Objective To analyze the symmetry of multifocal visual evoked potential (mfVEP) between both eyes in normal subjects. Methods The monocular mfVEP of both eyes in thirty-six normal subjects (72 eyes) was tested with VERIS Science 4.0. The stimulus was the pattern reversal dart array consisted of 60 sectors each included 16 black-white reverse patterns. The visual stimulation was controlled by the binary pseudo-random m-sequences and subtended approximately 25 degrees. Results There existed no statistically significant difference of P1 latencies and amplitudes between correspondent quadrant visual field of both eyes. The data difference of the ipsilateral quadrant visual fields was greater than those of the correspondent quadrant visual field. The comparison among four quadrant visual fields in right eye or left eye each showed that there was statistically significant difference of P1 latencies between the superionasal quadrant visual field and inferiotemporal or inferionasal quadrant visual fields. Conclusions The symmetry of normal mfVEP is more dominant in retina than that in visual cortex. (Chin J Ocul Fundus Dis, 2006, 22: 42-44)
Spinal cord stimulation (SCS) for pain is usually implanted as an open loop system using unchanged parameters. To avoid the under and over stimulation caused by lead migration, evoked compound action potentials (ECAP) is used as feedback signal to change the stimulating parameters. This study established a simulation model of ECAP recording to investigate the relationship between ECAP component and dorsal column (DC) fiber recruitment. Finite element model of SCS and multi-compartment model of sensory fiber were coupled to calculate the single fiber action potential (SFAP) caused by single fiber in different spinal cord regions. The synthetized ECAP, superimposition of SFAP, could be considered as an index of DC fiber excitation degree, because the position of crests and amplitude of ECAP corresponds to different fiber diameters. When 10% or less DC fibers were excited, the crests corresponded to fibers with large diameters. When 20% or more DC fibers were excited, ECAP showed a slow conduction crest, which corresponded to fibers with small diameters. The amplitude of this slow conduction crest increased as the stimulating intensity increased while the amplitude of the fast conduction crest almost remained unchanged. Therefore, the simulated ECAP signal in this paper could be used to evaluate the degree of excitation of DC fibers. This SCS-ECAP model may provide theoretical basis for future clinical application of close loop SCS base on ECAP.
OBJECTIVE: To investigate the characteristics and the pathologic classification of electrical-injury nerve using somatosensory evoked potential(SEP) technique. METHODS: SEP were detected and evaluated in 12 cases with electrical-injury nerve during operation, electrical stimulation was commenced from distal side of nerve where the structure of nerve looks normal under operating microscope, up to proximal side until evoking out a stable SEP predeterminate virtual value. Pathological examination and the following functional evaluation were compared with the values of SEP. RESULTS: At the site of nerve looking normal under operating microscope, perineurium appears normal or slightly thicken. But there are obvious fibrosis and fibrotic proliferation between fascicular and intrafascicular. Vessel plexus is not seen. At SEP stabilizely evoked site, nervous construction is normal, there are visible interfascicular vessel plexus and connective tissue appears loose. Comparing SEP values with pathological section, amplitude and latency of SEP is positively correlative with the quality of nerve. Eight cases repaired with SEP technique to select the anastomosis site for nerve transplantation were followed up, two-point discrimination reached grade III (America hand surgery association criterion) within 62.5% cases. CONCLUSION: SEP technique is valuable method for functional evaluation of electrical- injury nerve which has a complicated pathology. The pathology of electrical-injury nerve can be classified into 4 types, type A: fibrosis of nerve; type B: nerve looking normal under operation microscope, perineurium appears thicken, and there are obvious fibrosis and fibrotic proliferation between fascicular and intrafascicular, vessel plexus is rarely to see; type C: nerve looks normal, lymphocyte infiltration exists and it is obvious that there are many physalis-like, retrogressive construction in the section; type D: nervous construction is normal, there are visible interfascicular vessel plexus, and connective tissue appears loose, SEP always can be stably evoked.
ObjectiveTo evaluate the differences of visual evoked potentials (amplitudes and latency) between cerebral palsy (CP) children and normal children. MethodsThis study involved fourteen children aged from 4 to 7 years with CP (monoplegia) between 2009 and 2013. Another 14 normal children aged from 5 to 9 years treated in the Department of Ophthalmology in West China Hospital during the same period were regarded as the control group. Both eyes of all the participants were examined by multifocal visual evoked potential (mfVEP). The mfVEP examination results were recorded, and amplitude and latency were analyzed. First, we analyzed the differences of amplitudes and latency time between monoplegia children and children in the control group. Second, gross motor function classification system (GMFCS) was used to classify the fourteen monoplegia children among whom there were five GMFCS Ⅰ patients and nine GMFCS Ⅱ patients. The differences of mfVEP were analyzed between the two GMFCS groups. ResultsThe amplitude and latency of mfVEP in children with CP showed gradual changes similar to those in the normal children. The amplitudes were decreasing and the latencies were delaying from the first eccentricity to the sixth eccentricity. The amplitudes in children with CP were lower than those in the control group in the first to the third eccentricities for both eyes (P＜0.05), and latency of left eye was delayed in the first eccentricity in children with CP (P=0.045). No difference was found between the two GMFCS groups (P>0.05) except the amplitude of the first eccentricity (P=0.043). ConclusionsThe results of mfVEP show significant differences of amplitude and latency between CP and normal children, suggesting the existence of visual pathway impairments in cerebral palsy children. The results of mfVEP can provide an objective basis of visual impairments for cerebral palsy children.
Objective To investigate the characteristic of the multifocal visual evoked potentials(MVEP)and the visual function across the visual field in anisometropic amblyopes and isometropic amblyopes. Methods MVEP from 32 anisometropic amblyopic eyes and 31 control eyes were tested. Results In anisometropic amblyopic eyes,the latencies of MVEP were significantly prolonged．The amplitudes of MVEP were significantly attenuated in the central region of the visual field,and these phenomena gradually reduced with the increase of the eccentricity． Conclusion The visual function of anisometropic amblyopic eyes is reduced more significantly in the central region than in the peripheral region of the visual field. (Chin J Ocul Fundus Dis,20000,16:27-29)
Rapid serial visual presentation-brain computer interface (RSVP-BCI) is the most popular technology in the early discover task based on human brain. This algorithm can obtain the rapid perception of the environment by human brain. Decoding brain state based on single-trial of multichannel electroencephalogram (EEG) recording remains a challenge due to the low signal-to-noise ratio (SNR) and nonstationary. To solve the problem of low classification accuracy of single-trial in RSVP-BCI, this paper presents a new feature extraction algorithm which uses principal component analysis (PCA) and common spatial pattern (CSP) algorithm separately in spatial domain and time domain, creating a spatial-temporal hybrid CSP-PCA (STHCP) algorithm. By maximizing the discrimination distance between target and non-target, the feature dimensionality was reduced effectively. The area under the curve (AUC) of STHCP algorithm is higher than that of the three benchmark algorithms (SWFP, CSP and PCA) by 17.9%, 22.2% and 29.2%, respectively. STHCP algorithm provides a new method for target detection.
Motor imaging therapy is of great significance to the rehabilitation of patients with stroke or motor dysfunction, but there are few studies on lower limb motor imagination. When electrical stimulation is applied to the posterior tibial nerve of the ankle, the steady-state somatosensory evoked potentials (SSSEP) can be induced at the electrical stimulation frequency. In order to better realize the classification of lower extremity motor imagination, improve the classification effect, and enrich the instruction set of lower extremity motor imagination, this paper designs two experimental paradigms: Motor imaging (MI) paradigm and Hybrid paradigm. The Hybrid paradigm contains electrical stimulation assistance. Ten healthy college students were recruited to complete the unilateral movement imagination task of left and right foot in two paradigms. Through time-frequency analysis and classification accuracy analysis, it is found that compared with MI paradigm, Hybrid paradigm could get obvious SSSEP and ERD features. The average classification accuracy of subjects in the Hybrid paradigm was 78.61%, which was obviously higher than the MI paradigm. It proves that electrical stimulation has a positive role in promoting the classification training of lower limb motor imagination.
To evaluate the value of clinical application of examination of fibrillation potential amplitude, 110 patients, 97 males and 13 females, were examined and only the maximum fibrillation potential amplitudes were recorded in 420 muscles. The results showed that there was no significant difference between sexes, ages and sides. However, significant difference was evident between the groups of different frequency (1+ to 4+). The fibrillation potential amplitude was maximum at 3 to 4 months after denervation and still remained at relatively high level for years in certain patients. No significant difference was showed between the time groups in incomplete nerve injuries. Surgery did not affect the course of fibrillation potential amplitude change. It was suggested that the muscle cells sustained their property for years after denervation in some patients, thus it might explain that satisfactory result could be obtained from operative repair in some late cases. The changes of fibrillation potential amplitude might indicate that the changes from muscle denervation was still reversible and might be more accurate than traditional method of examination.
The purpose of this study is to investigate the change of the whole brain event-related potentials(P300) in normal brain aging based on N-back cognitive tasks. The P300 of 15 normal young people and 10 normal old people were evaluated based on N-back cognitive tasks and analyzed. The results showed that the P300 latency of old people was longer in whole brain than young people, and amplitude was increased in the frontal-central region, while significantly increased in the pre-frontal region in the same load cognitive tasks. With the cognitive task load increasing, the amplitude of old people in high-load task was higher in the whole brain than that in low-load task, mainly in in the frontal region, but the difference was not statistically significant. The latency in the high-load task was shorter in the frontal-central region of right brain than the low-load task, and the difference was statistically significant. Thus, P300 showed that the normal brain aging process is mainly reflected in the pre-frontal region, and the high-load cognitive task could better reflect the change of brain function compared with the low-load cognitive task. The finding is of revelatory meaning for diagnosis of early dementia in patients.
Brain-computer interface (BCI) systems based on steady-state visual evoked potential (SSVEP) have become one of the major paradigms in BCI research due to their high signal-to-noise ratio and short training time required by users. Fast and accurate decoding of SSVEP features is a crucial step in SSVEP-BCI research. However, the current researches lack a systematic overview of SSVEP decoding algorithms and analyses of the connections and differences between them, so it is difficult for researchers to choose the optimum algorithm under different situations. To address this problem, this paper focuses on the progress of SSVEP decoding algorithms in recent years and divides them into two categories—trained and non-trained—based on whether training data are needed. This paper also explains the fundamental theories and application scopes of decoding algorithms such as canonical correlation analysis (CCA), task-related component analysis (TRCA) and the extended algorithms, concludes the commonly used strategies for processing decoding algorithms, and discusses the challenges and opportunities in this field in the end.