Benefits of combination of electroencephalography, short latency somatosensory evoked potentials, and transcranial Doppler techniques for confirming brain death

Objective: Optimization of combining electroencephalography (EEG), short latency somatosensory evoked potentials (SLSEP) and transcranial Doppler (TCD) techniques to diagnose brain death. Methods: One hundred and eleven patients (69 males, 42 females) from the major hospitals of Zhejiang Province were examined with portable EEG, SLSEP and TCD devices. Re-examinations occurred ≤12 h later. Results: The first examination revealed that the combination of SLSEP and EEG led to more sensitive diagnoses than the combination of SLSEP and TCD. Re-examination confirmed this and also revealed that the combination of TCD and EEG was the most sensitive. Conclusion: The results show that using multiple techniques to diagnose brain death is superior to using single method, and that the combination of SLSEP and EEG is better than other combinations.

Effect of Qiangli Dingxuan Tablet on Cerebral Hemodynamics and Brainstem Auditory Evoked Potentials in Vertigo Patients with Posterior Circulation Ischemia

OBJECTIVE: To observe the effect of Qiangli Dingxuan Tablet on cerebral hemodynamics and brainstem auditory evoked potentials in vertigo patients with posterior circulation ischemia. METHODS: A total of 120 vertigo patients with posterior circulation ischemia were randomly divided into observation group and control group. 60 patients in the control group were treated with conventional western medicine. 60 patients in the observation group were treated with Qiangli Dingxuan Tablet on the basis of the control group. After 2 weeks of treatment, the improvement of vertigo(dizziness handicap inventory(DHI), dizziness handicap inventory(DHI)), the hemodynamic index(Basilar artery blood flow velocity(BA), left vertebroarterial artery(LVA), and the average blood flow velocity of right vertebroarterial artery(RVA)) and the changes in brain stem auditory evoked potential(BAEP) of two groups were observed. And statistical analysis was conducted for the clinical efficacy and adverse reactions during treatment of two groups. RESULTS: The total effective rate of the observation group was significantly higher than that of the control group(P < 0.05). The DHI and DARS scores of the two groups were significantly lower than those before treatment(P < 0.05), and the degree of reduction was more obvious in the observation group(P < 0.05). The levels of BA, LVA and RVA in the two groups were significantly higher than those before treatment(P < 0.05), and the levels of BA, LVA and RVA in the observation group were significantly higher than those in the control group(P < 0.05). The indexes of BAEP latency I, II, III and indexes of BAEP peak latency I-III, III-V, IV were obviously lower than those before treatment(P < 0.05). Besides, the decrease of BAEP index in the observation group was significantly lower than that in the control group(P < 0.05). No adverse reactions occurred during the treatment of the two groups. CONCLUSION: Qiangli Dingxuan Tablet is able to significantly improve the cerebral hemodynamics and brainstem auditory evoked potentials of patients with PCIV, and quickly relieve vertigo. It is safe and reliable and worthy of clinical application.

BRAIN DYSFUNCTION OF PATIENTSWITH QIGONG INDUCED MENTAL DISORDERREVEALED BY EVOKED POTENTIALS RECORDING

Objective: In order to investigate the brain function of patients with Qigong induced mental disorder (QIMD), this study was carried out. Methods: Four kinds of evoked potentials, including contingent negative variation (CNV), auditory evoked potentials (AEP), visual evoked potentials (VEP), and somatosensory evoked potentials (SEP), were recorded from 12 patients with Qigong induced mental disorder.Comparison of their evoked potentials with the data from some normal controls was made. Results: The results revealed that there were 3 kinds of abnormal changes in evoked potentials of patients with QIMD that is latency prolongation, amplitude increase and amplitude decrease, as compared with normal controls. Conclusion: Brain dysfunction of patients with QIMD was confirmed. Its biological mechanism needs further studying.

Effect of Acupuncture on the Auditory Evoked Brain Stem Potential in Parkinson's Disease

Under the auditory evoked brain stem potential (ABP) examination, the latent period of V wave and the intermittent periods of III-V peak and I-V peak were significantly shortened in Parkinson's disease patients of the treatment group (N=29) after acupuncture treatment. The difference of cumulative scores in Webster's scale was also decreased in correlation analysis. The increase of dopamine in the brain and the excitability of the dopamine neurons may contribute to the therapeutic effects, in TCM terms, of subduing the pathogenic wind and tranquilizing the mind.……

A Temporal–Spatial Atlas of Peripheral Nerve Evoked Cortex Potential in Rat:A Novel Testbed to Explore the Responding Patterns of the Brain to Peripheral Nerves

Observing the dynamic progress of the brain in response to peripheral nerve stimulation as a whole is the basis for a deeper understanding of overall brain function;however,it remains a great challenge.In this work,a novel mini-invasive orthogonal recording method is developed to observe the overall evoked cortex potential(ECP)in rat brain.A typical ECP atlas with recognizable waveforms in the rat cortex corresponding to the median,ulnar,and radial nerve trunks and subdivided branches is acquired.Reproducible exciting temporal–spatial progress in the rat brain is obtained and visualized for the first time.Changes in the ECPs and exciting sequences in the cortex four months after median nerve transection are also observed.The results suggest that the brain’s response to peripheral stimulation has precise and reproducible temporal–spatial properties.This resource can serve as a testbed to explore the overall functional interaction and dynamic remodeling mechanisms between the peripheral and central nervous systems over time.

Influence of stimuli color on steady-state visual evoked potentials based BCI wheelchair control

In recent years, Brain Computer Interface (BCI) systems based on Steady-State Visual Evoked Potential (SSVEP) have received much attention. This study tries to develop a SSVEP based BCI system that can control a wheelchair prototype in five different positions including stop position. In this study four different flickering frequencies in low frequency region were used to elicit the SSVEPs and were displayed on a Liquid Crystal Display (LCD) monitor using Lab-VIEW. Four stimuli colors, green, red, blue and violet were used to investigate the color influence in SSVEPs. The Electroencephalogram (EEG) signals recorded from the occipital region were segmented into 1 second window and features were extracted by using Fast Fourier Transform (FFT). One-Against-All (OAA), a popular strategy for multiclass SVM, is used to classify SSVEP signals. During stimuli color comparison SSVEP with violet color showed higher accuracy than that with green, red and blue stimuli.

Effect of Acupuncturing Houxi（S13）and Shenmen（HT7）in Trealing Cerebral Traumatio Dementia

Sixty-two cerebral traumatic patients were randomly divided into two groups: acupuncturegroup (32 cases) and physiotherapy group (30 cases) . The changes of mini-mental status examination(MMSE) scores and auditory evoked potential P300 were observed bofore and aiter treatment. Results: themarkedly effective rate and the total effective rate of the acupuncture group were 46. 9% and 81 . 3% respec-tively, which were significantly higher than that of 10. 0% and 30. 0% of the physiottierapy group (P < 0.01 ) . It was found that after treatment the above-mentioned indexes in the acupuncture group changed signifi-cantly (P < 0 . 05 ￣0. 001 ) , while in the physiotherapy group they were not(P >0. 05) . The therapeutic ef-fect in acupunctrue group was better than that in physiotherapy group (P< 0 . 001 ) . The results confirmed thatthe cognitive function of cerebral traumatic dementia patients was enhanced effectively after acupuncturingHouxi (S13 ) and Shenmen (HT7) .

Motor imagery training induces changes in brain neural networks in stroke patients

Motor imagery is the mental representation of an action without overt movement or muscle activation. However, the effects of motor imagery on stroke-induced hand dysfunction and brain neural networks are still unknown. We conducted a randomized controlled trial in the China Rehabilitation Research Center. Twenty stroke patients, including 13 males and 7 females, 32–51 years old, were recruited and randomly assigned to the traditional rehabilitation treatment group（PP group, n = 10） or the motor imagery training combined with traditional rehabilitation treatment group（MP group, n = 10）. All patients received rehabilitation training once a day, 45 minutes per session, five times per week, for 4 consecutive weeks. In the MP group, motor imagery training was performed for 45 minutes after traditional rehabilitation training, daily. Action Research Arm Test and the Fugl-Meyer Assessment of the upper extremity were used to evaluate hand functions before and after treatment. Transcranial magnetic stimulation was used to analyze motor evoked potentials in the affected extremity. Diffusion tensor imaging was used to assess changes in brain neural networks. Compared with the PP group, the MP group showed better recovery of hand function, higher amplitude of the motor evoked potential in the abductor pollicis brevis, greater fractional anisotropy of the right dorsal pathway, and an increase in the fractional anisotropy of the bilateral dorsal pathway. Our findings indicate that 4 weeks of motor imagery training combined with traditional rehabilitation treatment improves hand function in stroke patients by enhancing the dorsal pathway. This trial has been registered with the Chinese Clinical Trial Registry（registration number： Chi CTR-OCH-12002238）.

Prognosis in prolonged coma patients with diffuse axonal injury assessed by somatosensory evoked potential

A total of 43 prolonged coma patients with diffuse axonal injury received the somatosensory evoked potential examination one month after injury in the First Affiliated Hospital, School of Medicine, Zhejiang University in China. Somatosensory evoked potentials were graded as normal, abnormal or absent （grades I-III） according to N20 amplitude and central conduction time. The outcome in patients with grade III somatosensory evoked potential was in each case unfavorable. The prognostic accuracy of grade III somatosensory evoked potential for unfavorable and non-awakening outcome was 100% and 80%, respectively. The prognostic accuracy of grade I somatosensory evoked potential for favorable and wakening outcome was 86% and 100%, respectively. These results suggest that somatosensory evoked potential grade is closely correlated with coma severity and degree of recovery. Somatosensory evoked potential is a valuable diagnostic tool to assess prognosis in prolonged coma patients with diffuse axonal injury.

Collagen/heparan sulfate porous scaffolds loaded with neural stem cells improve neurological function in a rat model of traumatic brain injury

One reason for the poor therapeutic effects of stem cell transplantation in traumatic brain injury is that exogenous neural stem cells cannot effectively migrate to the local injury site,resulting in poor adhesion and proliferation of neural stem cells at the injured area.To enhance the targeted delivery of exogenous stem cells to the injury site,cell therapy combined with neural tissue engineering technology is expected to become a new strategy for treating traumatic brain injury.Collagen/heparan sulfate porous scaffolds,prepared using a freeze-drying method,have stable physical and chemical properties.These scaffolds also have good cell biocompatibility because of their high porosity,which is suitable for the proliferation and migration of neural stem cells.In the present study,collagen/heparan sulfate porous scaffolds loaded with neural stem cells were used to treat a rat model of traumatic brain injury,which was established using the controlled cortical impact method.At 2 months after the implantation of collagen/heparan sulfate porous scaffolds loaded with neural stem cells,there was significantly improved regeneration of neurons,nerve fibers,synapses,and myelin sheaths in the injured brain tissue.Furthermore,brain edema and cell apoptosis were significantly reduced,and rat motor and cognitive functions were markedly recovered.These findings suggest that the novel collagen/heparan sulfate porous scaffold loaded with neural stem cells can improve neurological function in a rat model of traumatic brain injury.This study was approved by the Institutional Ethics Committee of Characteristic Medical Center of Chinese People’s Armed Police Force,China(approval No.2017-0007.2)on February 10,2019.

Cortical evoked potential changes in a rat model of acute ischemic stroke Detection of somatosensory evoked potential and motor evoked potential

BACKGROUND： Studies have shown that latency changes of some elements in a somatosensory evoked potential （SEP） and motor evoked potential （MEP） can reflect electrical activity of cerebral cortical neurons and conduction of white matter nerve fibers. However, there is a paucity of information regarding the dynamic observation of SEP and MEP following cerebral ischemic injury. OBJECTIVE： To explore SEP and MEP changes following acute ischemic stroke, and investigate the role of evoked potentials in monitoring brain function in stroke. DESIGN, TIME AND SETTING： A randomized, controlled, animal experiment was performed at the Chongqing Key Laboratory of Neurology, Affiliated Hospital of Chongqing Medical University from September 2007 to August 2008. MATERIALS＂ Hydrogen blood flow detector was purchased from Soochow University Medical Instrument Co., China, and Power lab system was purchased from AD Instruments, Inc., USA. METHODS A total of 36 healthy, adult, male, Sprague Dawley rats were randomly assigned to four groups （n = 9）, including three ischemia groups （12, 24 and 72 hours of ischemia） and a sham-surgery group. The rat model of acute ischemic stroke was established by middle cerebral artery occlusion （MCAO） in the left hemisphere. MAIN OUTCOME MEASURES＂ SEP and MEP of the left limbs were detected, and cerebral blood flow was measured by the hydrogen cleaning method. RESULTS： The latency of positive wave 1 （P1）, negative wave 1 （N1） and positive wave 2 （P2） waves in SEP, and latency of negative wave 1,2 （N1, N2） waves in MEP were significantly prolonged with increasing ischemic duration following MCAO （P 〈 0.01）, but cerebral blood flow was significantly decreased （P 〈 0.05, or P 〈 0.01）. CONLUSION： Ischemic stroke prolongs the latency of SEP waves （P1, N1, P2） and MEP waves （N1, N2）, and cerebral cortical evoked potential may correlate with cerebral blood flow changes. This indicates that SEP and MEP can be used to evaluate brain function following acute ischemic stroke.

Electroencephalogram and evoked potential parameters examined in Chinese mild head injury patients for forensic medicine

Objective To evaluate the usefulness of quantitative electroencephalogram （QEEG）, flash visual evoked potential （F-VEP） and auditory brainstem responses （ABR） as indicators of general neurological status. Methods Comparison was conducted on healthy controls （N=30） and patients with brain concussion （N=60） within 24 h after traumatic brain injury. Follow-up study of patient group was completed with the same standard paradigm 3 months later. All participants were recorded in multi-modality related potential testing in both early and late concussion at the same clinical setting. Glasgow coma scale, CT scanning, and physical examinations of neuro-psychological function, optic and auditory nervous system were performed before electroencephalogram （EEG） and evoked potential （EEG-EP） testing. Any participants showed abnormal changes of clinical examinations were excluded from the study. Average power of frequency spectrum and power ratios were selected for QEEG testing, and latency and amplitude of F-VEP and ABR were recorded. Results Between patients and normal controls, the results indicated： （1） Highly significance （P 〈 0.01） in average power of α1 and power ratios of θ/α1, 0/α2, α1/α2 of EEG recording; （2） N70-P 100 amplitude of F-VEP in significant difference at early brain concussion; and （3） apparent prolongation of Ⅰ～Ⅲ inter-peak latency of ABR appeared in some individuals at early stage after concussion. The follow-up study showed that some patients with concussion were also afflicted with characteristic changes of EEG components for both increments of α1 average power and θ/α2 power ratio after 3 months recording. Conclusion EEG testing has been shown to be more effective and sensitive than evoked potential tests alone on detecting functional state of patients with mild traumatic brain injury （MTBI）. Increments of α1 average power and θ/α2 power ratio are the sensitive EEG parameters to determining early concussion and evaluating outcome of postconcussion symptoms （PCS）. Follow-up study associated with persistent PCS may be consistent with the postulate of substantial biological, rather than psychological origin. The study suggests that combination of EEG and EP parameters can contribute to the evaluation of brain function as a whole for clinical and forensic applications.

Changes of evoked potential and expression of nestin in subventricular zones in rats after focal cerebral ischemia

Objective： To study the characteristics of latency of somatosensory evoked potential （SEP） and motor evoked potential （MEP） and the expression of nestin in subventricular zones （SVZ） after persistent focal cerebral ischemia in rats. Methods： The model of cerebral ischemia in rats was made by middle cerebral artery occlusion （MCAO）. All animals of ischemia were sacrificed after 12 h, 1 d, 3 d, 7 d, and 14 d to observe the changes of latency of SEP and MEP and to detect the expression of nestin, with an immunohistochemical approach. Results： The latencies of P1 （positive wave 1）, N1 （negative wave 1） and P2 （positive wave 2） in SEP were significantly prolonged after MCAO. The latencies of N1 and N2 waves in MEP were postponed gradually and no statistical difference of latency of N1 wave was found in rats at 7 d and 14 d after MCAO. The expression of nestin increased at 12 h, and showed a significant augmentation at 3 d and peaked at 7 d, then declined slightly at 14 d after MCAO. Conclusion： The cerebral ischemia prolonged the latency of EP waves and the expression of nestin was up-regulated and reached the peak at 7 d, showing the ischemia induced the proliferation of nervous stem cells. The SEP and MEP may evaluate the proliferation in SVZ after brain ischemia.

Formal Auditory Training with Individuals after Traumatic Brain Injury

Purpose: Establishing the effects of a formal auditory training program on individuals, after a traumatic brain injury by means of behavioral and electrophysiological tests. Study Design: Longitudinal study. Setting: Study conducted at the electrophysiology clinic of the Federal University of S&#227;o Paulo. Patients: Nine individuals with normal hearing, 20 to 37 years old, who were exposed to severe traumatic brain injury (score of 3 - 8 on the Glasgow Coma Scale upon hospital admission), 6 - 24 months earlier (11 months on average) and had imaging tests showing diffuse axonal injury with or without associated focal lesion. Intervention(s): subjected to a formal auditory training program in an acoustic booth involving eight 45-minute sessions aiming at training the auditory temporal order judgment (frequency and duration of sounds), auditory closure, and figure-ground separation skills for verbal and nonverbal sounds in monotic and dichotic listening tasks. The sessions and activities, in each session, were organized in increasing order of complexity to challenge the auditory system. In order to establish the efficacy of the auditory training, all participants were subjected to behavioral and electrophysiological assessments of the auditory processing, before and after the formal auditory training. Results: On the electrophysiological assessment, the absolute latencies of waves III and V, and of interpeak interval I-V decreased after the auditory training. However, the P300 did not exhibit a significant difference in either the latency or the amplitude parameters. Regarding the behavioral assessment of the auditory processing, it was verified that adequacy of the auditory figure-ground skills for verbal sounds, and the temporal order judging skills. Conclusions: individuals with diffuse axonal injury following a severe traumatic brain injury exhibited an improvement of central auditory processing after formal auditory training, as manifested on electrophysiological and behavioral assessments.

Functional near-infrared spectroscopy can detect low-frequency hemodynamic oscillations in the prefrontal cortex during steady-state visual evoked potentialinducing periodic facial expression stimuli presentation

Brain oscillations are vital to cognitive functions,while disrupted oscillatory activity is linked to various brain disorders.Although high-frequency neural oscillations(>1 Hz)have been extensively studied in cognition,the neural mechanisms underlying low-frequency hemodynamic oscillations(LFHO)<1 Hz have not yet been fully explored.One way to examine oscillatory neural dynamics is to use a facial expression(FE)paradigm to induce steady-state visual evoked potentials(SSVEPs),which has been used in electroencephalography studies of high-frequency brain oscillation activity.In this study,LFHO during SSVEP-inducing periodic flickering stimuli presentation were inspected using functional near-infrared spectroscopy(fNIRS),in which hemodynamic responses in the prefrontal cortex were recorded while participants were passively viewing dynamic FEs flickering at 0.2 Hz.The fast Fourier analysis results demonstrated that the power exhibited monochronic peaks at 0.2 Hz across all channels,indicating that the periodic events successfully elicited LFHO in the prefrontal cortex.More importantly,measurement of LFHO can effectively distinguish the brain activation difference between different cognitive conditions,with happy FE presentation showing greater LFHO power than neutral FE presentation.These results demonstrate that stimuli flashing at a given frequency can induce LFHO in the prefrontal cortex,which provides new insights into the cognitive mechanisms involved in slow oscillation.

基于PSD特征的FBCCA脑电信号识别方法

当前基于稳态视觉诱发电位(steady-state visual evoked potential,SSVEP)的脑机接口(brain-computer interfaces,BCIs)使用的都是单一识别算法,针对不同时间长度的识别准确率较低。提出了一种基于滤波器组的典型相关分析(filter bank canonical correlation analysis,FBCCA)与功率谱密度(power spectral density,PSD)分析相结合的SSVEP识别算法,可以提高SSVEP识别的普适性与准确率。该方法使用FBCCA寻找高相似度的参考频率信号,再通过多组PSD分析来锁定最终的响应频率,完成频率识别。该方法无需经过训练就能得到较高的识别准确率。实验结果表明:在刺激时长为1 s时,该方法能达到86.61%的准确率,比PSD分析方法提升了5.44%,比典型相关性分析方法(canonical correlation analysis,CCA)提升了10.38%的准确率,比FBCCA提升了8.86%的准确率。

混合现实场景下结合SSVEP与眼动追踪的脑控机械臂系统

针对混合现实场景下脑控机械臂系统交互性差、指令集小的问题,设计了一种结合稳态视觉诱发电位(SSVEP)和眼动追踪技术的混合现实脑控机械臂系统。该系统通过眼动追踪技术实现目标区域的初选,而SSVEP信号则被用于在初选区域内识别最终的目标指令。在不增加刺激类别数量的前提下扩大了指令集,并根据受试者的视线停留区域实现异步控制。离线实验结果表明,在使用相同刺激类别数量的情况下,增加视觉刺激目标数量不会对分类准确率产生显著影响。通过在线实验验证了系统的适用性,相较于使用单一SSVEP范式的机械臂控制系统,所提出的系统具有更好的交互性和更大的指令集。

基于CCA融合FFT的SSVEP脑机接口分类算法

为解决多目标刺激范式的稳态视觉诱发电位脑电信号识别准确率低和信息传输率低的问题,提出了一种快速傅里叶变换同典型相关分析相结合的方法,通过快速傅里叶变换将信号训练成对应频率的训练模板,并作为参考信号与实时采集的信号进行典型相关分析来计算频率的识别准确率。6名受试者参与并完成了180组实验,在时间窗口长度为1.5 s的条件下,基于快速傅里叶变换-典型相关分析的稳态视觉诱发电位信号识别算法的平均识别准确率为93.98%,比典型相关分析算法提升了14.75%,信息传输率为62.30 bit·min^(-1),比典型相关分析算法提升了55.63%。实验结果表明,快速傅里叶变换-典型相关分析算法性能更优。

电针上肢穴位对运动皮层躯干脑区皮质脊髓兴奋性的影响

目的观察电针上肢穴位对健康受试者初级运动皮层(primary motor cortex,M1)躯干脑区皮质脊髓兴奋性的影响。方法纳入15名健康受试者,采用交叉设计。试验一观察电针上肢穴位对竖脊肌(erector spinae,ES)皮质脊髓兴奋性的影响,受试者随机先后进入3组试验,A组电针合谷穴,B组电针孔最穴,C组假针合谷穴。运用经颅磁刺激,检测干预前后对侧M1第一骨间背侧肌、桡侧腕屈肌及ES的运动诱发电位(motor evoked potentials,MEPs)的波幅和潜伏期,ES的MEPs波幅升高者进入试验二。试验二为抑制背侧前运动皮层(premotor cortex,PMd)后电针上肢穴位对ES的皮质脊髓兴奋性的作用研究,受试者随机先后进入两组试验,D组采用抑制PMd配合电针合谷穴干预,E组采用抑制PMd配合电针孔最穴干预。观察并比较两组对侧M1上肢脑区和躯干脑区MEPs的波幅和潜伏期。结果A组和B组干预后上肢脑区及躯干脑区MEPs总波幅均较同组干预前显著增加(P<0.001,P<0.01)。A组干预后上肢脑区及躯干脑区MEPs总波幅均明显高于C组,B组干预后仅躯干脑区MEPs总波幅明显高于C组,差异均具有统计学意义(P<0.001)。D组干预后上肢脑区最佳刺激点MEPs平均波幅及总波幅较同组干预前均显著增加(P<0.05)。D组和E组干预前后躯干脑区最佳刺激点的MEPs平均波幅及总波幅比较,差异也均无统计学意义(P>0.05)。结论生理状况下,电针合谷、孔最穴均可增强ES的皮质脊髓兴奋性,二者之间无明显差异,PMd可能参与其过程。

397例听神经瘤听力特征分析

目的 分析听神经瘤患者听力学特征,为筛查听神经瘤提供参考依据。方法 回顾性分析2019年8月—2022年4月诊治的397例单侧听神经瘤患者临床资料,所有患者均行纯音测听、声导抗测试、言语识别率(SDS)、畸变产物耳声发射(DPOAE)、听性脑干诱发电位(ABR)和颅脑增强MRI。结果 以典型症状就诊者312例,非典型症状就诊者85例。以突发性聋就诊者25例;患耳听力正常者54例,包含大型甚至特大型肿瘤,99例全聋者亦包含内听道和中型肿瘤。5例全聋者言语识别能力未完全消失。DPOAE一致型245例,耳蜗型72例,蜗后型79例。ABR阳性率98.0%(389/397),8例ABR波形正常者中3例为双侧非对称听力损失。结论 非典型症状就诊者占比21.4%,以突发性聋就诊、听力正常或ABR正常者不能排除听神经瘤;DPOAE和ABR可作为筛查听神经瘤的重要检查方法。