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Shouyan Wang

Publications and source records attributed to Shouyan Wang.

12 recordsLinked to original sources
PubMed2006

Digitised spirography as an evaluation tool for intention tremor in multiple sclerosis.

This study investigated validity and reliability of digitised circle and square spiral drawing for quantifying intention tremor severity and related disability in patients with multiple sclerosis (MS). The tremor amplitude was measured as the standard deviation of the drawing velocity of the arm in the radial and tangential direction for circle spiral drawing, and in the horizontal and vertical direction for square spiral drawing. Results were compared with those of MS patients without tremor and healthy controls, and correlated with clinical assessments of tremor severity and arm functionality including Fahn's tremor rating scale, Test d'Evaluation des Membres supérieurs des Personnes Agées (TEMPA) and the nine-hole-peg test to examine validity. Comparison of patient's performance between four repeated trials examined short-term test-retest reliability. All digitised spirography variables discriminated between the MS-tremor and both MS-no-tremor and healthy control groups. Validity was also shown by high spearman correlation coefficients between spirography variables and clinical ratings. Tremor appeared to be most profound in the radial and vertical direction during circle and square spiral drawing, respectively. The consistency and high correlations between four repeated executions indicated short-term test-retest reliability. We conclude that the digitised spirography provide a useful instrumentation for quantifying MS intention tremor.

Adult↗
PubMed2006

Involvement of human basal ganglia in offline feedback control of voluntary movement.

Practice makes perfect, but the neural substrates of trial-to-trial learning in motor tasks remain unclear. There is some evidence that the basal ganglia process feedback-related information to modify learning in essentially cognitive tasks , but the evidence that these key motor structures are involved in offline feedback-related improvement of performance in motor tasks is paradoxically limited. Lesion studies in adult zebra finches suggest that the avian basal ganglia are involved in the transmission or production of an error signal during song . However, patients with Huntington's disease, in which there is prominent basal ganglia dysfunction, are not impaired in error-dependent modulation of future trial performance . By directly recording from the subthalamic nucleus in patients with Parkinson's disease, we demonstrate that this nucleus processes error in trial performance at short latency. Local evoked activity is greatest in response to smallest errors and influences the programming of subsequent movements. Accordingly, motor parameters are least likely to change after the greatest evoked responses so that accurately performed trials tend to precede other accurate trials. This relationship is disrupted by electrical stimulation of the nucleus at high frequency. Thus, the human subthalamic nucleus is involved in feedback-based learning.

Aged↗
PubMed2006

Identifying cardiorespiratory neurocircuitry involved in central command during exercise in humans.

For almost one hundred years, the exact role of human brain structures controlling the cardiorespiratory response to exercise ('central command') has been sought. Animal experiments and functional imaging studies have provided clues, but the underlying electrophysiological activity of proposed relevant neural sites in humans has never been measured. In this study, local field potentials were directly recorded in a number of 'deep' brain nuclei during an exercise task designed to dissociate the exercise from peripheral feedback mechanisms. Several patient groups had electrodes implanted sterotaxically for the treatment of movement disorder or chronic pain. Fast Fourier transform analysis was applied to the neurograms to identify the power of fundamental spectral frequencies. Anticipation of exercise resulted in increases in heart rate, blood pressure and ventilation. The greatest neural changes were found in the periaqueductal grey area (PAG) where anticipation of exercise was accompanied by an increase of 43% in the power of the 12-25 Hz frequency band (P = 0.007). Exercise increased the activity by 87% compared to rest (P = 0.006). Changes were also seen in the 60-90 Hz band when anticipation or exercise increased power by 32% (P = 0.006) and 109% (P < 0.001), respectively. In the subthalamic nucleus there was a reduction in the power of the beta frequency during both anticipation (7.6 +/- 0.68% P = 0.001) and exercise (17.3 +/- 0.96% P < 0.001), whereas an increase was seen with exercise only at higher frequencies (93 +/- 1.8% P = 0.007). No significant changes were seen in the globus pallidus during anticipation of exercise. We provide direct electrophysiological evidence highlighting the PAG as an important subcortical area in the neural circuitry of the cardiorespiratory response to exercise, since stimulation of this structure is known to alter blood pressure in awake humans.

Adult↗
PubMed2006

Stimulating the human midbrain to reveal the link between pain and blood pressure.

The periaqueductal grey area (PAG) in the midbrain is an important area for both cardiovascular control and modulation of pain. However, the precise relationship between pain and blood pressure is unknown. We prospectively studied 16 patients undergoing deep brain stimulation of the rostral PAG for chronic pain. Pre-operatively, post-operatively, and at 1 year, pain scores were assessed using both visual analogue scores and the McGill Pain Questionnaire. Patients were tested post-operatively to determine whether electrical stimulation of the PAG would modulate blood pressure. We found that the degree of analgesia induced by deep brain stimulation of the rostral PAG in man is related to the magnitude of reduction in arterial blood pressure. We found that this relationship is linear and is related to reduced activity of the sympathetic nervous system. Thus stimulation of the PAG may partly control pain by reducing sympathetic activity as predicted by William James over a century ago.

Adult↗
PubMed2006

Physiological and harmonic components in neural and muscular coherence in Parkinsonian tremor.

OBJECTIVE: To differentiate physiological from harmonic components in coherence analysis of the tremor-related neural and muscular signals by comparing power, cross-power and coherence spectra. METHODS: Influences of waveform, burst-width and additional noise on generating harmonic peaks in the power, cross-power and coherence spectra were studied using simulated signals. The local field potentials (LFPs) of the subthalamic nucleus (STN) and the EMGs of the contralateral forearm muscles in PD patients with rest tremor were analysed. RESULTS: (1) Waveform had significant effect on generating harmonics; (2) noise significantly decreased the coherence values in a frequency-dependent fashion; and (3) cross-spectrum showed high resistance to harmonics. Among six examples of paired LFP-EMG signals, significant coherence appeared at the tremor frequency only, both the tremor and double tremor frequencies and the double-tremor frequency only. CONCLUSIONS: In coherence analysis of neural and muscular signals, distortion in waveform generates significant harmonic peaks in the coherence spectra and the coherence values of both physiological and harmonic components are modulated by extra noise or non-tremor related activity. SIGNIFICANCE: The physiological or harmonic nature of a coherence peak at the double tremor frequency may be differentiated when the coherence spectra are compared with the power and in particular the cross-power spectra.

Electric Stimulation↗
PubMed2006

The physiologically modulated electrode potentials at the depth electrode-brain interface in humans.

To study the modulated electrical potential specifically related to the electrode-brain interface (EBI) in deep brain stimulation (DBS) under physiological condition, we quantitatively identified the physiologically modulated electrode potentials by decomposing the local field potentials (LFPs) recorded from 11 patients (18 electrodes in four different brain regions) who underwent DBS, and correlated them with simultaneously recorded physiological signals of blood pressure (BP) and respiration. Results showed that electrode potentials were modulated by BP and respiration and could be detected as a specific component of the compound LFP signals with a mean (+/-S.D.) amplitude of 6.9+/-1.7 microV. The detection rate and amplitude of the modulated electrode potentials were independent from brain regions and neurological disorders. The current approach can be used to study the changes in properties of the EBI under physiological condition and to investigate the effects of the EBI on the 'crossing' current of either the neural signals to be recorded or the electrical pulses for neurostimulation.

Blood Pressure↗
PubMed2006

Different mechanisms may generate sustained hypertonic and rhythmic bursting muscle activity in idiopathic dystonia.

Despite that deep brain stimulation (DBS) of the globus pallidus internus (GPi) is emerging as the favored intervention for patients with medically intractable dystonia, the pathophysiological mechanisms of dystonia are largely unclear. In eight patients with primary dystonia who were treated with bilateral chronic pallidal stimulation, we correlated symptom-related electromyogram (EMG) activity of the most affected muscles with the local field potentials (LFPs) recorded from the globus pallidus electrodes. In 5 dystonic patients with mobile involuntary movements, rhythmic EMG bursts in the contralateral muscles were coherent with the oscillations in the pallidal LFPs at the burst frequency. In contrast, no significant coherence was seen between EMG and LFPs either for the sustained activity separated out from the compound EMGs in those 5 cases, or in the EMGs in 3 other cases without mobile involuntary movements and rhythmic EMG bursts. In comparison with the resting condition, in both active and passive movements, significant modulation in the GPi LFPs was seen in the range of 8-16 Hz. The finding of significant coherence between GPi oscillations and rhythmic EMG bursts but not sustained tonic EMG activity suggests that the synchronized pallidal activity may be directly related to the rhythmic involuntary movements. In contrast, the sustained hypertonic muscle activity may be represented by less synchronized activity in the pallidum. Thus, the pallidum may play different roles in generating different components of the dystonic symptom complex.

Adult↗
PubMed2006

Controlling the heart via the brain: a potential new therapy for orthostatic hypotension.

OBJECTIVE: Electrical stimulation of the midbrain is known to influence blood pressure in animals. In humans, it is used for the treatment of chronic neuropathic pain. Our aim was to assess whether orthostatic hypotension can be successfully treated with deep brain stimulation of the periventricular/periaqueductal gray areas in humans. METHODS: We recruited 11 patients who had chronic neuropathic pain and who had undergone implantation of a deep brain stimulator in the periventricular/periaqueductal gray areas. Patients were divided into three groups depending on whether they had orthostatic hypotension (one patient), mild orthostatic intolerance (five patients), or no orthostatic intolerance (five patients). Postoperatively, we continuously recorded blood pressure and heart rate with stimulation off and on and in both sitting and standing positions. From these values, we derived the blood pressure changing rate. Using autoregressive modeling techniques, we calculated changes in low- and high-frequency power spectra of heart rate and baroreflex sensitivity. RESULTS: Electrical stimulation reduced the decrease in systolic blood pressure on standing from 28.2 to 11.1% in one patient with orthostatic hypotension (P < 0.001). In the mild orthostatic intolerance group, an initial drop in systolic blood pressure of 15.4% was completely reversed (P < 0.001). There were no side effects in the remaining group. These changes were accompanied by increases in the blood pressure changing rate, the baroreflex sensitivity, and the baseline (sitting) low-frequency power of the RR interval, but not the high-frequency power. CONCLUSION: Electrical stimulation of the human periventricular/periaqueductal gray areas can reverse orthostatic hypotension. The cause seems to be an increase in sympathetic outflow and in baroreflex sensitivity. This has important implications for future therapies.

Adult↗
PubMed2006

Use of surface electromyography to assess and select patients with idiopathic dystonia for bilateral pallidal stimulation.

OBJECT: The object of this study was to identify a preoperative physiological index by using surface electromyography (EMG) signals that would correlate with clinical outcome in dystonic patients following bilateral pallidal stimulation. METHODS: In 14 patients with spasmodic torticollis, generalized dystonia, and myoclonic dystonia, surface EMG signals were recorded from the most affected muscle groups. Although the dystonia affected different body segments, the EMG signals in all patients could be decomposed into bursting and sustained components. Subsequently, a ratio of the EMG amplitude was calculated between the two components and then correlated with clinical outcome. Patients who experienced rapid improvement following bilateral pallidal stimulation had a significantly higher EMG ratio compared with those who did not. Furthermore, a significant correlation was found between the EMG ratio and clinical improvement during the 12-month period following pallidal stimulation. CONCLUSIONS: The authors concluded that surface EMG studies could be used to predict the clinical outcome of and to select patients for pallidal stimulation for dystonia.

Adult↗
PubMed2005

Deep brain stimulation can regulate arterial blood pressure in awake humans.

The periaqueductal grey matter is known to play a role in cardiovascular control in animals. Cardiovascular responses to electrical stimulation of the periventricular/periaqueductal grey matter were measured in 15 awake human study participants following implantation of deep brain stimulating electrodes for treatment of chronic pain. We found that stimulation of the ventral periventricular/periaqueductal grey matter caused a mean reduction in systolic blood pressure of 14.2+/-3.6 mmHg in seven patients and stimulation of the dorsal periventricular/periaqueductal grey matter caused a mean increase of 16.7+/-5.9 mmHg in six patients. A comparison between ventral and dorsal electrodes demonstrated significant differences (P<0.05). These changes were accompanied by analogous changes in diastolic blood pressure, pulse pressure, maximum dP/dt but not in the time interval between each R wave on the electrocardiogram.

Adult↗
PubMedDate not supplied

The direction of oscillation in spiral drawings can be used to differentiate distal and proximal arm tremor.

The assessment of the extent of involvement of the distal and proximal joints in a complex arm tremor is important clinically, as tremor generated around the distal and proximal arm joints can be differentially alleviated by surgical intervention to the thalamic and subthalamic targets, respectively. We observed that the tremor present in spiral drawings shows a diagonal directional preference. We hypothesized that the directional preference of tremor within spiral drawings could be related to the involvement of different arm joints. In this study, we tested this hypothesis by: (1) studying simulated tremulous drawings performed by healthy subjects with the joints selectively restrained; (2) recording surface EMGs from the forearm extensor and deltoid muscles during drawing; and (3) mathematical modelling the kinematics of the arm in 2D drawings. Our data showed that a "main diagonal" axis of orientation of the tremor along the orientation of the forearm indicates a predominantly proximal tremor driven by the shoulder, and a "cross diagonal" axis of orientation of tremor (i.e. perpendicular to the forearm) indicates that the tremor is predominantly distal and driven by the elbow or wrist. We conclude that the spiral drawing task can be used as an objective and quantitative method for differentiating the involvement of the proximal and distal arm joints in complex arm tremors.

Activity Cycles↗