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Biomedical subjects

G H Yue

Publications and source records attributed to G H Yue.

17 recordsLinked to original sources
PubMed2001

Relationship between muscle output and functional MRI-measured brain activation.

The relationship between functional MRI (fMRI)-measured brain signal and muscle force and or electromyogram (EMG) is critical in interpreting fMRI data and understanding the control mechanisms of voluntary motor actions. We designed a system that could record joint force and surface EMG online with fMRI data. High-quality force and EMG data were obtained while maintaining the quality of the fMRI brain images. Using this system, we determined the relationship between fMRI-measured brain activation and handgrip force and between fMRI-measured brain signal and EMG of extrinsic finger muscles. Ten volunteers participated in the experiments (only seven subjects' data were analyzed due to excessive noise in the fMRI data of three subjects). The participants exerted 20%, 35%, 50%, 65%, and 80% of the maximal force. During each contraction period, handgrip force, surface EMG of the finger flexor and extensor muscles, and fMRI brain images were acquired. The degree of muscle activation (force and EMG) was directly proportional to the amplitude of the brain signal determined by fMRI in the entire brain and in a number of motor function-related cortical fields, including primary motor, sensory regions, supplementary motor area, premotor, prefrontal, parietal and cingulate cortices, and cerebellum. All the examined brain areas demonstrated a similar relationship between the fMRI signal and force. A stronger fMRI signal during higher force indicates that more cortical output neurons and/or interneurons may participate in generating descending commands and/or processing additional sensory information. The similarity in the relationship between muscle output and fMRI signal in the cortical regions suggests that correlated or networked activation among a number of cortical fields may be necessary for controlling precise static force of finger muscles.

Adult↗
PubMed2001

Effects of aging on hand function.

OBJECTIVES: The purpose of this study was to quantify age-induced changes in handgrip and finger-pinch strength, ability to maintain a steady submaximal finger pinch force and pinch posture, speed in relocating small objects with finger grip, and ability to discriminate two identical mechanical stimuli applied to the finger tip. DESIGN: A cross-sectional study. SETTINGS: Greater Cleveland area of Ohio. PARTICIPANTS: Healthy, independent, young (n = 27, range 20-35 years) and older (n = 28, range 65-79 years) subjects. MEASUREMENTS: Handgrip strength, maximum pinch force (MPF), ability to maintain a steady pinch force at three relative force levels (5%, 10%, and 20% MPF) and three absolute force levels (2.5 Newtons (N), 4 N, and 8 N), ability to maintain a precision pinch posture, speed in relocating pegs from a nearby location onto the pegboard, and the shortest distance for discriminating two stimuli were measured in both young and older groups. RESULTS: Compared with young subjects, the older group's handgrip force was 30% weaker (P < .001), MPF was 26% lower (P < .05), and ability to maintain steady submaximal pinch force and a precision pinch posture was significantly less (P < .05). The time taken to relocate the pegs and the distance needed to discriminate two identical stimuli increased significantly with age (P < .01). The decrease in the ability to maintain steady submaximal pinch force was more pronounced in women than men. CONCLUSION: Aging has a degenerative effect on hand function, including declines in hand and finger strength and ability to control submaximal pinch force and maintain a steady precision pinch posture, manual speed, and hand sensation.

Adult↗
PubMed2001

Skilled finger movement exercise improves hand function.

BACKGROUND: Aging is accompanied by a marked decline in muscle strength and ability to maintain steady submaximal force. Studies have shown that exercise programs can improve age-related regression of hand function in elderly individuals. The purpose of this study was to train elderly subjects to perform skilled finger movements and to evaluate the changes in hand function involving skillful use of finger pinch. METHODS: Grip strength, maximum pinch force (MPF), steadiness of pinch force at 5%, 10%, and 20% MPF, M wave, and Hoffman (H) reflex were measured. Fourteen elderly subjects were trained with skilled finger movements, and their performance involving finger pinch was measured. RESULTS: Compared with untrained elderly subjects, the trained older adults significantly (p <.05) improved their ability to control submaximal pinch force, to maintain a steady hand posture, and to relocate a small object quickly with finger grip. The amplitude of H reflex increased significantly for the trained group. CONCLUSIONS: Skilled finger movement training improves the ability to control submaximal pinch force, hand steadiness, and manual speed in elderly subjects; these improvements may be due to training-induced adaptations in the central and peripheral nervous systems.

Activities of Daily Living↗
PubMed2001

Greater movement-related cortical potential during human eccentric versus concentric muscle contractions.

Despite abundant evidence that different nervous system control strategies may exist for human concentric and eccentric muscle contractions, no data are available to indicate that the brain signal differs for eccentric versus concentric muscle actions. The purpose of this study was to evaluate electroencephalography (EEG)-derived movement-related cortical potential (MRCP) and to determine whether the level of MRCP-measured cortical activation differs between the two types of muscle activities. Eight healthy subjects performed 50 voluntary eccentric and 50 voluntary concentric elbow flexor contractions against a load equal to 10% body weight. Surface EEG signals from four scalp locations overlying sensorimotor-related cortical areas in the frontal and parietal lobes were measured along with kinetic and kinematic information from the muscle and joint. MRCP was derived from the EEG signals of the eccentric and concentric muscle contractions. Although the elbow flexor muscle activation (EMG) was lower during eccentric than concentric actions, the amplitude of two major MRCP components-one related to movement planning and execution and the other associated with feedback signals from the peripheral systems-was significantly greater for eccentric than for concentric actions. The MRCP onset time for the eccentric task occurred earlier than that for the concentric task. The greater cortical signal for eccentric muscle actions suggests that the brain probably plans and programs eccentric movements differently from concentric muscle tasks.

Adult↗
PubMed2001

Functional magnetic resonance imaging before and after ventriculoperitoneal shunting for hydrocephalus--case report.

A 70-year-old man with hydrocephalus was examined with functional magnetic resonance (fMR) imaging before and after ventriculoperitoneal shunting. Preoperatively, activation by right hand exercise revealed only a slight signal increase in the peri-rolandic area. However, 3 months after ventriculoperitoneal shunting, a significant signal increase was observed. fMR imaging may detect activity-related improvement of cerebral blood flow responses in patients with hydrocephalus after surgical treatment.

Aged↗
PubMed2000

Simultaneous measurement of human joint force, surface electromyograms, and functional MRI-measured brain activation.

Functional magnetic resonance imaging (fMRI) has been increasingly used in studying human brain function given its non-invasive feature and good spatial resolution. However, difficulties in acquiring data from peripheral (e.g. information from muscle) during fMRI studies of motor function hinder interpretation of fMRI data and designing more sophisticated investigations. Here we describe a system that was designed to concurrently measure handgrip force, surface electromyograms (EMG) of finger flexor and extensor muscles, and fMRI of human brain. The system included a pressure transducer built in a hydraulic environment, a heavily shielded EMG recording element, and a visual feedback structure for online monitoring of force and/or EMG signal, by the subject positioned in the scanner during an fMRI experiment. System evaluation and subsequent fMRI motor function studies have indicated that by using this system, high quality force and EMG signals can be recorded without sacrificing the quality of the fMRI data.

Brain Mapping↗
PubMed2000

Measurement of tissue electrical impedance confirms stereotactically localized internal segment of the globus pallidus during surgery.

Lesions surgically made in the internal segment of the posteroventral globus pallidus (Gpi) reduce many medically intractable symptoms in patients with Parkinson's disease. The Gpi is localized for pallidotomy by stereotactic procedures. We sought to confirm the stereotactically localized Gpi segment by measuring impedance between the tip of an active electrode that was advanced toward the target and a remote reference electrode. A stereotactic instrument was used to place an active electrode in 53 conscious patients undergoing pallidotomy. The electrode was manually advanced slowly toward the Gpi segment by a microdrive. Impedance was measured every 10 mm initially and every 1 mm in the final 10 mm of the electrode's advancement, using an impedance monitor interconnected with a lesion generator. Measurements were continued for several millimeters after each patient's target was reached. Impedance values ranged from 250 to 350 ohms throughout of the electrode passage. Impedance increased by 25-35 ohms at 1-3 mm before the center of the target and then dropped abruptly when the electrode passed the target. Impedance values depended strongly on the electrode's configuration. The impedance measurement confirmed the location of each surgical target identified by stereotactic navigation. The accuracy of the impedance measurement is acceptable, and the procedure can be recommended as an aid to confirm the stereotactically localized Gpi during neurological surgery.

Adult↗
PubMed2000

Brain activation during human finger extension and flexion movements.

Corticospinal projections to the motor neuron pool of upper-limb extensor muscles have been reported to differ from those of the flexor muscles in humans and other primates. The influence of this difference on the central nervous system control for extension and flexion movements is unknown. Cortical activation during thumb extension and flexion movements of eight human volunteers was measured using functional magnetic resonance imaging (fMRI), which detects signal changes caused by an alteration in the local blood oxygenation level. Although the relative activity of the extensor and flexor muscles of the thumb was similar, the brain volume activated during extension was substantially larger than that during flexion. These fMRI results were confirmed by measurements of EEG-derived movement-related cortical potential. Higher brain activity during thumb extension movement may be a result of differential corticospinal, and possibly other pathway projections to the motoneuron pools of extensor and flexor muscles of upper the extremities.

Adult↗
PubMed2000

Evidence of inability to fully activate human limb muscle.

The purpose of this study was to determine whether muscle activation level estimated by twitch interpolation technique was different when an electrical stimulus was applied during a dynamic force (DF; force rising) task from that when the stimulus was applied during a static force (SF; constant force) task. Fourteen subjects performed voluntary SF and DF contractions involving isometric elbow flexion at seven voluntary force levels. At each level, the electrical stimulation was applied to the surface of the biceps brachii muscle when the force was steady (SF task) and when the force was rising (DF task). The voluntary activation level of the biceps brachii muscle during the SF maximal voluntary contraction (MVC) was 98.5% and that during the DF MVC task was significantly lower (94.5%; P < 0.05). The motoneurons and/or muscle fibers may become more excitable during the DF task so that the same stimulus can recruit those that are otherwise less excitable during the SF task.

Adolescent↗
PubMed2000

Relationship between motor activity-related cortical potential and voluntary muscle activation.

The purpose of this study was to investigate the relationship between EEG-derived motor activity-related cortical potential (MRCP) and voluntary muscle activation. Eight healthy volunteers participated in two experimental sessions. In one session, subjects performed isometric elbow-flexion contractions at four intensity levels [10%, 35%, 60%, and 85% maximal voluntary contraction (MVC)]. In another session, a given elbow-flexion force (35% MVC) was generated at three different rates (slow, intermediate, and fast). Thirty to 40 contractions were performed at each force level or rate. EEG signals were recorded from the scalp overlying the supplementary motor area (SMA) and contralateral sensorimotor cortex, and EMG signals were recorded from the skin surface overlying the belly of the biceps brachii and brachioradialis muscles during all contractions. In each trial, the force was used as the triggering signal for MRCP averaging. MRCP amplitude was measured from the beginning to the peak of the negative slope. The magnitude of MRCP from both EEG recording locations (sensorimotor cortex and SMA) was highly correlated with elbow-flexion force, rate of rising of force, and muscle EMG signals. These results suggest that MRCP represents cortical motor commands that scale the level of muscle activation.

Adult↗
PubMed2000

Identification of QTL affecting important traits on porcine chromosome 12.

To screen the whole porcine chromosome 12 for QTL affecting economically important traits, ten genetic markers were genotyped in two F2 populations generated from the cross of genetically diverse breeds: European Wild pig and commercial pig breed Pietrain (W x P), and Chinese Meishan and Pietrain (M x P). Fifty-one traits were recorded. A least squares method was used for chromosome-wide screening for QTL. An association analysis between genotypes at the GH locus and traits was also carried out. The least squares analysis did not reveal the presence of genome-wide significant QTL affecting the traits, while the association study showed significant (P < 0.01) associations between GH genotypes and fatness traits in M x P, but not in W x P. F2 pigs carrying the genotype C1A2/C4A2 at the GH locus displayed the thinnest backfat (21.76 mm), while the ones carrying the genotype C2A2/C2A2 had the thickest (31.41 mm).

Animals↗
PubMed1999

Rapid and precise genotyping of porcine microsatellites.

Microsatellites are useful markers for genetic mapping and linkage analysis because they are highly polymorphic, abundant in genomes and relatively easily scored with polymerase chain reaction (PCR). A rapid genotyping system for microsatellites was developed, which included multiplex PCRs, multiple use of Hydrolink gels, automated fluorescent detection of fragments on an A.L.F. DNA sequencer, automatic assignment of alleles to each locus and verification of genotypes with a self-developed computer program "Fragtest". Eight multiplex PCRs have been developed to genotype 29 microsatellites for genetic and quantitative trait loci (QTL) mapping on pig chromosomes 6, 7, 12 and 13. Three to six microsatellites could be amplified in one multiplex PCR. Each multiplex reaction required only different concentrations of each pair of primers and a low concentration of dNTP (100 microM). A dNTP concentration of 100 microM proved to be optimal for the coamplification of microsatellites under the concentration of 1.5 mM MgCl2. Using four internal size standards added in each sample, the 5% Hydrolink gel could subsequently be used up to five times (total running time of 500 min) on the A.L.F. automated sequencer without significant loss of resolution and precision of fragment length analysis. Automatic assignment of alleles on each locus using "Fragtest" significantly increased the efficiency and precision of the genotyping. This system is thus a rapid, cheap, and highly discriminating genotyping system.

Animals↗
PubMed1999

Older adults exhibit a reduced ability to fully activate their biceps brachii muscle.

BACKGROUND: Voluntary muscle strength declines significantly in older adults. One contributing factor to the strength loss is muscle atrophy developed in old age. Whether the ability to maximally activate the muscle decreases with age, however, is unknown. This study was intended to determine if the central nervous system command to maximally activate the biceps brachii muscle deteriorates with age. METHODS: Electrical stimulation pulses were applied to the skin overlying the biceps brachii muscle during maximal voluntary elbow-flexion contractions. The magnitude of force evoked on the maximal voluntary force was measured to determine the activation level (AL) of the muscle. RESULTS: The AL was 94% for the elderly group and 97% for the young group (100% AL indicates complete activation). The AL for both the elderly and young groups was significantly (p<.05) lower than 100%. The AL of the elderly group was significantly (p<.05) lower than that of the young group. CONCLUSIONS: The loss of voluntary strength in older adults is a mixed result of muscle atrophy and a reduced ability to fully activate muscle.

Adolescent↗
PubMed1997

Task-dependent effect of limb immobilization on the fatigability of the elbow flexor muscles in humans.

Because short-term limb immobilization produces selective adaptations in the neuromuscular system that probably interact with the task-dependent expression of muscle fatigue, the purpose of this study was to determine the effects of limb immobilization on the ability of human subjects to sustain isometric contractions at low and moderate submaximal forces. Four weeks of elbow joint immobilization caused a substantial decrease in the daily activity of biceps brachii during immobilization, a significant reduction in the cross-sectional area and volume of the elbow flexor muscles as measured by magnetic resonance imaging, and a decline in the maximum voluntary contraction (MVC) activation and force of the elbow flexor muscles. Immobilization had a task-dependent effect on muscle fatigue with a substantially increased endurance time (reduced fatigability) at a low force (20% MVC) and no statistical effect at a moderate force (65% MVC). Despite atrophy of the elbow flexor muscles due to the immobilization, the twitch force elicited in biceps brachii by electrical stimulation was greater after immobilization. The selective improvement of fatigue resistance for the low-force contraction and the absence of a change in the time course of the twitch suggests that the immobilization-induced adaptations included an improved efficacy of some excitation-contraction processes and underscored the major role of these mechanisms in determining the endurance time for low-force, long-duration contractions.

Adult↗
PubMed1994

Training-related enhancement in the control of motor output in elderly humans.

The increase in motor unit force that occurs with aging has been hypothesized to cause a decline in the ability to maintain a constant submaximal force. To test this hypothesis, young and elderly subjects performed a 12-wk strength-training program that was intended to increase motor unit force. The training program caused similar increases (%initial) in the training load (137.4 +/- 17.2%), twitch force (23.1 +/- 7.4%), and maximum voluntary contraction force (39.2 +/- 6.8%) of the first dorsal interosseus muscle for the young and elderly subjects. The increase in strength was associated with a modest increase in muscle volume (7% of initial value) and a nonmonotonic increase in the surface-recorded electromyogram that was significant at week 8 but not at week 12. The elderly subjects reduced the variability in force at the lower target forces (2.5, 5.0, and 20.0% maximum voluntary contraction force). This improvement, however, was unrelated to changes in the distribution of motor unit forces, which was not consistent with the hypothesis that the greater coefficient of variation for the force fluctuations is due to increased motor unit forces.

Adolescent↗