study participants, who were instructed to identify infrequently occurring phonological mismatches between a random-ordered sequence of syllable sounds and a visually presented syllabogram sequence. The activity difference in early latency, calculated by subtracting the averaged responses to matched syllables from the averaged responses to mismatched syllables, showed a spatiotemporal profile strikingly similar to that of mismatch negativity. Auditory imagery of forthcoming verbal sounds may establish a memory trace as a template for imagery-based mismatch negativity generation in the auditory cortex.

Acoustic Stimulation↗

PubMed2005

A modified parallel paradigm for clinical evaluation of auditory echoic memory.

We established a new parallel paradigm for mismatch negativity by presenting repetitive trains of three consonant-vowel syllables and those of three sinusoidal tones alternately. Magnetoencephalography was performed to test the new method, and mismatch negativities in six study participants with normal hearing were compared with the results of the conventional oddball paradigm. Peak amplitude and latencies of mismatch negativity showed no significant difference between the methods. The maximum amplitude in short memory probe interval of 1.0 s was significantly larger than in long memory probe interval of 3.0 s, demonstrating decay in auditory echoic memory caused by a prolonged memory probe interval. The new method facilitated simultaneous evaluation of mismatch negativity with various stimuli in a shorter period.

Acoustic Stimulation↗

PubMed2005

Perceptual categorization of sound spectral envelopes reflected in auditory-evoked N1m.

Magnetic responses to periodic complex sounds with equivalent acoustic parameters except for two different fundamental frequencies (F0) and 12 different spectral envelopes of vocal, instrumental, and linear shapes were recorded to determine the cortical representation of timbre categorization in humans. Responses at approximately 100 ms (N1m) to vocal and instrumental (nonlinear) sounds were localized significantly anterior to linear sound responses. N1m source strength for nonlinear sounds was significantly larger than that for linear sounds, and this difference was more marked in the left hemisphere than in the right. N1m peak latency only for vocal sounds was not affected by F0. Perceptual categorization was reflected in N1m source strength and location (linear or nonlinear), and in N1m latency (vocal or nonvocal).

Acoustic Stimulation↗

PubMed2005

Propofol attenuates oxidant-induced acute lung injury in an isolated perfused rabbit-lung model.

PURPOSE: Reactive oxygen species have been strongly implicated in the pathogenesis of acute lung injury (ALI). Some animal studies suggest that free radical scavengers inhibit the onset of oxidant-induced ALI. Propofol (2,6-diisopropylphenol) is chemically similar to phenol-based free radical scavengers such as the endogenous antioxidant vitamin E. Both in vivo and in vitro studies have suggested that propofol has antioxidant potential. We hypothesized that propofol may attenuate ALI by acting as a free-radical scavenger. METHODS: We investigated the effects of propofol on oxidant-induced ALI induced by purine and xanthine oxidase (XO), in isolated perfused rabbit lung, in two series of experiments. In series 1, we examined the relationship between the severity of ALI and the presence of hydrogen peroxide (H2O2). In series 2, we evaluated the effects of propofol on attenuating ALI and the dose dependence of these effects. The lungs were perfused for 90 min, and we evaluated the effects on the severity of ALI by monitoring the pulmonary capillary filtration coefficient (Kfc), pulmonary arterial pressure (Ppa), and the pulmonary capillary hydrostatic pressure (Ppc). RESULTS: In series 1, treatment with catalase (an H2O2 scavenger) prior to the addition of purine and XO resulted in complete prevention of ALI, suggesting that H2O2 may be involved closely in the pathogenesis of ALI. In series 2, pretreatment with propofol at concentrations in excess of 0.5 mM significantly inhibited the increases in the Kfc values, and that in excess of 0.75 mM significantly inhibited the increase in the Ppa values. CONCLUSION: Propofol attenuates oxidant-induced ALI in an isolated perfused rabbit lung model, probably due to its antioxidant action.

Animals↗

PubMed2005

Delayed automatic detection of change in speech sounds in adults with autism: a magnetoencephalographic study.

OBJECTIVE: Autism is a form of pervasive developmental disorder in which dysfunction in interpersonal relationships and communication is fundamental. This study evaluated neurophysiological abnormalities at the basic level of language processing, i.e. automatic change detection of speech and non-speech sounds, using magnetoencephalographic recording of mismatch response elicited by change in vowels and tones. METHODS: The auditory magnetic mismatch field (MMF) was evaluated in 9 adults with autism and 19 control subjects using whole-head magnetoencephalography. The MMF in response to the duration change of a pure tone or vowel /a/ and that in response to across-phoneme change between vowels /a/ and /o/, were recorded. RESULTS: The groups were not significantly different in MMF power under any conditions. However, the autism group showed a left-biased latency prolongation of the MMF particularly under the across-phoneme change condition, and this latency delay was significantly associated with greater symptom severity. CONCLUSIONS: These results suggest that adults with autism are associated with delayed processing for automatic change detection of speech sounds. These electrophysiological abnormalities at the earliest level of information processing may contribute to the basis for language deficits observed in autism. SIGNIFICANCE: These results provide the first evidence for delayed latency of phonetic MMF in adults with autism.

Acoustic Stimulation↗

PubMed2004

Interhemispheric transmission of visuomotor information for motor implementation.

Using transcranial magnetic stimulation (TMS), we addressed the contribution of both hemispheres to the visuomotor control of each hand. The subjects had to press one of two buttons as quickly as possible after the go-signal. A precue preceding this conveyed full, partial or no advance information (hand and/or button), such that reaction time (RT) shortened with increasing amount of information. We gave TMS over each hemisphere at various time intervals (100-350 ms) after the go-signal and before the expected onset of response, and measured its effect on RT, movement time (MT) and error rate. At short intervals (100-200 ms), left hemisphere TMS delayed RT and prolonged MT of both hands, while right hemisphere TMS delayed RT only of the right hand, without affecting error rates. At long intervals (250-350 ms), TMS produced slightly more pronounced RT delays of the contralateral hand. RT was delayed more if the precues were less informative. The results suggest the importance of interhemispheric transmission of visuomotor information for motor implementation. The right hemisphere may play a role mainly in calculating target and effector information, determining RT, while the left hemisphere may play a role in elaborating the motor program and determining MT.

Adult↗

PubMed2004

N100m in adults possessing absolute pitch.

We recorded the auditory evoked magnetic fields from adults with and without absolute pitch under the following conditions: hearing 1000 Hz pure tones inattentively (single tone session) and listening to eight random tones and identifying each tone (labeling session). In the adults with absolute pitch, the bilateral N100m dipole moments increased significantly in the labeling session. While, in the adults without absolute pitch, the left N100m dipole moment alone increased in the labeling session. These results suggest that the adults with absolute pitch execute the labeling task in the bilateral auditory cortices with interhemispheric cooperation, which does not operate in the adults without absolute pitch.

Adult↗

PubMed2004

Children are sensitive to averted eyes at the earliest stage of gaze processing.

Event-related responses to a face with forward gaze or averted gaze (gaze task) and two equiluminous mosaic images (mosaic task) were recorded from healthy children aged 8-12 years and adults, using MEG and EEG. In children, a clear occipito-temporal magnetic field activity (P1m, around 140 ms) was observed bilaterally, and the right P1m amplitude was increased when viewing a face with averted gaze compared with that when viewing a face with forward gaze. This effect was not observed in adults. Furthermore, the source for the right P1m in children in the gaze task was mainly located around the putative human MT/V5 area. These data suggest that the early occipito-temporal brain response observed as the P1m is a gaze-sensitive component in children.

Adult↗

PubMed2004

Abnormal association between reduced magnetic mismatch field to speech sounds and smaller left planum temporale volume in schizophrenia.

Schizophrenia is associated with language-related dysfunction. A previous study [Schizophr. Res. 59 (2003c) 159] has shown that this abnormality is present at the level of automatic discrimination of change in speech sounds, as revealed by magnetoencephalographic recording of auditory mismatch field in response to across-category change in vowels. Here, we investigated the neuroanatomical substrate for this physiological abnormality. Thirteen patients with schizophrenia and 19 matched control subjects were examined using magnetoencephalography (MEG) and high-resolution magnetic resonance imaging (MRI) to evaluate both mismatch field strengths in response to change between vowel /a/ and /o/, and gray matter volumes of Heschl's gyrus (HG) and planum temporale (PT). The magnetic global field power of mismatch response to change in phonemes showed a bilateral reduction in patients with schizophrenia. The gray matter volume of left planum temporale, but not right planum temporale or bilateral Heschl's gyrus, was significantly smaller in patients with schizophrenia compared with that in control subjects. Furthermore, the phonetic mismatch strength in the left hemisphere was significantly correlated with left planum temporale gray matter volume in patients with schizophrenia only. These results suggest that structural abnormalities of the planum temporale may underlie the functional abnormalities of fundamental language-related processing in schizophrenia.

Adult↗

PubMed2004

Middle-latency auditory-evoked magnetic fields in patients with auditory cortex lesions.

OBJECTIVE: To demonstrate the influence of auditory cortex lesions on auditory middle-latency responses (AMLRs) and middle-latency auditory-evoked magnetic fields (MLAEFs) in humans. MATERIAL AND METHODS: A total of 15 normal subjects, 9 patients with left auditory cortex lesions and 1 patient with a right auditory cortex lesion were studied. MLAEFs were recorded from each hemisphere of the brain in a magnetically shielded room using a 37-channel SQUID gradiometer. Simultaneously, AMLRs were recorded from the scalp at the vertex, C3 and C4. Tone bursts were used as auditory stimuli. RESULTS: Pam responses of the MLAEF, which are typically evoked in the latency range of the Pa of the AMLR, and are localized at the auditory cortex as dipoles, were impaired or abolished over the left auditory cortex lesion in the patients with left-hemisphere lesions, but the Pa of the AMLR persisted. CONCLUSION: The main generator of the Pam in MLAEF was demonstrated to be the auditory cortex. The results also show that the Pa of the AMLR is evoked only partly from the auditory cortex.

Acoustic Stimulation↗

PubMed2003

N100m in children possessing absolute pitch.

We recorded the auditory evoked magnetic fields from children with and without absolute pitch under the following conditions: (a) hearing 1000 Hz pure tones inattentively, (b) hearing eight random tones inattentively and (c) listening to eight random tones and identifying each tone. We calculated the appearance rate of N100m as the ratio of the subjects who had N100m. There was a significant positive correlation between the appearance rate of N100m and age in both groups. There was also a significant positive correlation between the appearance rate of N100m and the kinds of the task only in children without absolute pitch. These results suggest that, in the children with absolute pitch, N100m was elicited equally in every session because of their automatically driven auditory attention. No significant correlation was found between the appearance rate of N100m and the possession of absolute pitch.

Acoustic Stimulation↗

PubMed2003

Neuromagnetic correlates of impaired automatic categorical perception of speech sounds in schizophrenia.

Schizophrenia is associated with dysfunction in language processing. At the earliest stage of language processing, dysfunction of categorical perception of speech sounds in schizophrenia has been demonstrated in a behavioral task. The aim of this study was to assess automatic categorical perception of speech sounds as reflected by event-related changes in magnetic field power in schizophrenia. Using a whole-head magnetoencephalographic recording, the magnetic counterpart of mismatch negativity (MMNm) elicited by a phonetic change was evaluated in 16 right-handed patients with chronic schizophrenia and in 19 age-, sex-, and parental socioeconomic status-matched normal control subjects. Three types of MMNm (MMNm in response to a duration decrement of pure-tone stimuli; a vowel within-category change [duration decrement of Japanese vowel /a/]; vowel across-category change [Japanese vowel /a/ versus /o/]) were recorded. While the schizophrenia group showed an overall reduction in magnetic field power of MMNm, a trend was found toward more distinct abnormalities under the condition of vowel across-category change than under that of duration decrement of a vowel or tone. The patient group did not show abnormal asymmetries of MMNm power under any of the conditions. This study provides physiological evidence for impaired categorical perception of speech sounds in the bilateral auditory cortex in schizophrenia. The language-related dysfunction in schizophrenic patients may be present at the early stage of auditory processing of relatively simple stimuli such as phonemes, and not just at stages involving higher order semantic processes.

Adult↗

PubMed2003

Stepping stone sampling for retrieving artifact-free electroencephalogram during functional magnetic resonance imaging.

Ballistocardiogram and imaging artifacts cause major interference with simultaneous electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) recording. In particular, the large amplitude of the imaging artifact precludes easy retrieval of EEG signals during fMRI scanning. Recording with 20,000-Hz digitization rate combined with 3000-Hz low-pass filter revealed the real waveform of the imaging artifact, in which it was elucidated that each artifact peak precisely corresponded to each gradient component and actually had differential waveforms of the original gradient pulses. Based on this finding, to retrieve EEG signal during fMRI acquisition, a blip-type echo planar sequence was modified so that EEG sampling might be performed at every 1000 micros (digitization rate 1000 Hz) exclusively in the period in which the artifact resided around the baseline level. This method, called "stepping stone sampling," substantially attenuated the amplitude of the imaging artifact. The remnant of the artifact was subtracted from the averaged artifact waveform. In human studies, alpha activity was successfully retrieved by inspection, and its attenuation/augmentation was observed during eyes open/closed periods. Fast Fourier transform analysis further revealed that even from DC up to 120 Hz, retrieved EEG data during scanning had very similar power distributions to the data retrieved during no scanning, implying the availability of the high-frequency band of the retrieved EEG signals, including even the gamma band.

Adult↗