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Biomedical subjects

M Miyatani

Publications and source records attributed to M Miyatani.

13 recordsLinked to original sources
PubMed2006

Compensatory cortical activation during performance of an attention task by patients with diffuse axonal injury: a functional magnetic resonance imaging study.

OBJECTIVE: To determine how cortical compensation occurs in higher cognitive systems during the recovery phase of diffuse axonal injury (DAI). DESIGN: 12 right-handed patients with a magnetic resonance imaging (MRI) lesion pattern compatible with pure DAI were identified. Pure DAI was defined as finding of traumatic microbleeds on T2*-weighted gradient-echo images in the absence of otherwise traumatic or non-traumatic MRI abnormalities. 12 matched healthy controls were also enrolled. Functional magnetic resonance imaging (fMRI) was used to assess brain activation during a working memory test (Paced Visual Serial Attention Test (PVSAT)). RESULTS: No significant group differences were observed in reaction times for the PVSAT. Although patients with pure DAI committed a few errors during the PVSAT, controls respond correctly to each probe. Controls showed activations in the left frontal gyrus, left parietal gyrus and right inferior parietal gyrus. Patients with pure DAI showed activations in the left inferior frontal gyrus, right inferior frontal gyrus and right middle frontal gyrus. Between-group analysis of the PVSAT task showed significantly greater activation of the right inferior frontal gyrus (BA 45) and right middle frontal gyrus (BA 9) in patient with pure DAI versus controls. CONCLUSIONS: Patients with pure DAI require compensatory activation of the contralateral (right) prefrontal region to carry out activities similar to healthy controls. These findings provide further evidence for the adaptive capacity of neuronal systems and brain plasticity during the recovery stages of DAI.

Adolescent↗
PubMed2003

Rehabilitation technique facilitates association cortices in hemiparetic patients: functional MRI study.

We used fMRI to study brain activation with facilitative rehabilitation techniques (passive hand movements and visual feedback) in two patients with subcortical lesions. Two tasks were given in a sequence. The first task (trial 1) was repetitive hand grasping by the paretic hand at a rate of 0.5 Hz with the eyes closed. The second task (trial 2), the facilitative rehabilitation technique, included task 1 plus support by a trainer to move the paretic hand with the eyes open to get visual feedback of the movement. The data were analyzed by a subtractive method. When task 1 was subtracted from task 2, it was found that the bilateral visual cortex, contralateral premotor cortex and posterior parietal cortex were involved with the passive hand movement and visual feedback. These facilitative rehabilitation techniques may integrate networks between sensory information and motor commands, and lead to functional reorganization.

Adult↗
PubMed2003

Effect of low-load resistance training on the tendon properties in middle-aged and elderly women.

AIM: The purposes of this study were to determine the age-related changes in the tendon-aponeurosis structures and to investigate the effects of low-load resistance training on the tendon-aponeurosis structures in middle-aged and elderly women. METHODS: Fifty-one women (55.8 +/- 13.7 years, range: 21-77 years) volunteered to take part in the present study. Furthermore, 11 middle-aged and elderly women (49.7 +/- 9.2 years) performed the low-load resistance training, i.e. squat using body weight, for 6 months. The elongation of the tendon and aponeurosis of the vastus lateralis muscle was directly measured by ultrasonography, while the subjects performed ramp isometric knee extension up to the voluntary maximum, followed by a ramp relaxation. The relationship between the estimated muscle force (Fm) and tendon elongation (L) during the ascending phase was fitted to a linear regression, the slope of which was defined as stiffness. The percentage of the area within the Fm-L loop to the area beneath the curve during the ascending phase was calculated as hysteresis. RESULTS: Maximal strain (L/initial tendon length) and stiffness of the tendon-aponeurosis structures decreased significantly with ageing. In contrast, the hysteresis increased significantly with ageing. In addition, low-load resistance training produced no significant change in stiffness and hysteresis, but significantly increased the maximal elongation of tendon-aponeurosis structures from 23.3 +/- 2.1 mm to 24.8 +/- 2.2 mm (P = 0.045). CONCLUSION: These results suggest that increasing age results in a decrease in the elasticity of tendon-aponeurosis structures and an increase in their viscosity. Furthermore, the low-load resistance training made the elasticity of tendon-aponeurosis structures increase.

Adult↗
PubMed2002

Pupal commitment and its hormonal control in wing imaginal discs.

The timing of pupal commitment of the forewing imaginal discs of the silkworm, Bombyx mori, was determined by a transplantation assay using fourth instar larvae. The wing discs were not pupally committed at the time of ecdysis to the fifth instar. Pupal commitment began shortly after the ecdysis and was completed in 14 h. When the discs of newly molted larvae (0-h discs) were cultured in medium containing no hormone, they were pupally committed in 26 h. In vitro exposure of 0-h discs to 20-hydroxyecdysone accelerated the progression of pupal commitment. Methoprene, a juvenile hormone analog (JHA), did not suppress the change in commitment in vitro at physiological concentrations. Thus the wing discs at the time of the molt have lost their sensitivity to JH, and 20E is not a prerequisite for completion of pupal commitment. These results suggest that the change in commitment in the forewing discs may begin before the last larval molt.

Journal Article↗
PubMed2001

Muscle volume is a major determinant of joint torque in humans.

Muscle force (MF) is linearly related to physiological cross-sectional area (CSA), which is obtained from muscle volume (MV) divided by fibre length. Taking into account the fact that joint torque (TQ) is determined by MF multiplied by the moment arm, the maximal TQ would be a function of MV. This proposition was tested in the present study by investigating the relationship between MV and TQ for elbow flexor (EF) and extensor (EE) muscles of 26 males. The MVs of EF and EE were determined from a series of muscle CSA by magnetic resonance imaging (MRI), and pennation angle (theta) and FL by ultrasonography (US). Maximal isometric TQ was measured at right angle of elbow joint for EF and EE. There was a highly significant correlation between MV and TQ both for EF and EE (r=0.95 and 0.96 respectively) compared with that between muscle CSA and TQ, suggesting the dependence of TQ on MV. Furthermore, prediction equations for MV (MVULT) from muscle thickness (MT) measured by US was developed with reference to MVMRI by the MRI on 26 subjects, and the equations were applied to estimate MV of healthy university students (CON; 160 males) and sports athletes (ATH; 99 males). There were significant linear relationships between MVULT and TQ both for EF (r=0.783) and EE (r=0.695) for all subjects (n=259). The MVULT was significantly higher in ATH (by 32% for EF and 33% for EE, respectively) than in CON. Similarly, significantly greater TQ was observed in ATH (by 35% for EF, 37% for EE, respectively). The theta for EE showed no difference between both groups (17.8 degrees for CON and 17.5 degrees for ATH). On the other hand, the TQ to MV ratio were identical for CON and ATH. The results reveal that the muscle volume of the upper arm is a major determinant of joint torque (TQ), regardless of athletic training.

Adult↗
PubMed2001

The effect of informative and uninformative cueing of attention on feature integration.

In the present study, the authors observed the effect of informative and uninformative attentional cueing on visual search for targets that were defined by a simple feature or by conjunctions of features. Three different types of attentional cueing were tested in three experiments: peripheral informative cueing, peripheral uninformative cueing, and central informative cueing. Participants showed a greater effect of cueing in detecting a conjunction of features than in detecting unique features only when attention was oriented by either peripheral or central informative cueing. This differential cueing effect was not observed when attention was oriented by peripheral uninformative cueing. The results suggest that voluntarily oriented attention plays a more important role in feature integration than automatically oriented attention does. The results also pose limits on the generalizability of K. A. Briand's (1998) proposal regarding the role of automatically oriented attention in feature integration.

Adult↗
PubMed2001

Validity of estimating limb muscle volume by bioelectrical impedance.

The present study aimed to investigate the validity of estimating muscle volume by bioelectrical impedance analysis. Bioelectrical impedance and series cross-sectional images of the forearm, upper arm, lower leg, and thigh on the right side were determined in 22 healthy young adult men using a specially designed bioelectrical impedance acquisition system and magnetic resonance imaging (MRI) method, respectively. The impedance index (L(2)/Z) for every segment, calculated as the ratio of segment length squared to the impedance, was significantly correlated to the muscle volume measured by MRI, with r = 0.902-0.976 (P < 0.05). In these relationships, the SE of estimation was 38.4 cm(3) for the forearm, 40.9 cm(3) for the upper arm, 107.2 cm(3) for the lower leg, and 362.3 cm(3) for the thigh. Moreover, isometric torque developed in elbow flexion or extension and knee flexion or extension was significantly correlated to the L(2)/Z values of the upper arm and thigh, respectively, with correlation coefficients of 0.770-0.937 (P < 0.05), which differed insignificantly from those (0.799-0.958; P < 0.05) in the corresponding relationships with the muscle volume measured by MRI of elbow flexors or extensors and knee flexors or extensors. Thus the present study indicates that bioelectrical impedance analysis may be useful to predict the muscle volume and to investigate possible relations between muscle size and strength capability in a limited segment of the upper and lower limbs.

Adult↗
PubMed2001

[Effects of display and memory load on the event-related potentials during visual letter search combined with selection by color].

This study investigated the effects of display and memory load on the event-related potentials (ERPs) in a visual letter search task combined with selection by color. ERPs were recorded from 10 adult subjects, when they were required to judge if test stimuli, which consisted of a horizontal array of five colored alphabets, contained target letters defined by shape and color. The results showed that the increase of display or memory load caused the enlargement of three different negativities. The first and second display load effects were observed in the ERPs at midline central electrode (Cz) between 240-280 ms latency range, and in a posterior-distributed negativity that was the maximum at about 650 ms after the stimulus onset. The third was the anterior-central negativity that was the largest at Cz about 550 ms after the stimulus onset. In contrast to the first two effects, this negativity was enhanced by display or memory load. In discussion, a tentative linkage between these ERP changes and two slave systems of working memory (phonological loop and visuo-spatial sketchpad) was proposed.

Adult↗
PubMed2000

Validity of bioelectrical impedance and ultrasonographic methods for estimating the muscle volume of the upper arm.

The present study aimed to investigate the validity of bioelectrical impedance and ultrasonographic methods for predicting the muscle volume of the upper arm. Bioelectrical impedance of the right upper arm and the thickness of elbow flexor and extensor muscles were measured from 26 healthy young adult men using a specially designed bioelectrical impedance data acquisition system and brightness-mode ultrasound apparatus, respectively. As reference data, the muscle volume (MV(MRI)) of the right upper arm was determined using a magnetic resonance imaging method. The impedance index was calculated as L2/Z, where L is the upper arm length and Z is the impedance of the shoulder to the elbow. The muscle volume (MV(ULT)) was calculated as pi x (d/2)2 L, where d is muscle thickness. L2/Z and MV(ULT) were significantly correlated with MV(MRI) with correlation coefficients of 0.971 and 0.962, respectively. In these relationships, the standard errors of estimation were 44.2 cm3 (6.3%) for L2/Z and 50.7 cm3 (7.2%) for MV(ULT). There was no significant difference between the absolute errors of muscle volumes estimated by L2/Z and MV(ULT): 36.2 (4.8, SEM) cm3 for L2/Z versus 40.3 (5.8) cm3 for MV(ULT). The present results suggest that both bioelectrical impedance and ultrasonographic methods may be useful for predicting the muscle volume of the upper arm.

Adult↗
PubMed1994

ERPs in schizophrenic patients during word recognition task and reaction times.

Event-related brain potentials (ERPs) were recorded in 28 schizophrenic patients and 26 healthy controls during a word recognition task. In each trial, stimuli consisting of S1 (word) and S2 (word or non-word) were presented. The subjects were required to indicate whether S2 was a word or a non-word by pressing buttons. For both groups, a clear N370 was elicited by S2 which were non-word or semantically unrelated to its S1. The N370 amplitude did not differ between the groups. The schizophrenics responded more slowly than the controls, and the latencies of P200 and N370 were longer for patients than for controls. However, these latencies did not differ between the groups when their reaction times were matched.

Adolescent↗
PubMed1994

[Effects of display and memory load on event-related potentials during a visual search task].

We recorded event-related potentials (ERPs) in nine normal adult subjects to investigate the effects of display load (number of positions to be processed) and memory load (memory set size) on ERPs in visual search tasks. The stimulus consisted of a horizontal array of five different alphabets. In search task, subjects were required to respond only to stimuli containing a target letter. In a simple reaction task, they were required to respond to all the stimuli. The results showed that display load affected N200 and NA deflections recorded at occipital and posterior temporal electrodes, although memory load did not affect them. We also found the different effects of display load and memory load on search-related negativities. That is, in latency, search-related negativities with increasing display load appeared before those with memory load. The difference in topography between display and memory load effects on search-related negativities was not confirmed statistically. The validity of ERPs as indices for the visual and memory search processes was discussed.

Adult↗
PubMed1991

The N400 component of event-related potentials in schizophrenic patients: a preliminary study.

ERPs were recorded during a word recognition task to investigate cognitive dysfunction in schizophrenia. Thirteen medicated schizophrenics and 26 normal controls were tested. In each trial a pair of stimuli, S1 (a word) and S2 (a word or a non-word), were presented. The subjects were required to discriminate between a word and a non-word for S2 (lexical decision task). In a related (R) condition, S2 was the antonym of S1 (e.g., brother-sister); in an unrelated (U) condition, S1 and S2 were semantically unrelated (e.g., brother-drive); in the non-word (N) condition, S2 was a non-word (e.g., brother-grofe). The ERPs for S2 were analyzed, and the contextual effects on the ERPs for S2 observed for both the patients and controls. For both groups, in the U and N conditions S2 elicited a large negative-trending deflection (N370). In contrast, in the R condition it elicited only a small negative-trending notch. There was no difference in the amplitude of N370 between the groups, but its latency was more prolonged or its wave shape more extended for the schizophrenics than for the controls. The N400 amplitude is concluded to remain unchanged in schizophrenics.

Adolescent↗