Publications by authors named "Xinyi Geng"

14 Publications

  • Page 1 of 1

Objective Assessments of Mental Fatigue During a Continuous Long-Term Stress Condition.

Front Hum Neurosci 2021 10;15:733426. Epub 2021 Nov 10.

Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China.

Prolonged periods of cognitive workload will cause mental fatigue, but objective, quantitative, and sensitive measurements that reflect long-term, stress-induced mental fatigue have yet to be elucidated. This study aims to apply a potential marker of Rényi entropy to investigate the mental fatigue changes in a long-term, high-level stress condition and compare three different instruments for assessment of mental fatigue: EEG, the oddball task, and self-scoring. We recruited nine individuals who participated in a 5-day intellectually challenging competition. The participants were assessed for mental fatigue each day of the competition using prefrontal cortex electroencephalogram (EEG). Reaction time in an oddball task and self-rated scoring were used comparatively to evaluate the performance of the EEG. Repeated measures ANOVA was utilized to analyze the differences among score, reaction time, and wavelet Rényi entropy. The results demonstrated that both wavelet Rényi entropy extracted from EEG and self-rated scoring revealed significant increases in mental fatigue during the 5 days of competition ( < 0.001). The reaction time of the oddball task did not show significant changes during the five-day competition ( = 0.066). Moreover, the wavelet Rényi entropy analysis of EEG showed greater sensitivity than the self-rated scoring and reaction time of the oddball task for measuring mental fatigue changes. In conclusion, this study shows that mental fatigue accumulates during long-term, high-level stress situations. The study also indicates that EEG wavelet Rényi entropy is an efficient metric to reflect the change of mental fatigue under a long-term stress condition and that EEG is a better method to assess long-term mental fatigue.
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http://dx.doi.org/10.3389/fnhum.2021.733426DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8631328PMC
November 2021

Real-time removal of stimulation artifacts in closed-loop deep brain stimulation.

J Neural Eng 2021 Nov 24. Epub 2021 Nov 24.

Institute of Science and Technology for Brain-inspired Intelligence, Fudan University, 220 Handan Road, Yangpu District, Shanghai, 200433, CHINA.

Objective: Closed-loop deep brain stimulation (DBS) with neural feedback has shown great potential in improving the therapeutic effect and reducing side effects. However, the amplitude of stimulation artifacts is much larger than the local field potentials, which remains a bottleneck in developing a closed-loop stimulation strategy with varied parameters.

Approach: We proposed an irregular sampling method for the real-time removal of stimulation artifacts. The artifact peaks were detected by applying a threshold to the raw recordings, and the samples within the contaminated period of the stimulation pulses were excluded and replaced with the interpolation of the samples prior to and after the stimulation artifact duration. This method was evaluated with both simulation signals and in vivo closed-loop DBS applications in Parkinsonian animal models.

Main Results: The irregular sampling method was able to remove the stimulation artifacts effectively with the simulation signals. The relative errors between the power spectral density of the recovered and true signals within a wide frequency band (2-150 Hz) were 2.14%, 3.93%, 7.22%, 7.97% and 6.25% for stimulation at 20 Hz, 60 Hz, 130 Hz, 180 Hz, and stimulation with variable low and high frequencies, respectively. This stimulation artifact removal method was verified in real-time closed-loop DBS application in vivo, and the artifacts were effectively removed during stimulation with frequency continuously changing from 130 Hz to 1 Hz and stimulation adaptive to beta oscillations.

Significance: The proposed method provides an approach for real-time removal in closed-loop DBS applications, which is effective in stimulation with low frequency, high frequency, and variable frequency. This method can facilitate the development of more advanced closed-loop DBS strategies.
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http://dx.doi.org/10.1088/1741-2552/ac3cc5DOI Listing
November 2021

Subthalamic dynamic neural states correlate with motor symptoms in Parkinson's Disease.

Clin Neurophysiol 2021 11 25;132(11):2789-2797. Epub 2021 Aug 25.

Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China; Key Laboratory of Computational Neuroscience and Brain-Inspired Intelligence (Fudan University), Ministry of Education, China; MOE Frontiers Center for Brain Science, Ministry of Education, Fudan University, Shanghai, China; Shanghai Engineering Research Center of AI & Robotics, Fudan University, Shanghai, China; Engineering Research Center of AI & Robotics, Ministry of Education, Fudan University, Shanghai, China. Electronic address:

Objective: This study aims to discriminate the dynamic synchronization states from the subthalamic local field potentials and investigate their correlations with the motor symptoms in Parkinson's Disease (PD).

Methods: The resting-state local field potentials of 10 patients with PD were recorded from the subthalamic nucleus. The dynamic neural states of multiple oscillations were discriminated and analyzed. The Spearman correlation was used to investigate the correlations between occurrence rate or duration of dynamic neural states and the severity of motor symptoms.

Results: The proportion of long low-beta and theta synchronized state was significantly correlated with the general motor symptom and tremor, respectively. The duration of combined low/high-beta state was significantly correlated with rigidity, and the duration of combined alpha/high-beta state was significantly correlated with bradykinesia.

Conclusions: This study provides evidence that motor symptoms are associated with the neural states coded with multiple oscillations in PD.

Significance: This study may advance the understanding of the neurophysiological mechanisms of the motor symptoms and provide potential biomarkers for closed-loop deep brain stimulation in PD.
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http://dx.doi.org/10.1016/j.clinph.2021.07.022DOI Listing
November 2021

Deep brain stimulation in the globus pallidus modulates pallidal and subthalamic neural oscillations.

Annu Int Conf IEEE Eng Med Biol Soc 2019 Jul;2019:5204-5207

Deep brain stimulation (DBS) in the basal ganglia has been introduced to treat movement disorders. The effects of pallidal DBS on the neural oscillations in the globus pallidus interna (GPi) and the subthalamic nucleus (STN) of the same subject remains unclear. In this study, the DBS electrodes were bilaterally implanted in the GPi and STN in patients with Tourette's syndrome (TS). The local field potentials were simultaneously recorded from the GPi and STN during pallidal DBS with 130 Hz, 60 microseconds, and 1V/2V/2.5V voltages. The time-frequency characteristics were analyzed across the conditions of resting, stimulation and post-stimulation. The results showed that alpha and beta oscillation existed in the basal ganglia and the beta oscillation was attenuated by pallidal stimulation. The attenuations are significantly different among 1V/2V/2.5V voltages. The results suggest that beta oscillations may have physiological function in resisting tics in TS. Thus, the oscillation- and symptom-guided intelligent DBS needs to be investigated.
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http://dx.doi.org/10.1109/EMBC.2019.8856535DOI Listing
July 2019

Epileptic States Recognition Using Transfer Learning.

Annu Int Conf IEEE Eng Med Biol Soc 2019 Jul;2019:2539-2542

Automatic recognition of electroencephalogram (EEG) signals plays a major role in epilepsy diagnosis and assessment. However, the recognition accuracy of conventional methods is usually not satisfactory because of the inconsistent distribution of training and testing data in practical applications. To overcome this problem, we used cross-domain mean joint approximation embedding (CMJAE) transductive transfer learning method to realize the knowledge transfer from the training data to the testing data by measuring the distribution difference between them. We combined the subspace learning and joint distribution to adapt the marginal and conditional distribution discrepancy. Our method was able to effectively learn a model for the testing data from training data with different distribution at a low computational complexity cost. On a public dataset, an ad-hoc cross-validation scheme of the proposed method exhibited that the average recognition accuracy, sensitivity, specificity of different states was 97.5%, 94.3%, 92.7% respectively, much better than conventional machine learning or deep learning methods, which may serve as a promising strategy for epileptic states recognition algorithms.
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http://dx.doi.org/10.1109/EMBC.2019.8857265DOI Listing
July 2019

Functional dynamics of thalamic local field potentials correlate with modulation of neuropathic pain.

Eur J Neurosci 2020 01 23;51(2):628-640. Epub 2019 Sep 23.

Neural and Intelligence Engineering Center, Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China.

Understanding the functional dynamics of neural oscillations in the sensory thalamus is essential for elucidating the perception and modulation of neuropathic pain. Local field potentials were recorded from the sensory thalamus of twelve neuropathic pain patients. Single and combinational neural states were defined by the activity state of a single or paired oscillations. Relationships between the duration or occurrence rate of neural state and pre-operative pain level or pain relief induced by deep brain stimulation were evaluated. Results showed that the occurrence rate of the single neural state of low-beta oscillation was significantly correlated with pain relief. The duration and occurrence rate of combinational neural states of the paired low-beta with delta, theta, alpha, high-beta or low-gamma oscillations were more significantly correlated with pain relief than the single neural states. Moreover, these significant combinational neural states formed a local oscillatory network with low-beta oscillation as a key node. The results also showed correlations between measures of combinational neural states and subjective pain level as well. The duration of combinational neural states of paired alpha with delta or theta oscillations and the occurrence rate of neural states of the paired delta with low-beta or low-gamma oscillations were significantly correlated with pre-operative pain level. In conclusion, this study revealed that the integration of oscillations and the functional dynamics of neural states were differentially involved in modulation and perception of neuropathic pain. The functional dynamics could be biomarkers for developing neural state-dependent deep brain stimulation for neuropathic pain.
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http://dx.doi.org/10.1111/ejn.14569DOI Listing
January 2020

Characteristics of Globus Pallidus Internus Local Field Potentials in Hyperkinetic Disease.

Front Neurol 2018 5;9:934. Epub 2018 Nov 5.

Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, China.

Dystonia and Huntington's disease (HD) are both hyperkinetic movement disorders but exhibit distinct clinical characteristics. Aberrant output from the globus pallidus internus (GPi) is involved in the pathophysiology of both HD and dystonia, and deep brain stimulation (DBS) of the GPi shows good clinical efficacy in both disorders. The electrode externalized period provides an opportunity to record local field potentials (LFPs) from the GPi to examine if activity patterns differ between hyperkinetic disorders and are associated with specific clinical characteristics. LFPs were recorded from 7 chorea-dominant HD and nine cervical dystonia patients. Differences in oscillatory activities were compared by power spectrum and Lempel-Ziv complexity (LZC). The discrepancy band power ratio was used to control for the influence of absolute power differences between groups. We further identified discrepant frequency bands and frequency band ratios for each subject and examined the correlations with clinical scores. Dystonia patients exhibited greater low frequency power (6-14 Hz) while HD patients demonstrated greater high-beta and low-gamma power (26-43 Hz) ( < 0.0298, corrected). United Huntington Disease Rating Scale chorea sub-score was positively correlated with 26-43 Hz frequency band power and negatively correlated with the 6-14 Hz/26-43 Hz band power ratio. Dystonia and HD are characterized by distinct oscillatory activity patterns, which may relate to distinct clinical characteristics. Specifically, chorea may be related to elevated high-beta and low-gamma band power, while dystonia may be related to elevated low frequency band power. These LFPs may be useful biomarkers for adaptive DBS to treat hyperkinetic diseases.
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http://dx.doi.org/10.3389/fneur.2018.00934DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6230660PMC
November 2018

Oscillatory local field potentials of the nucleus accumbens and the anterior limb of the internal capsule in heroin addicts.

Clin Neurophysiol 2018 06 30;129(6):1242-1253. Epub 2018 Mar 30.

Department of Neurosurgery, Tangdu Hospital, Fourth Military Medical University, Xi'an 710038, China. Electronic address:

Objectives: The nucleus accumbens (NAc) is known to regulate the motivation and underlie addictive behaviors, and the anterior limb of the internal capsule (ALIC) is involved in several psychiatric disorders. Our study aimed to explore the functions of NAc and ALIC electrophysiologically.

Methods: The local field potentials (LFPs) of the NAc and ALIC were recorded from 7 heroin addicts treated with deep brain stimulation. Correlation analysis was made between LFP powers in various frequency bands and the subjects' neuropsychological test scores; coherence was calculated for the LFPs in NAc and ALIC.

Results: Both the NAc and ALIC exhibited prominent theta and alpha frequency band activity in the LFP power spectra. Additionally, a distinct beta band peak was detected in the power spectra of ALIC LFPs, which may represent the activity of striatal bridge cells. There was a significant negative correlation between the power of the theta frequency band of ALIC LFPs and visual analogue scale (VAS) scores indicative of cravings (Spearman's ρ = -0.758, P = 0.002), and a significant positive correlation was found between the power of the alpha frequency band of NAc LFPs and subjects' scores on the Hamilton depression inventory (ρ = 0.727, P = 0.005). LFPs of the NAc and ALIC exhibited higher coherence values in the theta and alpha frequency bands.

Conclusions: The results suggest that theta power in the ALIC/dorsal striatum and alpha power in the NAc may be associated with drug cravings and depressive symptoms, respectively, in heroin addicts. For these subjects, the neural activities in the dorsal and ventral striatum were mainly coordinated within the low-frequency band.

Significance: The study illustrates the neurophysiologic characteristics of heroin addiction and its comorbidities, providing a potential theoretical basis for optimizing deep brain stimulation (DBS) therapy.
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http://dx.doi.org/10.1016/j.clinph.2018.03.008DOI Listing
June 2018

Intra-operative characterisation of subthalamic oscillations in Parkinson's disease.

Clin Neurophysiol 2018 05 27;129(5):1001-1010. Epub 2018 Feb 27.

Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China. Electronic address:

Objective: This study aims to use the activities recorded directly from the deep brain stimulation (DBS) electrode to address the focality and distinct nature of the local field potential (LFP) activities of different frequency.

Methods: Pre-operative and intra-operative magnetic resonance imaging (MRI) were acquired from patients with Parkinson's disease (PD) who underwent DBS in the subthalamic nucleus and intra-operative LFP recording at rest and during cued movements. Images were reconstructed and 3-D visualized using Lead-DBS® toolbox to determine the coordinates of contact. The resting spectral power and movement-related power modulation of LFP oscillations were estimated.

Results: Both subthalamic LFP activity recorded at rest and its modulation by movement had focal maxima in the alpha, beta and gamma bands. The spatial distribution of alpha band activity and its modulation was significantly different to that in the beta band. Moreover, there were significant differences in the scale and timing of movement related modulation across the frequency bands.

Conclusion: Subthalamic LFP activities within specific frequency bands can be distinguished by spatial topography and pattern of movement related modulation.

Significance: Assessment of the frequency, focality and pattern of movement related modulation of subthalamic LFPs reveals a heterogeneity of neural population activity in this region. This could potentially be leveraged to finesse intra-operative targeting and post-operative contact selection.
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http://dx.doi.org/10.1016/j.clinph.2018.01.075DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5884428PMC
May 2018

Comparison of oscillatory activity in subthalamic nucleus in Parkinson's disease and dystonia.

Neurobiol Dis 2017 Feb 7;98:100-107. Epub 2016 Dec 7.

Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, 88 Keling Road, SND, Suzhou 215163, China.

Objectives: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has been successfully used to treat both Parkinson's disease (PD) and dystonia. Local field potentials (LFPs) recorded from the STN of PD patients demonstrate prominent beta frequency band activity. It is unclear whether such activity occurs in the STN in dystonia, and, if not, whether dystonia has another distinctive neural population activity in the STN.

Methods: Twelve patients with PD, and eight patients with dystonia underwent DBS electrode implantation targeting the STN. Seven dystonia patients were off medication and one was on aripiprazole and clonazepam. LFPs were recorded from the DBS electrodes in PD in the on/off medication states and in dystonia. Power spectra and temporal dynamics measured by the with Lempel-Ziv complexity of the LFPs were compared among these states.

Results: Normalised power spectra and Lempel-Ziv complexity of subthalamic LFPs differed between dystonia off and PD on/off, and between PD off and on over the low frequency, beta and high gamma bands. Patients with dystonia and off medication had lower beta power but higher low frequency and high gamma power than PD. Spectral power in the low beta frequency (11-20Hz) range was attenuated in medicated PD.

Conclusion: The results suggest that dystonia and PD are characterized by different patterns of oscillatory activities even within the same nucleus, and exaggerated beta activity may relate to hypo-dopaminergic status.
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http://dx.doi.org/10.1016/j.nbd.2016.12.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5321603PMC
February 2017

[Influence of Medication on the Oscillatory and Dynamic Characteristics of Subthalamic Local Field Potentials in Patients with Parkinson's Disease].

Sheng Wu Yi Xue Gong Cheng Xue Za Zhi 2016 Feb;33(1):49-55

The dysfunction of subthalamic nucleus is the main cause of Parkinson's disease. Local field potentials in human subthalamic nucleus contain rich physiological information. The present study aimed to quantify the oscillatory and dynamic characteristics of local field potentials of subthalamic nucleus, and their modulation by the medication therapy for Parkinson's disease. The subthalamic nucleus local field potentials were recorded from patients with Parkinson's disease at the states of on and off medication. The oscillatory features were characterised with the power spectral analysis. Furthermore, the dynamic features were characterised with time-frequency analysis and the coefficient of variation measure of the time-variant power at each frequency. There was a dominant peak at low beta-band with medication off. The medication significantly suppressed the low beta component and increased the theta component. The amplitude fluctuation of neural oscillations was measured by the coefficient of variation. The coefficient of variation in 4-7 Hz and 60-66 Hz was increased by medication. These effects proved that medication had significant modulation to subthalamic nucleus neural oscillatory synchronization and dynamic features. The subthalamic nucleus neural activities tend towards stable state under medication. The findings would provide quantitative biomarkers for studying the mechanisms of Parkinson's disease and clinical treatments of medication or deep brain stimulation.
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February 2016

[Three-dimensional Structural Visualization of Subthalamic Nucleus for Deep Brain Stimulation].

Sheng Wu Yi Xue Gong Cheng Xue Za Zhi 2016 Jun;33(3):405-12

The effect of deep brain stimulation(DBS)surgery treatment for Parkinson’s disease is determined by the accuracy of the electrodes placement and localization.The subthalamic nuclei(STN)as the implant target is small and has no clear boundary on the images.In addition,the intra-operative magnetic resonance images(MRI)have such a low resolution that the artifacts of the electrodes impact the observation.The three-dimensional(3D)visualization of STN and other nuclei nearby is able to provide the surgeons with direct and accurate localizing information.In this study,pre-and intra-operative MRIs of the Parkinson’s disease patients were used to realize the 3Dvisualization.After making a co-registration between the high-resolution pre-operative MRIs and the low-resolution intraoperative MRIs,we normalized the MRIs into a standard atlas space.We used a special threshold mask to search the lead trajectories in each axial slice.After checking the location of the electrode contacts with the coronal MRIs of the patients,we reconstructed the whole lead trajectories.Then the STN and other nuclei nearby in the standard atlas space were visualized with the grey images of the standard atlas,accomplishing the lead reconstruction and nerve nuclei visualization near STN of all patients.This study provides intuitive and quantitative information to identify the accuracy of the DBS electrode implantation,which could help decide the post-operative programming setting.
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June 2016

Measuring complex behaviors of local oscillatory networks in deep brain local field potentials.

J Neurosci Methods 2016 May 27;264:25-32. Epub 2016 Feb 27.

Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, China. Electronic address:

Background: Multiple oscillations emerging from the same neuronal substrate serve to construct a local oscillatory network. The network usually exhibits complex behaviors of rhythmic, balancing and coupling between the oscillations, and the quantification of these behaviors would provide valuable insight into organization of the local network related to brain states.

New Method: An integrated approach to quantify rhythmic, balancing and coupling neural behaviors based upon power spectral analysis, power ratio analysis and cross-frequency power coupling analysis was presented. Deep brain local field potentials (LFPs) were recorded from the thalamus of patients with neuropathic pain and dystonic tremor. t-Test was applied to assess the difference between the two patient groups.

Results: The rhythmic behavior measured by power spectral analysis showed significant power spectrum difference in the high beta band between the two patient groups. The balancing behavior measured by power ratio analysis showed significant power ratio differences at high beta band to 8-20 Hz, and 30-40 Hz to high beta band between the patient groups. The coupling behavior measured by cross-frequency power coupling analysis showed power coupling differences at (theta band, high beta band) and (45-55 Hz, 70-80 Hz) between the patient groups.

Comparison With Existing Method: The study provides a strategy for studying the brain states in a multi-dimensional behavior space and a framework to screen quantitative characteristics for biomarkers related to diseases or nuclei.

Conclusions: The work provides a comprehensive approach for understanding the complex behaviors of deep brain LFPs and identifying quantitative biomarkers for brain states related to diseases or nuclei.
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http://dx.doi.org/10.1016/j.jneumeth.2016.02.018DOI Listing
May 2016

[Cross Frequency Coupling Characteristic Analysis in Subthalamic Local Field Potentials of Parkinson's Disease].

Sheng Wu Yi Xue Gong Cheng Xue Za Zhi 2015 Aug;32(4):874-80

Pathological neural activity in subthalamic nucleus (STN) is closely related to the symptoms of Parkinson' s disease. Local field potentials (LFPs) recordings from subthalamic nucleus show that power spectral peaks exist at tremor, double tremor and tripble tremor frequencies, respectively. The interaction between these components in the multi-frequency tremor may be related to the generation of tremor. To study the linear and nonlinear relationship between those components, we analyzed STN LFPs from 9 Parkinson's disease patients using time frequency, cross correlation, Granger casuality and bi-spectral analysis. Results of the time-frequency analysis and cross-frequency correlation analysis demonstrated that the power density of those components significantly decreased as the alleviation of tremor and cross-correlation (0.18-0.50) exists during tremor period. Granger causality of the time-variant amplitude showed stronger contribution from tremor to double tremor components, and contributions from both tremor and double tremor components to triple tremor component. Quadratic phase couplings among these three components were detected by the bispectral approaches. The linear and nonlinear relationships existed among the multi-components and certainly confirmed that the dependence cross those frequencies and neurological mechanism of tremor involved complicate neural processes.
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August 2015
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