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Biomedical subjects

A Gunji

Publications and source records attributed to A Gunji.

At least 19 recordsLinked to original sources
PubMed2002

The auditory evoked magnetic fields to very high frequency tones.

We studied the auditory evoked magnetic fields (AEFs) in response to pure tones especially at very high frequencies (from 4000 Hz to 40,000 Hz). This is the first systematic study of AEFs using tones above 5000 Hz, the upper audible range of humans, and ultrasound. We performed two experiments. In the first, AEFs were recorded in 12 subjects from both hemispheres under binaural listening conditions. Six types of auditory stimulus (pure tones of five different frequencies: 4000 Hz, 8000 Hz, 10,000 Hz, 12,000 Hz, 14,000 Hz, and a click sound as the target stimulus) were used. In the second experiment, we used 1000 Hz, 15,000 Hz, and two ultrasounds with frequencies of 20,000 Hz and 40,000 Hz. The subjects could detect all stimuli in the first experiment but not the ultrasounds in the second experiment. We analyzed N1m, the main response with approximately 100 ms in peak latency, and made the following findings. (1) N1m responses to the tones up to 12,000 Hz were clearly recorded from at least one hemisphere in all 12 subjects. N1m for 14,000 Hz was identified in at least one hemisphere in 10 subjects, and in both hemispheres in six subjects. No significant response could be identified to ultrasounds over 20,000 Hz. (2) The amplitude of the N1m to the tones above 8000 Hz was significantly smaller than that to 4000 Hz in both hemispheres. There was a tendency for the peak latency of the N1m to be longer for the tones with higher frequencies, but no significant change was found. (3) The equivalent current dipole (ECD) of the N1m was located in the auditory cortex. There was a tendency for the ECD for the tones with higher frequencies to lie in more medial and posterior areas, but no significant change was found. (4) As for the interhemispheric difference, the N1m amplitude for all frequency tones was significantly larger and the ECDs were estimated to be located more anterior and medial in the right hemisphere than the left. The priority of the right hemisphere, that is the larger amplitude, for very high frequency tones was confirmed. (5) The orientation of the ECD in the left hemisphere became significantly more vertical the higher the tones. This result was consistent with previous studies which revealed the sensitivity of the frequency difference in the left hemisphere. From these findings we suggest that tonotopy in the auditory cortex exists up to the upper limit of audible range within the small area, where the directly air-conducted ultrasounds are not reflected.

Acoustic Stimulation↗
PubMed2001

Hearing the sound of silence: a magnetoencephalographic study.

We visualized the brain activity for retrieval imagery of a sound using dual 37-channel magnetometers in seven right-handed healthy subjects. A soundless video image of a hammer striking an anvil was presented on a screen. Significantly larger evoked magnetic fields were recorded, dominantly in the right hemisphere, in six subjects when they imagined the sound than when they did not. The initial peak of the response was 151.0 +/- 26.5 ms (mean +/- s.d.) after the blow. Equivalent current dipoles (ECDs) for the responses recorded from the right hemisphere were located around the inferior frontal sulcus in three subjects and in the insular region in three subjects, but reliable ECDs were not estimated from the left hemisphere. The results suggested that the initial activity for sound retrieval imagery appeared around the inferior frontal and insular areas, dominantly in the right hemisphere.

Adult↗
PubMed2001

Automatic discriminative sensitivity inside temporal window of sensory memory as a function of time.

Neural representation of preceding sound-patterns stored in the human brain, as reflected by mismatch negativity (MMN) related to the automatic discriminative process, is restricted to a duration of 160-170 ms due to the short form of auditory sensory memory termed the temporal window of integration (TWI). To examine the temporal uniformity of deviation-sensitivity inside TWI of sensory memory, magnetic MMN (MMNm) responses were measured with a dual 37-channel magnetometer for complex sounds of 170 ms duration containing an omitted (silent) segment. Frequent standard stimuli (probability of 80%) consisted of five tone segments. Deviant stimuli were different from standard stimuli in that one of four segments was occasionally (probability of 5%) omitted and replaced by a silent segment. The stimulus duration of 170 ms was intended to correspond to the postulated duration of TWI. When the silent segment occurred later in deviant stimulus, the MMNm peak amplitude was attenuated and MMNm peak latency, measured from the onset of each silent segment, was delayed. Thus, automatic deviation-detection sensitivity declines nonlinearly toward the end of TWI in auditory sensory memory. In the second experiment, two types of deviant stimuli, which differed from each other only in the period after the occurrence of the silent segment, elicited MMNm with the same peak latency but with a different peak amplitude. Thus, mismatch process is triggered at the moment of change but still lasts after the detection of deviation. In other words, both standard and deviant stimuli are treated as a unitary event within a TWI.

Acoustic Stimulation↗
PubMed2001

Auditory response following vocalization: a magnetoencephalographic study.

OBJECTIVE: We recorded vocalization-related cortical fields (VRCF) under complete masking of a subject's own voice to identify the auditory component evoked by a subject's own voice in the VRCF complex. METHODS: We recorded VRCF during simple vowel (/u/) vocalization in 10 right-handed healthy volunteers under two conditions: (1) no masking (control) and (2) masking of the subject's own voice by weighted-white noise during vocalization. In the second experiment, we recorded auditory evoked magnetic fields (AEF) following stimulation of a speech sound applied by voice-recorder. RESULTS: The onset of VRCF appeared gradually before the vocalization onset, and a clear phase-reversed deflection was identified after the onset of vocalization. The difference waveform obtained by subtracting the VRCF of the masking condition from that of the control showed a deflection (1M) at 81.3+/-20.5 (mean+/-SD) ms after the onset of vocalization, but there was no consistent deflection before the vocalization onset. The AEF following voice sound in the second experiment showed the M100 component at 94.3+/-18.4 ms. The equivalent current dipole of the 1M component for different waveforms was located close in the auditory cortex to that of the M100 for AEF waveforms in each hemisphere. CONCLUSION: We successfully separated the auditory feedback response from the VRCF complex, using an adequate masking condition during vocalization of a subject's own voice. The masking effect was crucial to the auditory feedback process after the onset of vocalization. The present results suggested that the 1M component was mainly generated from the auditory feedback process by the subject's own voice. The activated auditory area for simple own voice might be similar to that for simple external sound.

Adult↗
PubMed2001

Inactivity and muscle: effect of resistance training during bed rest on muscle size in the lower limb.

The present study aimed to investigate the effect of dynamic leg press training on the physiological cross-sectional areas (PCSAs) of human lower limb muscles during 20 days of 6 degrees head-down tilt bed rest. Five healthy men comprised the resistance training group (BR-Tr) and data from two previous studies were used to derive a 10-man control group (BR-Cont). The BR-Tr performed two sessions (morning and afternoon session) of dynamic leg press action including knee extension and plantar flexion daily for the bed rest period: (1) three sets of 10 repetitions at 90% of maximum load and (2) 40% of maximum load to exhaustion. The PCSAs of the knee extensor (KE), knee flexor (KF), plantar flexor (PF), and dorsiflexor muscle groups were estimated using serial axial magnetic resonance (MR) images of the right-thigh and leg. After the bed rest period, the BR-Tr showed a significant increase in the PCSA of the KE. Although PCSA of the KF in two groups significantly decreased after bed rest, percentage of change in PCSA of the biceps femoris (long head) and semitendinosus muscles in the BR-Tr, which occupied approximately 70% of the KF, was significantly higher than those in the BR-Cont. Both the BR-Tr and BR-Cont groups showed significant decreases in the PCSA of PF with similar magnitude of 11.6% (P < 0.001) and 11.9% (P < 0.001), respectively. These results suggest that dynamic leg press training during bed rest can prevent deteriorating of the KE and a part of KF, but not the calf muscles.

Adult↗
PubMed2001

Development of "Standards for the Evaluation of Hospital Infection Control Policies and Procedures, the Second Version".

The Japan Society for Quality in Health Care (JSQua) created "Standards for the Evaluation of Hospital Infection Control Policies and Procedures, the First Version" in 1998 and carried out third-party surveys. Through the experience of those surveys, we revised the standards and created a second version in 1999. The surveyors felt that in using the second version of the standards it would be easier to evaluate the quality of hospital care and that these standards would be more widely applied.

Cross Infection↗
PubMed2000

The masking effect in foreign speech sounds perception revealed by neuromagnetic responses.

The backward masking effect on non-native consonants by a following vowel was examined using neuromagnetic responses to synthesized speech sounds. Native speakers of Japanese were presented with sequences of frequent (85%) and infrequent (15%) speech sounds (/ra/ and /la/ respectively, no /l/ /r/ contrast in Japanese language). The duration of the stimuli was 110 ms in a short session and 150 ms in a long session. In the short session, the stimuli were terminated in the course of the transition from the consonant to the vowel to diminish the masking effect from the vowel part. A distinct magnetic counterpart of mismatch negativity (MMNm) was observed for the short session, whereas a smaller MMNm was observed for the long session.

Adult↗
PubMed2000

Leg-press resistance training during 20 days of 6 degrees head-down-tilt bed rest prevents muscle deconditioning.

The purpose of this study was to investigate the effects of resistance training on the morphological and functional properties of human lower limb muscles during 20 days of 6 degrees head-down-tilt bed rest. Nine men were randomly assigned to the resistance training group (BR-Tr, n = 5) or the non-training, control group (BR-Cont, n = 4). Isometric leg-press exercises were performed: 3 s x 30 repetitions (30 s rest between repetitions) daily for 20 days during the bed-rest period. Serial axial magnetic resonance images were taken from the right thigh and leg muscles, and muscle volume, muscle length, and fibre length were estimated. The physiological cross-sectional areas (PCSAs) of the knee extensor, knee flexor, ankle plantarflexor, and ankle dorsiflexor (tibialis anterior) muscle groups were determined as muscle volume multiplied by the cosine of the angle of fibre pennation divided by fibre length. Maximum voluntary contraction (MVC) during knee extension was measured. No significant changes were observed in the PCSA of the knee extensor muscles in BR-Tr group, whereas the PCSA in the BR-Cont group decreased by 7.8%. The PCSA of the knee flexor and plantarflexor muscles in the BR-Tr group and BR-Cont group significantly decreased after bed rest (knee flexors, 10.2% and 11.5%; plantarflexors, 13.0% and 12.8%, respectively). However, in both groups bed rest had no effect on the muscle volume and PCSA of the tibialis anterior. MVC was maintained by resistance training in the BR-Tr group (decreased by 1%). In contrast, a decline of strength was observed in the BR-Cont group (-16%), but this result was not statistically significant. These results suggest that isometric leg-press training prevents the deconditioning (i.e. atrophy and decline of strength) of the knee extensor muscle group.

Adult↗
PubMed2000

Magnetic response of human extrastriate cortex in the detection of coherent and incoherent motion.

Although direction selectivity is a cardinal property of neurons in the visual motion detection system, movement of numerous elements without global direction (incoherent motion) has been shown to activate human and monkey visual systems, as does coherent motion which has global direction. We used magnetoencephalography to investigate the neural process underlying responses to these types of motions in the human extrastriate cortex. Both motions were created using a random dot kinematogram and four speeds (0, 0.6, 9.6 and 25 degrees /s). The visual stimuli were composed of two successive motions at different speeds; a coherent motion at a certain speed that changed to incoherent motion at another speed or vice versa. Magnetic responses to the change in motion consisted of a few components, the first of which was always largest. The peak latency of the first component was inversely related to the speed of the preceding motion, but for both motions it was not affected by the speed of the subsequent motion. For each subject, the estimated origin of the first component was always in the extrastriate cortex, and this changed with the speed of the preceding motion. For both motions, the location for the slower preceding motion was lateral to that for the faster preceding motion. Although the latency changes of the two motions differed, their overall response properties were markedly similar. These findings show that the speed of incoherent motion is represented in the human extrastriate cortex neurons to the same degree as coherent motion. We consider that the human visual system has a distinct neural mechanism to perceive random dots' motion even though they do not move in a specific direction as a whole.

Adult↗
PubMed2000

Hemispheric lateralization in an analysis of speech sounds. Left hemisphere dominance replicated in Japanese subjects.

Evoked magnetic responses to speech sounds [R. Näätänen, A. Lehtokoski, M. Lennes, M. Cheour, M. Huotilainen, A. Iivonen, M. Vainio, P. Alku, R.J. Ilmoniemi, A. Luuk, J. Allik, J. Sinkkonen and K. Alho, Language-specific phoneme representations revealed by electric and magnetic brain responses. Nature, 385 (1997) 432-434.] were recorded from 13 Japanese subjects (right-handed). Infrequently presented vowels ([o]) among repetitive vowels ([e]) elicited the magnetic counterpart of mismatch negativity, MMNm (Bilateral, nine subjects; Left hemisphere alone, three subjects; Right hemisphere alone, one subject). The estimated source of the MMNm was stronger in the left than in the right auditory cortex. The sources were located posteriorly in the left than in the right auditory cortex. These findings are consistent with the results obtained in Finnish [R. Näätänen, A. Lehtokoski, M. Lennes, M. Cheour, M. Huotilainen, A. Iivonen, M.Vainio, P.Alku, R.J. Ilmoniemi, A. Luuk, J. Allik, J. Sinkkonen and K. Alho, Language-specific phoneme representations revealed by electric and magnetic brain responses. Nature, 385 (1997) 432-434.][T. Rinne, K. Alho, P. Alku, M. Holi, J. Sinkkonen, J. Virtanen, O. Bertrand and R. Näätänen, Analysis of speech sounds is left-hemisphere predominant at 100-150 ms after sound onset. Neuroreport, 10 (1999) 1113-1117.] and English [K. Alho, J.F. Connolly, M. Cheour, A. Lehtokoski, M. Huotilainen, J. Virtanen, R. Aulanko and R.J. Ilmoniemi, Hemispheric lateralization in preattentive processing of speech sounds. Neurosci. Lett., 258 (1998) 9-12.] subjects. Instead of the P1m observed in Finnish [M. Tervaniemi, A. Kujala, K. Alho, J. Virtanen, R.J. Ilmoniemi and R. Näätänen, Functional specialization of the human auditory cortex in processing phonetic and musical sounds: A magnetoencephalographic (MEG) study. Neuroimage, 9 (1999) 330-336.] and English [K. Alho, J. F. Connolly, M. Cheour, A. Lehtokoski, M. Huotilainen, J. Virtanen, R. Aulanko and R.J. Ilmoniemi, Hemispheric lateralization in preattentive processing of speech sounds. Neurosci. Lett., 258 (1998) 9-12.] subjects, prior to the MMNm, M60, was elicited by both rare and frequent sounds. Both MMNm and M60 sources were posteriorly located in the left than the right hemisphere.

Adult↗
PubMed2000

Spatiotemporal source analysis of vocalization-associated magnetic fields.

The vocalization-related cortical fields (VRCF) following vowel vocalization were studied by magnetoencephalography (MEG) in eight normal subjects. A multiple-source model, BESA (Brain Electric Source Analysis), was applied to elucidate the generating mechanism of VRCF in the period from 150 ms before to 150 ms after the onset of vocalization. Six sources provided satisfactory solutions for VRCF activities during that period. Sources 1 and 2, which were activated from approximately 150 ms before the vocalization onset, were located in laryngeal motor areas of the left and right hemispheres, respectively. Sources 5 and 6 were located in the truncal motor area in each hemisphere, and they were very similar to sources 1 and 2 in terms of temporal change of activities. Sources 3 and 4 were located in the auditory cortices of the left and right hemispheres, respectively, and they appeared to be activated just after the vocalization onset. However, all six sources were temporally overlapped in the period approximately 0-100 ms after the vocalization onset. The present results suggested that the bilateral motor cortices, probably laryngeal and truncal areas, were activated just before the vocalization. We considered that the activities of the bilateral auditory areas after the vocalization were the response of the subject's central auditory system to his/her own voice. The motor and auditory activities were temporally overlapped, and BESA was very useful to separate the activities of each source.

Adult↗
PubMed2000

Identification of auditory evoked potentials of one's own voice.

OBJECTIVE: We recorded vocalization related cortical potentials (VRCP) with complete masking of one's own voice, and separated the feedback auditory potentials following vocalization from the VRCP complex. METHODS: We used 9 right-handed healthy subjects. We recorded VRCP during simple vowel vocalizing under two conditions, (1) without masking (control); (2) with masking. Electroencephalography (EEG) was recorded from seven areas, Fz, Cz, Pz, C3, C4, T3 and T4, of the International 10-20 system. The trigger point was the onset of vocalized sound recorded through a microphone. RESULTS: In both control and masking conditions, similar negative potentials prior to the vocalization were observed. However, the amplitude just after the onset of vocalization was significantly smaller in the masking than the control condition. The difference waveform, obtained by subtracting the waveforms in the masking from those in the control condition, showed a simple negative peak after the vocalization onset. CONCLUSIONS: We considered that the difference waveform indicated the auditory evoked potentials following own voice in the auditory feedback process. Since there was no difference of the negative potentials before vocalization between the two conditions, we speculated that the masking effect on auditory feedback following vocalization was crucial, while its effect on the preparatory process of simple vocalization might be minimal.

Acoustic Stimulation↗
PubMed2000

Risk factors for ischemic heart disease in an urban area of Japan: a case-control study in AMHTS.

OBJECTIVES: In Japan controversy exists as to whether or not the risk factors for ischemic heart disease (IHD) are the same as in western countries. We conducted a case-control study on IHD to clarify the risk factors in males in an urban area of Japan using our automated multiphasic health testing and services (AMHTS) system. METHOD: Cases were the clients who took the health check-up between January 1987 and July 1994 and had onset of IHD after the check-up. For each case five clients were selected as controls by conditional matching. The check-up data were compared between cases and controls 11 years, 6 years and just before the onset of the heart diseases. RESULTS: The statistically significant items were as follows: (1) Eleven years before the onset: Total cholesterol (T-Chol) for myocardial infarction (MI), and fasting blood sugar (FBS) for angina pectoris (AP). (2) Six years before the onset: T-Chol, electrocardiographic (ECG) findings and the complaint of palpitation or breathlessness for MI, and FBS and palpitation or breathlessness for AP. (3) Just before the onset: T-Chol, the complaint of chest pain, FBS, smoking index and hypertensive status for MI and palpitation or breathlessness, ECG findings, chest pain, systolic blood pressure and erythrocyte sedimentation rate at 60 minutes for AP. In conclusion, the risk factors for MI in males in an urban area of Japan are the same as in western countries. The most significant risk factor for AP in males in an urban area of Japan is fasting blood sugar.

Adult↗
PubMed2000

[A study on resource based relative values for visiting nursing services].

PURPOSE: The purpose of this study was to investigate the resource based relative values of visiting nursing services, and to analyze the relationships between the relative values and the dimensions of nursing service(time, mental effort and physical effort). METHODS: We interviewed nurses at 20 Home-visit nursing care stations (HVNCS) in the Metropolitan area using the resource based relative value questionnaires. We asked nurses about relative values of "Total Work", and also measured relative weight of 3 dimensions of nursing services. Total Work was defined as comprehensive evaluation of nursing services, with careful consideration of intensity as well as duration. With the dependent variable as Total Work and independent variables as the 3 dimensions, multiple regression analyses were carried out. Furthermore we examined the degree of influence on Total Work by service type and individual respondent. To examine the validity of the results, we timed nursing services and compared the measured time with the answered time. RESULTS: The 107 respondents were all female and their average age was 36.6 years old. They had HVNCS experience of 2.2 years and 95.3% nurses had experience of hospital nursing. "Total Work" and 3 dimension scores were standardized using common logarithms. "Total Work" of every service significantly differed among service types. The 3 dimensions explained 54.6% of Total Work in the multiple regression analysis. Service type explained 3.3% of Total Work. Individual respondent explained 16.0% of Total Work. Answered time and measured time were not significantly different with nursing services. CONCLUSIONS: Although Total Work was somewhat influenced by individual respondent, most of variation was explained by 3 dimensions. Thus, it could be concluded that Total Work is an index of nursing resource input. A further investigation about influence of patients' condition on Total Work is necessary in the future.

Adult↗
PubMed1999

Relatively shorter but intensive isotonic exercise in legs prevented the decrease in maximal aerobic power after 20 days of head down tilt bed rest in man.

As a countermeasures for the decrease in maximal oxygen uptake (VO2max) during prolong simulated weightlessness, it has been suggested that intensive isotonic legs exercise was useful. The reason is possibly that a dynamic and intensive resistance exercise training makes to maintain not only the volume of exercising muscles but also cardiac output. For the reason, it has been studied the effects of 3 different exercise training on VO2max during simulated weightlessness.

Bed Rest↗
PubMed1999

Degraded diet induced thermogenesis induced by 20 days of 6 degrees head down bed rest and effect of resistance training.

In the 21st century, our dream of living in a space will finally become reality. To understand the effects of microgravity on energy expenditure and possible countermeasure against them is important to maintain human health in space. Diet Induced Thermogenesis (DIT) is an increase in energy expenditure after ingestion of a meal, and accounts for 10% of total daily energy expenditure. Recently, the important role of DIT in regulating obesity is suggested. Basal Energy Expenditure (BEE), on the other hand, is the minimum energy expenditure required to keep on living, and accounts for 60-75% of total energy expenditure. Despite the importance of DIT, no information about DIT in microgravity and possible effects of exercise training is available. Therefore, we aimed to investigate, first, the effects of 20-days of 6 degrees head down tilting bed rest (HDBR) on postabsorptive energy expenditure (PEE), DIT, and BEE. Second, the effects of resistance training during HDBR on DIT and BEE.

Adult↗