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Biomedical subjects

Jen-Chuen Hsieh

Publications and source records attributed to Jen-Chuen Hsieh.

At least 19 recordsLinked to original sources
PubMed2007

Classification of spatiotemporal hemodynamics from brain perfusion MR images using expectation-maximization estimation with finite mixture of multivariate gaussian distributions.

The ability to cluster different perfusion compartments in the brain is critical for analyzing brain perfusion. This study presents a method based on a mixture of multivariate Gaussians (MoMG) and the expectation-maximization (EM) algorithm to dissect various perfusion compartments from dynamic susceptibility contrast (DSC) MR images so that each compartment comprises pixels of similar signal-time curves. This EM-based method provides an objective way to 1) delineate an area to serve as the in-plane arterial input function (AIF) of the feeding artery for adjacent tissues to better quantify the relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), and mean transit time (MTT); 2) demarcate regions with abnormal perfusion derangement to facilitate diagnosis; and 3) obtain parametric maps with supplementary information, such as temporal scenarios and recirculation of contrast agent. Results from normal subjects show that perfusion cascade manifests (in order of appearance) the arteries, gray matter (GM), white matter (WM), veins and sinuses, and choroid plexus mixed with cerebrospinal fluid (CSF). The averaged rCBV, rCBF, and MTT ratios between GM and WM are in good agreement with those in the literature. Results from a patient with cerebral arteriovenous malformation (CAVM) showed distinct spatiotemporal characteristics between perfusion patterns, which allowed differentiation between pathological and nonpathological areas.

Adolescent↗
PubMed2006

The brain computer interface using flash visual evoked potential and independent component analysis.

In this study flashing stimuli, such as digits or letters, are displayed on a LCD screen to induce flash visual evoked potentials (FVEPs). The aim of the proposed interface is to generate desired strings while one stares at target stimulus one after one. To effectively extract visually-induced neural activities with superior signal-to-noise ratio, independent component analysis (ICA) is employed to decompose the measured EEG and task-related components are subsequently selected for data reconstruction. In addition, all the flickering sequences are designed to be mutually independent in order to remove the contamination induced by surrounding non-target stimuli from the ICA-recovered signals. Since FVEPs are time-locked and phase-locked to flash onsets of gazed stimulus, segmented epochs from ICA-recovered signals based on flash onsets of gazed stimulus will be sharpen after averaging whereas those based on flash onsets of non-gazed stimuli will be suppressed after averaging. The stimulus inducing the largest averaged FVEPs is identified as the gazed target and corresponding digit or letter is sent out. Five subjects were asked to gaze at each stimulus. The mean detection accuracy resulted from averaging 15 epochs was 99.7%. Another experiment was to generate a specified string '0287513694E'. The mean accuracy and information transfer rates were 83% and 23.06 bits/min, respectively.

Adult↗
PubMed2006

Estrogen rapidly modulates mustard oil-induced visceral hypersensitivity in conscious female rats: A role of CREB phosphorylation in spinal dorsal horn neurons.

This study investigated the effect of sex hormones on mustard oil (MO)-induced visceral hypersensitivity in female rats and analyzed possible involved signaling pathways. Female rats, either intact or ovariectomized (OVX), were prepared for abdominal muscle electromyography in response to colorectal distension after intracolonic instillation of MO. The effect of MO intracolonic sensitization was evaluated in intact rats, OVX rats, and OVX rats pretreated with a single injection of 17beta-estradiol (E), progesterone (P), E+P, or vehicle. cAMP-responsive element-binding protein (CREB) and phosphorylated CREB (pCREB) were detected in the superficial dorsal horn of L6 and S1 in MO or mineral oil-treated OVX rats with/without colorectal distension and estrogen replacement. The distal colorectum was removed for histological evaluation of inflammatory severity in MO-treated intact or OVX rats. The MO-treated rats had significantly higher visceromotor reflex than controls (enhanced visceral hypersensitivity), whereas OVX eliminated this hypersensitivity. After a single injection of E or E+P, the rats rapidly restored MO-induced visceral hypersensitivity within 2 h. Estrogen also rapidly induced a dose-dependent increase in pCREB expression in the superficial dorsal horn neurons in MO-treated, but not mineral oil-treated, OVX rats. The present study suggests that estrogen can rapidly modulate visceral hypersensitivity induced by MO intracolonic instillation in conscious female rats, which may involve spinal activation of the cAMP response element-mediated gene induction pathway.

Animals↗
PubMed2006

Dimensional complexity of neuromagnetic activity reduced during finger movement of greater difficulty.

OBJECTIVE: We investigated the variation in dimensionality (D2) of neuromagnetic activity over the primary sensorimotor cortex (SM1) in healthy adults performing motor tasks of different difficulty. METHODS: Magnetoencephalography (MEG) was used to record neuromagnetic activity during self-paced, brisk unimanual finger extension at a rate of 1 and 2 Hz using the index finger of the dominant and non-dominant hands in 16 healthy subjects. Motor task difficulty was rated by the relative difference in time measurement between 1 and 2 Hz finger movements of both hands. The relative difference in dimensionality of SM1 activity was calculated by subtracting the D2 value in 2 Hz movement from that in 1 Hz one within subjects. RESULTS: Simple regression analyses show a significantly negative relationship between the relative dimensional complexity and the relative motor task difficulty in the contralateral SM1 for the left- (p<0.05), but not the right- (p=0.447) hand movement. CONCLUSIONS: The present data suggest that a motor task of greater difficulty may engender a reduction of simultaneously active quasi-independent neuronal generators in the contralateral SM1 underpinned by stronger neuronal connectivity of a relatively low dimensionality. SIGNIFICANCE: The decrease in dimensional complexity of MEG activity associated with a motor task of greater difficulty gives new insights to motor control strategy.

Adult↗
PubMed2006

Gender differences in the human mirror system: a magnetoencephalography study.

The present study investigated whether the human mirror-neuron system exhibits gender differences. Neuromagenetic mu (approximately 20 Hz) oscillations were recorded over the right primary motor cortex, which reflect the mirror neuron activity, in 10 female and 10 male participants while they observed the videotaped hand actions and moving dot. In accordance with previous studies, all participants had mu suppression during the observation of hand action, indicating activation of primary motor cortex. Interestingly, the female participants displayed apparently stronger (P < 0.05) suppression for the hand action than for the moving dot whereas the men showed the opposite (P < 0.05). These findings have implications for the extreme male brain theory of autism and support the hypothesis of a dysfunctional mirror-neuron system in autism.

Adult↗
PubMed2006

An MEG study into the visual perception of apparent motion in depth.

This study investigated (1) the responses associated with the perception of motion in depth induced by a series of scale-changing paradigms, and (2) the locations of the dipoles in the brain elicited by stimuli of motion in depth and in-plane motion. The former was determined using two types of stimulation: real motion and apparent motion in scale (AMS; where two frames with size-changed patterns were presented alternately); and the latter was determined by moving a full-field checkerboard pattern forward or rightward smoothly with the same time course. The results from analyzing magnetoencephalography (MEG) component M160 to differentiate the signals of perception can be summarized as follows: (1) the neurons stimulated by apparent motion (AM) might be similar to those stimulated by a real motion, since there was no statistical difference associated with the signals at M160 and the dipole locations; (2) the perceptional signal of motion in depth seems to be more sensitive when scale-changing information is present; and (3) asymmetrical responses are present in the visual system, with responses being more sensitive to expanding stimuli than to contracting ones, and with the activity being more prominent in the right occipitotemporal area. Overall, this study indicates that the responses evoked by the stimuli causing motion in depth are allocated more to area V3a rather to area V5.

Adult↗
PubMed2006

Effects of cognitive demands on postmovement motor cortical deactivation.

Postmovement beta-rebounds induced by different intermovement intervals were investigated using magnetoencephalography in 14 healthy participants to test the hypothesis that postmovement motor cortical deactivation over the primary motor cortex depends on movement-related cognitive demands. Shorter latency and lower amplitude in postmovement beta-rebounds over the contralateral primary motor cortex were noted in the short-movement interval movement (repetitive finger lifting). Greater latency span of postmovement beta-rebounds jittering using single-trial analysis in the long-movement interval movement (discrete finger lifting) was observed. The study elucidates that the temporal interval between two adjacent movements reflecting different degrees of cognitive demands can affect postmovement motor cortical deactivation in terms of postmovement beta-rebounds latency and amplitude, and latency span of postmovement beta-rebounds jittering. Postmovement motor cortical deactivation can reflect cognitive demands in addition to motor and somatosensory processing.

Adult↗
PubMed2006

An improved spectral width Doppler method for estimating Doppler angles in flows with existence of velocity gradients.

Doppler angle (i.e., beam-to-flow angle) is an important parameter for quantitative flow measurements. With known Doppler angles, volumetric flows can be obtained by the mean flow velocity times the cross-section area of the vessel. The differences or changes between prestenotic and poststenotic volumetric flows have been quantified as an indicator for assessing the clinical severity of the stenosis. Therefore, several research groups have dedicated themselves to developing user-independent methods to determine automatically the Doppler angle. Nevertheless, most of these methods were developed for narrow ultrasound beam measurements. For small vessels, where the beam width is a significant fraction of the diameter of the vessel, the effect of velocity gradients plays an important role and should not be ignored in the Doppler angle estimations. Accordingly, this paper is concerned with a method for improving the estimation of Doppler angles from spectral width Doppler (SWD) method, but correcting for velocity-gradient broadening that may arise when the beam has a nonzero width. In our method, Doppler angles were firstly calculated by SWD and then were corrected by an artificial neural network (ANN) method to neutralize the contribution of velocity gradient broadening (VGB). This SWD and ANN conjoint method has been successfully applied to estimate Doppler angles from 50 degrees to 80 degrees for constant flows in 10 mm, 4 mm and 1 mm diameter tubes, whose mean flow velocities were 15.3, 19.9 and 25.5 cm/s, respectively, and the achieved mean absolute errors of the estimated Doppler angles were 1.46 degrees , 1.01 degrees and 1.3 degrees.

Blood Flow Velocity↗
PubMed2006

Maximum contrast beamformer for electromagnetic mapping of brain activity.

Beamforming technique can be applied to map the neuronal activities from magnetoencephalographic/electroencephalographic (MEG/EEG) recordings. One of the major difficulties of the scalar-type MEG/EEG beamformer is the determination of accurate dipole orientation, which is essential to an effective spatial filter. This paper presents a new beamforming technique which exploits a maximum contrast criterion to maximize the ratio of the neuronal activity estimated in a specified active state to the activity estimated in a control state. This criterion leads to a closed-form solution of the dipole orientation. Experiments with simulation, phantom, and finger-lifting data clearly demonstrate the effectiveness, efficiency, and accuracy of the proposed method.

Algorithms↗
PubMed2005

Modulation of spinal excitability during observation of bipedal locomotion.

This study investigated whether a mirror mechanism exists for bipedal locomotion. We employed the soleus (plantar flexor) Hoffman reflex to investigate corticospinal excitability at the spinal level during observation of bipedal locomotion. The differential amplitude modulation of the left soleus Hoffman reflex during observation of bipedal heel-stepping (plantar dorsiflexion) (324+/-53 microV), standing still (383+/-60 microV), and bipedal toe-stepping (plantar flexion) (419+/-53 microV) reached significance (P < 0.05). The observation of bipedal toe-stepping produced a greater increase in spinal excitability than the observation of bipedal heel-stepping. These findings support the suggestion that there is a mirror mechanism for bipedal locomotion and they demonstrate that spinal excitability for observation of bipedal locomotion mirrors that for execution of bipedal locomotion.

Adult↗
PubMed2005

Oscillatory characteristics of face-evoked neuromagnetic responses.

To study the oscillatory activities during face processing, we recorded magnetoencephalographic responses in 8 healthy subjects to upright and inverted human faces, and obtained the time-frequency representation by using wavelet transform. Delta to beta activities were clearly increased at 140-210 ms after stimulus onset in the bilateral occipitotemporal (OT) areas (t(7)>5.5; p<0.001), with larger power for theta, alpha and beta over the right side. Notably, more increase alpha activity for inverted than upright face condition was observed in the right OT area. Our results suggest that 4-25 Hz oscillations are involved in face information processing, and the more activation over the right OT implies the right hemisphere advantage for face perception. Moreover, the alpha activity may reflect the differential cortical demands for processing inverted and upright face images.

Adult↗
PubMed2005

Spatiotemporal brain dynamics in response to muscle stimulation.

The objective of the present study was to assess the spatiotemporal scenario of brain activity associated with sensory stimulation of the abductor pollicis brevis muscle. Spatiotemporal dipole models, using realistic individual boundary element head models, were built from somatosensory evoked potentials (SEPs; 64 Ch. EEG) to nonpainful and painful intramuscular electrostimulation (IMES) as well as to cutaneous electrostimulation delivered to the distal phalanx of the thumb. Nonpainful and painful muscle stimuli resulted in activation of the same brain regions. In temporal order, these were: the contralateral primary sensorimotor cortex, contralateral dorso-lateral premotor area (PM), bilateral operculo-insular cortices, caudal cingulate motor area (CMA), and posterior cingulate cortex/precuneus. Brain processing induced by muscle sensory input showed a characteristic pattern in contrast to cutaneous sensory input, namely: (1) no early SEP components to IMES; (2) an initial IMES component likely generated by proprioceptive input is not present for digit stimulation; (3) one source was located in the PM only for IMES. This source was unmasked by the lower stimulus intensity; (4) a source for IMES was located in the contralateral caudal CMA rather than being located in the cingulate gyrus. Cerebral sensory processing of input from the muscle involved several sensory and motor areas and likely occurs in two parallel streams subserving higher order somatosensory processing as well as sensory-motor integration. The two streams might on one hand involve sensory discrimination via SI and SII and on the other hand integration of sensory feedback for further motor processing via MI, lateral PM area, and caudal CMA.

Adult↗
PubMed2005

The effects of face spatial frequencies on cortical processing revealed by magnetoencephalography.

To study the spatial frequency (SF) effects on cortical face processing, we recorded magnetoencephalographic responses in seven healthy subjects to upright and inverted human faces. Four face types were used, including original (broad-band SF, BSF), low SF (LSF, <5 cycles/face), middle SF (MSF, 5-15 cycles/face), and high SF (HSF, >15 cycles/face) face images. Using equivalent current dipole (ECD) modeling, neuromagnetic M170 responses peaking around 160-185 ms were localized in right occipitotemporal region across subjects to BSF faces. M170 responses to LSF faces showed longer latency and smaller amplitude compared with those to BSF faces. We found no significant difference between BSF, MSF, and HSF conditions in M170 amplitude or latency. ECD locations for the four upright face conditions were close to one another, although the mean locations for MSF or HSF seemed more medial than those for BSF or LSF. Longer latencies for inverted than upright faces were observed in BSF (183.4+/-8.5 ms versus 168+/-6.9 ms, P<0.001) and LSF face conditions (223.6+/-13.1 ms versus 207.3+/-16.3 ms, P<0.01). M170 ECDs were located more medial for inverted than upright images in either BSF or LSF condition. In conclusion, the less M170 activation to LSF faces suggests that face parts information is important for early face processing. The cortical representations in right occipitotemporal region for configural and face feature processing are overlapping. Our findings on the face inversion effect suggest that inverted BSF and LSF faces may be processed as objects.

Adult↗
PubMed2005

Recognition of motor imagery electroencephalography using independent component analysis and machine classifiers.

Motor imagery electroencephalography (EEG), which embodies cortical potentials during mental simulation of left or right finger lifting tasks, can be used to provide neural input signals to activate a brain computer interface (BCI). The effectiveness of such an EEG-based BCI system relies on two indispensable components: distinguishable patterns of brain signals and accurate classifiers. This work aims to extract two reliable neural features, termed contralateral and ipsilateral rebound maps, by removing artifacts from motor imagery EEG based on independent component analysis (ICA), and to employ four classifiers to investigate the efficacy of rebound maps. Results demonstrate that, with the use of ICA, recognition rates for four classifiers (fisher linear discriminant (FLD), back-propagation neural network (BP-NN), radial-basis function neural network (RBF-NN), and support vector machine (SVM)) improved significantly, from 54%, 54%, 57% and 55% to 70.5%, 75.5%, 76.5% and 77.3%, respectively. In addition, the areas under the receiver operating characteristics (ROC) curve, which assess the quality of classification over a wide range of misclassification costs, also improved from .65, .60, .62, and .64 to .74, .76, .80 and .81, respectively.

Adult↗
PubMed2005

Changes of the neuropeptides content and gene expression in spinal cord and dorsal root ganglion after noxious colorectal distension.

Visceral pain/hypersensitivity is a cardinal symptom of functional gastrointestinal disorders. With their peripheral and central (spinal) projections, sensory neurons in the dorsal root ganglia (DRG) are the "gateway" for painful signals emanating from both somatic and visceral structures. In contrast to somatic pain, the neurochemical pathways involved in visceral pain/hypersensitivity have not been well studied. We hypothesized the neuropeptide changes in spinal cord and DRG during visceral pain would mirror similar changes in somatic nociception. Noxious (painful) colorectal distension (CRD) was done by distending a rectal balloon up to 60 mm Hg phasically for 1 h in Sprague-Dawley rats. The spinal content of calcitonin gene-related peptide (CGRP), substance P (SP), galanin and vasoactive intestinal peptide (VIP) as well as their mRNAs in DRG were measured at 0, 4 and 24 h after the CRD. Visceromotor reflex (VMR) was measured by recording the electromyogram at the abdominal muscle in response to CRD. Distal colorectum was removed for evaluating the presence of inflammation. No significant evidence of histological inflammation was seen in the colonic mucosa/submucosa after repeated CRD, which is confirmed by myeloperoxidase assay. The spinal content of CGRP and SP decreased significantly 4 h after CRD, while galanin and VIP levels increased gradually and reached highest level at 24 h (p<0.05). The mRNAs in DRG of the neuropeptides were significantly upregulated after CRD (p<0.05). VMR recording showed the rat's colon became hypersensitive 4 h after CRD, a sequence parallel to the spinal changes of CGRP and SP in timeframe. Noxious mechanical distension of the colorectum causes an acute change in the spinal levels of excitatory neurotransmitters (CGRP and SP), probably reflecting central release of these peptides from sensory neurons and contributing to the hypersensitivity following the noxious CRD. This is followed by a slower change in the levels of the inhibitory neurotransmitter galanin and VIP. Such stimulation results in significant alternation of the gene expression in DRG, reflecting the plasticity of the neuronal response. In the absence of visceral inflammation, the aforementioned neuropeptides are important mediators in the processing of visceral pain/hypersensitivity.

Animals↗
PubMed2005

Optimal check size and reversal rate to elicit pattern-reversal MEG responses.

OBJECTIVE: To determine the impact of check size and interstimulus interval (ISI) on neuromagnetic visual cortical responses. METHODS: We recorded visual evoked fields to pattern-reversal stimulation with central occlusion in ten subjects. The -100 ms magnetic activation (P100m) was analyzed by single dipole modeling. RESULTS: With 1 s ISI, P100m strengths increased as check size increased from 15' up to 120' of visual arc, and larger checks elicited less P100m activation. With 120' checks, we found no P100m attenuation as ISI decreased from 4 s to 0.16 s. P100m sources around the calcarine sulcus did not vary with check size or ISI. CONCLUSIONS: The magnitude of cortical activation during visual contrast processing is check size-dependent and the 120' checks are optimum for future studies on neuromagnetic visual cortical functions using central-occluded stimulation. The corresponding neuronal activation demonstrated a short refractory period less than 0.16 s. We also found significantly overlapping cortical representation areas for different check sizes or ISIs.

Adult↗
PubMed2005

Convulsive syncope: an unusual complication of acupuncture treatment in older patients.

Vasovagal syncope is an uncommon complication during acupuncture. However, convulsive syncope during acupuncture treatment in older individuals is seldom reported in the literature. Two older patients who experienced convulsive syncope during acupuncture treatment at Taipei Veterans Hospital, Taipei, Taiwan, from January 2000 to December 2002 are reported. These cases are instructive to acupuncturists. Although acupuncture treatment is generally safe in most situations, one needs to be cautious in delivering acupuncture to older and debilitated individuals.

Acupuncture Therapy↗