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Biomedical subjects

S Kuriki

Publications and source records attributed to S Kuriki.

At least 19 recordsLinked to original sources
PubMed2004

Auditory evoked field responses in the left hemisphere to morphosyntactic violations in Korean sentence.

To investigate multiple cortical regions associated with syntactic processes at the sentence level, auditory evoked field responses to morphosyntactic violations were measured over the left hemisphere of seven subjects. Subjects were asked to judge the acceptability of the final verb in verb-ending Korean sentence. Measured field data were transformed to the fields that would be detected on a standard sensing plane and averaged across subjects in different violation conditions. In the grand average data, we found distinct features at latencies of 400 ms and 600 ms, which seem to be specific to morphosyntactic processes. Equivalent current dipoles (ECDs) plotted on a standard brain indicate the inferior frontal region and the superior temporal gyrus for 400 ms component, and the middle temporal gyrus for 600 ms component. Our MEG study localized the distinct cortical regions involved in syntactic processes, which may be reflected in LAN and P600 of ERP.

Acoustic Stimulation↗
PubMed2002

Localization accuracy of single current dipoles from tangential components of auditory evoked fields.

We investigated the localization accuracy of single current dipoles from the tangential components of auditory evoked fields. The tangential fields were measured using planar gradiometers arranged in a way so as to detect two orthogonal field components parallel to a flat plane. Field responses to 1 kHz pure tones were recorded and equivalent current dipoles (ECDs) of N1m peak were estimated based on a locally fitted spherical conductor model. As a measure of localization accuracy, the standard deviation of the coordinates of the ECDs of N1m was obtained from repeated measurements for one subject. The estimated ECDs had a standard deviation of 5.5 mm and their mean location was at the supratemporal plane in the sylvian fissure on the MR image of the subject. In order to investigate the contribution of various errors to the localization accuracy, simulations using a sphere model and experiments using a realistically shaped skull phantom were performed. It was found that the background noise, which consisted of instrumental noise and spontaneous brain fields, was the main source of the errors that could explain the observed standard deviation. Further, the amount of systematic error was much less than the standard deviation due to the background noise. These results suggest that the volume currents in a non-spherical conductor shape such as the temporal region do not produce substantial errors in the localization of current dipoles from tangential components of auditory evoked fields.

Acoustic Stimulation↗
PubMed2001

Enhanced late components of AEFs associated with the temporal lobe lesions.

We recorded auditory evoked magnetic fields (AEFs) by presenting pure tone bursts once every 4000 ms in 11 patients with a brain lesion in or in the vicinity of the auditory cortex. AEFs on the damaged side revealed several enhanced deflections in late-latency AEFs (slow AEFs), peaking at approximately 320 (DI), 1030 (D2) and 1600 (D3) ms post-stimulus in eight patients. All the dipoles of slow AEFs were concentrated in the superior temporal regions which were not involved by brain lesions. D1, D2 and D3 dipoles were uniformly upward, downward and upward, respectively. The dipole moment varied from 12 to 122 nAm and had no consistent relationship with latency. This is the first report describing slow AEFs in cases with temporal lobe lesions.

Auditory Cortex↗
PubMed2001

Reversible brain dysfunction in MELAS: MEG, and (1)H MRS analysis.

This case report describes a follow up investigation of a patient with impaired word discrimination due to mitochondrial encephalopathy with lactic acidosis and stroke-like syndrome (MELAS) using proton magnetic resonance spectroscopy ((1)H MRS) and auditory evoked magnetic fields (AEFs). The initial (1)H MRS showed no N-acetyl aspartate (NAA) and marked accumulation of lactate (Lac) in the stroke-like lesion of MELAS, which was silent in neural activity according to AEFs. The follow up investigations, however, demonstrated that NAA reappeared, that the formerly increased Lac signal was significantly reduced, and that the magnitude of AEFs of the lesion was markedly increased. Metabolic and functional changes in (1)H MRS and AEFs reflected the neurological recovery very well. The stroke-like lesion was shown, using AEFs and (1)H MRS, to be able to function properly, although brain tissue of the lesion initially had severe damage due to mitochondrial dysfunction.

Adult↗
PubMed2000

Auditory cortex responds in 100 ms to incongruity of melody.

In order to find the cortical neural activities that reflect musical processing, we conducted measurements of MEG responses while subjects listened to familiar melodies. Significant enlargement of the N1m peak was observed in the response to the endnote of a phrase that was deviated to out-of-key from the keynote. Equivalent current sources of the enlarged N1m response were localized in the cortical area of the superior temporal plane. These results suggest the possibility of fast neural processing, as early as 100 ms, of the auditory cortex detecting incongruity of a melody.

Adult↗
PubMed2000

Modulation of neural activities during visual processing in the human extrastriate visual cortex.

Magnetoencephalographic responses to single letters (Japanese monosyllabic characters) presented in the left visual field were measured during visual cognition tasks, in which subjects judged matching of characters in two different processes based on phonological and graphical cues. Equivalent current dipoles, which represent focal neural activities, were localized in the extrastriate visual cortex of the occipital to occipitotemporal regions. The main activities were observed in the right lateral area when the subjects detected shape, and also in the medial and inferior areas of both hemispheres when they detected rhyme. These results suggest that the neural activities in the extrastriate cortex, which are related to early processing of familiar visual forms, can be modified by the top-down control.

Adult↗
PubMed1999

Musicians with absolute pitch show distinct neural activities in the auditory cortex.

Meg responses from musicians who had absolute pitch and from non-musicians were measured while they received different auditory stimuli. The parameters of single equivalent current dipoles (ECDs) were calculated for the N1m responses occurring in the auditory cortex. The location of the ECD for the noise burst was significantly posterior to the ECDs for the tones in the two hemispheres of the musicians, but not for those of the non-musicians. Further, in the left hemisphere the ECDs for the musicians were significantly posterior to those for the non-musicians. These results suggest distinct neural activities in the auditory cortex of musicians, which may be the result of cortical plasticity produced by training and/or an inherent cortical structural specificity.

Acoustic Stimulation↗
PubMed1999

Motor planning center for speech articulation in the normal human brain.

In order to locate the coordination center of speech movements in the dominant hemisphere of the normal human brain, we measured magnetoencephalographic (MEG) signals from the left frontal area of right-handed subjects while they pronounced different words. A broad response appeared during a period of 120-320 ms before the onset of speech sound, and its current dipole sources were localized on the magnetic resonance images in a region around the superior end of the left insula. Further, the onset of the MEG response preceded by about 100 ms the perioral muscle activities that occurred for the articulation in speaking the words. These results suggest that the deep frontal region is involved in the articulatory programming of speech movements.

Adult↗
PubMed1999

Principal component elimination method for the improvement of S/N in evoked neuromagnetic field measurements.

In the study of magnetoencephalography, it is important to obtain evoked fields with good signal-to-noise ratios (S/N) and with a small number of epochs in averaging. The noises are considered to be mainly spontaneous neuromagnetic fields. In the present study, we propose a method to improve the S/N. The basic principle of this method is the elimination of a principal component (PC) of multichannel-recorded neuromagnetic fields, utilizing the synchronized characteristics of spontaneous rhythmic activities dominating the fields. The proposed method is, therefore, called the principal component elimination method (PCEM). PCEM was applied to neuromagnetic fields measured by a 37-channel superconducting quantum interference device system, on which computer-generated evoked fields were superposed, in order to examine possible improvement in S/N. It was found that elimination of the first PC could improve the S/N of the evoked fields. The improvement in S/N with elimination of the first PC, compared to conventional simple averaging, increased with increases in the number of epochs and reached more than 50% after averaging over 128 epochs. PCEM also reduced the number of epochs needed in averaging to about half of that needed in conventional simple averaging.

Adult↗
PubMed1998

Neural processing of words in the human extrastriate visual cortex.

Measurements of neuromagnetic fields were made for the responses to visually presented words comprised of Japanese characters (phonograms), and for comparison of responses to single characters and character symbols, while subjects performed, respectively, semantic category matching, rhyming, and character matching tasks. The magnetic field responses recorded from the occipital and occipitotemporal regions consisted of 2-3 major peak components, occurring between 150 and 300 ms after the onset of the visual forms. The localization of equivalent current dipole sources of these components within the brain structure of individual subjects indicated that the main regions of the neural activity occurring at 150-250 ms were located in the extrastriate visual cortices. They included the lateral area mostly at the occipital gyrus, medial area consisting of parieto-occipital and calcarine sulci and lingual gyrus, and ventral area which is continuous from the lingual gyrus (LG) to fusiform gyrus (FG). In the ventral LG/FG area the left side was activated primarily by words, while the right side was responsive in more or less equally to words, characters, and symbols. It is suggested that the left occipitotemporal LG/FG mediates the neural function that subserves the specific visual word processing and/or general analysis of complex graphical features of visual forms.

Adult↗
PubMed1997

Elevated plasma levels of interleukin-1 receptor antagonist and interleukin-10 in patients with acute myocardial infarction.

The study was undertaken to measure plasma interleukin-1 (IL-1) receptor antagonist and IL-10 concentrations in patients with acute myocardial infarction and to analyze their relationship to the hemodynamics, severity, and prognosis of myocardial infarction in its acute stages. We attempted to define the kinetics of IL-1 receptor antagonist and IL-10 in patients with acute myocardial infarction (n = 34, age 42-91 years, mean 68 years). Plasma IL-1 receptor antagonist and IL-10 levels were measured by enzyme-linked immunosorbent assay. Patients in group A (n = 17) had uncomplicated acute myocardial infarction (Killip class I). Patients in group B (n = 17) had severe acute myocardial infarction (Killip class II, III, or IV). Peak Il-1 receptor antagonist and IL-10 levels in group B were significantly higher (p < 0.05) than those of group A. In group B, the peak IL-1 receptor antagonist levels were significantly correlated with white blood cell counts (r = 0.63, p = 0.006), pulmonary capillary wedge pressure (r = 0.78, p = 0.0002), and cardiac index (r = -0.51, p = 0.04). Peak IL-10 levels were significantly correlated with white blood cell counts (r = 0.60, p = 0.01), the pulmonary wedge pressure (r = 0.73, p = 0.0008), and cardiac index (r = -0.50, p = 0.04). Moreover, a significant correlation was found between the peak IL-1 receptor antagonist and IL-10 levels (r = 0.91, p < 0.0001). The peak IL-1 receptor antagonist levels in nonsurvivors (n = 13) were significantly higher (p < 0.01) than those in survivors (n = 21). The plasma IL-1 receptor antagonist and IL-10 levels were closely correlated with the severity of hemodynamics in acute myocardial infarction and with the clinical status of patients with severe acute myocardial infarction. Results suggest that plasma IL-1 receptor antagonist and IL-10 can serve as prognostic indicators in cases of sever acute myocardial infarction.

Adult↗
PubMed1996

Magnetoencephalographic study on the cerebral neural activities related to the processing of visually presented characters.

Neuromagnetic fields were recorded from normal subjects to study the time course of cerebral neural activation while they performed a matching task of visual stimuli in which sequentially presented Japanese characters or unreadable pseudo-characters were compared according to phonological (reading of the characters) or graphical (geometry of the pseudo-characters) identity. In response to the single real-character or pseudo-character which was presented the latest distinct magnetic field components were observed, from which current dipole sources of the fields were localized in the individual magnetic resonance images of the brain. In the phonological identification, the sources were found in the parieto-occipital extrastriate cortex at 155-210 ms following the character presentation, and in the posterior temporal region (part of the Wernicke's area) and the posterior superior temporal region of the visual/auditory association cortex at 210-410 ms. The activity in these temporal regions was left hemisphere dominant, and may be the neural basis of phonological processing of the visual characters. In the graphical identification, sources occurring at 125-250 ms were noted in the inferior temporo-occipital region, and those at 180-460 ms in the posterior temporal and posterior superior temporal regions of the right hemisphere. These results indicate that the activities in the temporal area are lateralized to the left for the phonological processing and to the right for the graphical processing.

Adult↗
PubMed1996

Difference of EEG spectral powers observed between binocular rivalry and binocular fusion.

Spontaneous EEGs were measured at 12 electrode positions over the entire head when subjects perceived alternately one of two stimuli, that were given separately to the left and right eyes, in binocular rivalry. Upward and downward triangles of the same size were used as the two stimuli. The EEGs when subjects perceived a fused image in binocular fusion by receiving the same stimuli, i.e. upward or downward triangles, to the left and right eyes, under the same experimental conditions to binocular rivalry, were also measured for comparison. The difference of the EEG spectral powers obtained under the two states of binocular rivalry and binocular fusion was analyzed in the theta (4-7 Hz), alpha (8-13 Hz) and beta (16-24 Hz) bands. A significant difference in the power was obtained in the alpha band, although the physical parameters of the stimuli, i.e. the shape, luminance, size and contrast, given to both eyes in the states of rivalry and fusion were identical. A large difference of the alpha power was observed at the occipital, parietal and posterior temporal regions.

Adolescent↗
PubMed1996

Scalp distribution of the attenuated EEG rhythmic activities for dissimilar and/or moving images in binocular vision.

Spontaneous EEGs, at 16 electrode positions over the entire head in five healthy subjects, were measured and analyzed while the subjects gazed at a variety of images in binocular vision. A significant difference in the EEG alpha rhythm (8-13 Hz) was observed between the two states of gazing at stationary and moving gratings in binocular fusion (BF). The variation was large at the parietal and right posterior temporal regions. We also confirmed a significant difference of the alpha rhythm between binocular rivalry (BR) and BF, which was reported in our previous paper, using different images. A large variation between BR and BF was observed at the occipital, parietal and posterior temporal regions when a pair of stationary diagonal gratings was used. On the other hand, the variation was large at the parietal region when a pair of moving diagonal gratings was used. We may conclude from these results that neurophysiological activities in the vicinity of the parietal region are mainly involved in BR. On the other hand, neurophysiological activities in the occipital and posterior temporal regions may be involved not only in BR, but also in the processing of the movement. In the beta band (16-24 Hz), a large variation was observed at the parietal and central regions in all cases described above.

Alpha Rhythm↗
PubMed1995

Source analysis of magnetic field responses from the human auditory cortex elicited by short speech sounds.

We made a detailed source analysis of the magnetic field responses that were elicited in the human brain by different monosyllabic speech sounds, including vowel, plosive, fricative, and nasal speech. Recordings of the magnetic field responses from a lateral area of the left hemisphere of human subjects were made using a multichannel SQUID magnetometer, having 37 field-sensing coils. A single source of the equivalent current dipole of the field was estimated from the spatial distribution of the evoked responses. The estimated sources of an N1m wave occurring at about 100 ms after the stimulus onset of different monosyllables were located close to each other within a 10-mm-sided cube in the three-dimensional space of the brain. Those sources registered on the magnetic resonance images indicated a restricted area in the auditory cortex, including Heschl's gyri in the superior temporal plane. In the spatiotemporal domain the sources exhibited apparent movements, among which anterior shift with latency increase on the anteroposterior axis and inferior shift on the inferosuperior axis were common in the responses to all monosyllables. However, selective movements that depended on the type of consonants were observed on the mediolateral axis; the sources of plosive and fricative responses shifted laterally with latency increase, but the source of the vowel response shifted medially. These spatiotemporal movements of the sources are discussed in terms of dynamic excitation of the cortical neurons in multiple areas of the human auditory cortex.

Acoustic Stimulation↗