Peter Lin | Stanford University (original) (raw)

Papers by Peter Lin

Journal of Neurosurgery, 2008

The goal of this study was to examine the sensitivity and specificity in preoperative localizatio... more The goal of this study was to examine the sensitivity and specificity in preoperative localization of hand motor cortex by imaging regional event-related desynchronization (ERD) of brainwaves in the beta frequency band (15-25 Hz) involved in self-paced movement. Using magnetoencephalography (MEG), the authors measured ERD that occurred before self-paced unilateral index finger flexion in 66 patients with brain tumors, epilepsy, and arteriovenous malformations. The authors applied an adaptive spatial filtering algorithm to MEG data and found that peaks of the tomographic distribution of beta-band ERD sources reliably localized hand motor cortex compared with electrical cortical stimulation. They also observed high specificity in estimating contralateral hand motor cortical representations relative to somatosensory cortex. Neither presence nor location of tumor changed the qualitative or quantitative location of motor cortex relative to somatosensory cortex. An imaging protocol using ERD obtained by adaptive spatial filtering of MEG data can be used for extremely reliable preoperative localization of hand motor cortex.

Muscle & Nerve, 2006

We describe a 48-year-old woman with seronegative myasthenia gravis (MG) and high-titer of anti-M... more We describe a 48-year-old woman with seronegative myasthenia gravis (MG) and high-titer of anti-MuSK antibody. She had severe bulbar and respiratory weakness with minimal limb weakness for 2 years. Her disease responded poorly to all the conventional immunosuppressive regimens. Treatment with immunoablative dose of cyclophosphamide led to dramatic and sustained remission of her symptoms. High-dose cyclophosphamide is an effective alternative in patients with unusually refractory disease.

Neurology, 2005

The authors report four patients with a syndrome of painless bilateral isolated phrenic neuropath... more The authors report four patients with a syndrome of painless bilateral isolated phrenic neuropathy. Electrophysiologic testing demonstrated active denervation restricted to the diaphragm. Long-term recovery was poor. The authors conclude that bilateral isolated phrenic neuropathy is a cause of painless diaphragmatic paralysis distinguishable from immune brachial plexus neuropathy and other neuromuscular disorders with similar clinical presentation.

Muscle & nerve, 2006

We describe a 48-year-old woman with seronegative myasthenia gravis (MG) and high-titer of anti-M... more We describe a 48-year-old woman with seronegative myasthenia gravis (MG) and high-titer of anti-MuSK antibody. She had severe bulbar and respiratory weakness with minimal limb weakness for 2 years. Her disease responded poorly to all the conventional immunosuppressive regimens. Treatment with immunoablative dose of cyclophosphamide led to dramatic and sustained remission of her symptoms. High-dose cyclophosphamide is an effective alternative in patients with unusually refractory disease.

ABSTRACT Corticomuscular coupling estimated by EEG-EMG coherence may reveal functional cortical d... more ABSTRACT Corticomuscular coupling estimated by EEG-EMG coherence may reveal functional cortical driving of peripheral muscular activity. EEG-EMG coherence in the beta band (15-30 Hz) has been extensively studied under isometric muscle contraction tasks. We attempted to study the time-course of corticomuscular connectivity under a dynamic target tracking task. A new device was developed for the real-time measurement of dynamic force created by pinching the thumb and index finger. Healthy subjects were asked to track visual targets with the feedback forces. Spectral parameters were explored for reliable estimation of event-related coherence and correlogram for representing corticomuscular connectivity.

ABSTRACT Patients that suffer from loss of motor control would benefit from a brain-computer inte... more ABSTRACT Patients that suffer from loss of motor control would benefit from a brain-computer interface (BCI) that would, optimally, be noninvasive, allow multiple dimensions of control, and be controlled with quick and simple means. Ideally, the control mechanism would be natural to the patient so that little training would be required; and the device would respond to these control signals in a predictable way and on a predictable time scale. It would also be important for such a device to be usable by patients capable and incapable of making physical movements. A BCI was created that used electroencephalography (EEG). Multiple dimensions of control were achieved through the movement or motor imagery of the right hand, left hand, tongue, and right foot. The movements were non-sustained to be convenient for the user. The BCI used the 1.5 seconds of the Bereitschaftspotential prior to movement or motor imagery for classification. This could allow the BCI to execute an action on a time scale anticipated by the user. To test this BCI, eight healthy participants were fitted with 29 EEG electrodes over their sensorimotor cortex and one bipolar electrooculography electrode to detect eye movement. Each participant completed six blocks of 100 trials. A trial included visual presentation of three stimuli: a cross, an arrow, and a diamond. Participants rested during the presentation of the cross. The arrow indicated the action that the participant should perform: right hand squeeze, left hand squeeze, press of the tongue against the roof of the mouth, or right foot toe curl. The diamond indicated that the participant should execute the movement during the first three blocks; and that the participant should imagine executing the movement during the last three blocks. Trials affected by motion artifacts, in particular face muscle activity, were removed. Of the remaining data, about 80% were used to train a Bayesian classification and about 20% were used to test this classification. Predi- ction of the four movements reached accuracies above 150% that of random classification for both real and imagined movements. This suggests a promising future for this BCI.

Corticomuscular coupling estimated by EEG-EMG coherence may reveal functional cortical driving of... more Corticomuscular coupling estimated by EEG-EMG coherence may reveal functional cortical driving of peripheral muscular activity. EEG-EMG coherence in the beta band (15-30 Hz) has been extensively studied under isometric muscle contraction tasks. We attempted to study the time-course of corticomuscular connectivity under a dynamic target tracking task. A new device was developed for the real-time measurement of dynamic force created by pinching thumb and index fingers. Four healthy subjects who participated in this study were asked to track visual targets with the feedback forces. Spectral parameters using FFT and complex wavelet were explored for reliable estimation of event-related coherence and EEG-EMG correlogram for representing corticomuscular connectivity. Clearly distinguishable FFT-based coherence and cross-correlogram during the visual target tracking were observed with appropriate hyper-parameters for spectral estimation. The system design and the exploration of signal processing methods in this study supports further exploration of corticomuscular connectivity associated with human motor control.

This study aims to explore whether human intentions to move or cease to move right and left hands... more This study aims to explore whether human intentions to move or cease to move right and left hands can provide four spatiotemporal patterns in single-trial noninvasive EEG signals to achieve a two-dimensional cursor control. Subjects performed motor tasks by either physical movement or motor imagery. Spatial filtering, temporal filtering, feature selection and classification methods were explored to support accurate computer pattern recognition. The performance was evaluated by both offline classification and online two-dimensional cursor control. Event-related desynchronization (ERD) and post-movement event-related synchronization (ERS) were observed on the contralateral hemisphere to the moving hand for both physical movement and motor imagery. The offline classification of four motor tasks provided 10-fold cross-validation accuracy as high as 88% for physical movement and 73% for motor imagery. Subjects participating in experiments with physical movement were able to complete the online game with the average accuracy of 85.5±4.65%; Subjects participating in motor imagery study also completed the game successfully. The proposed brain-computer interface (BCI) provided a new practical multi-dimensional method by noninvasive EEG signal associated with human natural behavior, which does not need long-term training.

To test whether human intentions to sustain or cease movements in right and left hands can be dec... more To test whether human intentions to sustain or cease movements in right and left hands can be decoded reliably from spatially filtered single-trial magnetoencephalographic (MEG) signals for motor execution and motor imagery. Seven healthy volunteers, naïve to BCI technology, participated in this study. Signals were recorded from 275-channel MEG, and synthetic aperture magnetometry (SAM) was employed as the spatial filter. The four-class classification was performed offline. Genetic algorithm based Mahalanobis linear distance (GA-MLD) and direct-decision tree classifier (DTC) techniques were adopted for the classification through 10-fold cross-validation. Through SAM imaging, strong and distinct event-related desynchronization (ERD) associated with sustaining, and event-related synchronization (ERS) patterns associated with ceasing of right and left hand movements were observed in the beta band (15-30Hz) on the contralateral hemispheres for motor execution and motor imagery sessions. Virtual channels were selected from these areas of high activity for the corresponding events as per the paradigm of the study. Through a statistical comparison between SAM-filtered virtual channels from single-trial MEG signals and basic MEG sensors, it was found that SAM-filtered virtual channels significantly increased the classification accuracy for motor execution (GA-MLD: 96.51+/-2.43%) as well as motor imagery sessions (GA-MLD: 89.69+/-3.34%). Multiple movement intentions can be reliably detected from SAM-based spatially filtered single-trial MEG signals. MEG signals associated with natural motor behavior may be utilized for a reliable high-performance brain-computer interface (BCI) and may reduce long-term training compared with conventional BCI methods using rhythm control.

HE preoperative localization of functionally viable brain tissue helps to guide neurosurgical pla... more HE preoperative localization of functionally viable brain tissue helps to guide neurosurgical planning in optimizing the region of resection while allowing for improved postsurgical neurological function. Various neuroimaging techniques, including MS and fMR imaging, are now available to preoperatively map functional brain organization. Coregistering structural MR imaging data to functional data acquired via MS or fMR imaging allows for the intraoperative creation of a neuronavigation system. Magnetic source imaging has been shown to be increasingly important in preoperative planning and complements intraoperative mapping by delineating retained areas of function noninvasively and in advance, and thus reducing the time needed for intraoperative procedures. Peaks in evoked neuromagnetic field data are used to localize dipoles with the aid of source modeling algorithms. Utilizing MS imaging, relevant somatosensory, speech, and motor cortices can be mapped preoperatively to aid surgical navigation and avoid resecting the eloquent cortex. Alternatively, fMR imaging can be used in the preoperative planning, but its temporal resolution is inferior to that of MS imaging because its measured responses are not as directly correlat-ed with evoked electrical activity. Both fMR and MS imaging have been validated as adjuncts to intraoperative mapping. With the increasing use of MS imaging at clinical centers worldwide, the accuracy of functional localization has become paramount.

PLoS ONE, 2011

We investigated the large-scale functional cortical connectivity network in focal hand dystonia (... more We investigated the large-scale functional cortical connectivity network in focal hand dystonia (FHD) patients using graph theoretic measures to assess efficiency. High-resolution EEGs were recorded in 15 FHD patients and 15 healthy volunteers at rest and during a simple sequential finger tapping task. Mutual information (MI) values of wavelet coefficients were estimated to create an association matrix between EEG electrodes, and to produce a series of adjacency matrices or graphs, G, by thresholding with network cost. Efficiency measures of small-world networks were assessed. As a result, we found that FHD patients have economical small-world properties in their brain functional networks in the alpha and beta bands. During a motor task, in the beta band network, FHD patients have decreased efficiency of small-world networks, whereas healthy volunteers increase efficiency. Reduced efficient beta band network in FHD patients during the task was consistently observed in global efficiency, cost-efficiency, and maximum cost-efficiency. This suggests that the beta band functional cortical network of FHD patients is reorganized even during a task that does not induce dystonic symptoms, representing a loss of long-range communication and abnormal functional integration in large-scale brain functional cortical networks. Moreover, negative correlations between efficiency measures and duration of disease were found, indicating that the longer duration of disease, the less efficient the beta band network in FHD patients. In regional efficiency analysis, FHD patients at rest have high regional efficiency at supplementary motor cortex (SMA) compared with healthy volunteers; however, it is diminished during the motor task, possibly reflecting abnormal inhibition in FHD patients. The present study provides the first evidence with graph theory for abnormal reconfiguration of brain functional networks in FHD during motor task.

Neurology, 2009

Background: Traditionally, benign essential blepharospasm (BEB) is considered a disorder caused b... more Background: Traditionally, benign essential blepharospasm (BEB) is considered a disorder caused by basal ganglia dysfunction. Electrophysiologic and brain imaging studies suggest pathologic changes in excitability in the primary motor cortex (MC), anterior cingulate (AC), and secondary motor areas, such as premotor (PMC) and supplementary motor cortices (SMA).

Neurology, 2010

Background: Benign essential blepharospasm (BEB) is a common form of focal dystonia. Besides path... more Background: Benign essential blepharospasm (BEB) is a common form of focal dystonia. Besides pathology in the basal ganglia, accumulating evidence suggests pathologic changes in the anterior cingulate cortex (ACC).

Journal of Neurosurgery, 2008

The goal of this study was to examine the sensitivity and specificity in preoperative localizatio... more The goal of this study was to examine the sensitivity and specificity in preoperative localization of hand motor cortex by imaging regional event-related desynchronization (ERD) of brainwaves in the beta frequency band (15-25 Hz) involved in self-paced movement. Using magnetoencephalography (MEG), the authors measured ERD that occurred before self-paced unilateral index finger flexion in 66 patients with brain tumors, epilepsy, and arteriovenous malformations. The authors applied an adaptive spatial filtering algorithm to MEG data and found that peaks of the tomographic distribution of beta-band ERD sources reliably localized hand motor cortex compared with electrical cortical stimulation. They also observed high specificity in estimating contralateral hand motor cortical representations relative to somatosensory cortex. Neither presence nor location of tumor changed the qualitative or quantitative location of motor cortex relative to somatosensory cortex. An imaging protocol using ERD obtained by adaptive spatial filtering of MEG data can be used for extremely reliable preoperative localization of hand motor cortex.

Muscle & Nerve, 2006

We describe a 48-year-old woman with seronegative myasthenia gravis (MG) and high-titer of anti-M... more We describe a 48-year-old woman with seronegative myasthenia gravis (MG) and high-titer of anti-MuSK antibody. She had severe bulbar and respiratory weakness with minimal limb weakness for 2 years. Her disease responded poorly to all the conventional immunosuppressive regimens. Treatment with immunoablative dose of cyclophosphamide led to dramatic and sustained remission of her symptoms. High-dose cyclophosphamide is an effective alternative in patients with unusually refractory disease.

Neurology, 2005

The authors report four patients with a syndrome of painless bilateral isolated phrenic neuropath... more The authors report four patients with a syndrome of painless bilateral isolated phrenic neuropathy. Electrophysiologic testing demonstrated active denervation restricted to the diaphragm. Long-term recovery was poor. The authors conclude that bilateral isolated phrenic neuropathy is a cause of painless diaphragmatic paralysis distinguishable from immune brachial plexus neuropathy and other neuromuscular disorders with similar clinical presentation.

Muscle & nerve, 2006

We describe a 48-year-old woman with seronegative myasthenia gravis (MG) and high-titer of anti-M... more We describe a 48-year-old woman with seronegative myasthenia gravis (MG) and high-titer of anti-MuSK antibody. She had severe bulbar and respiratory weakness with minimal limb weakness for 2 years. Her disease responded poorly to all the conventional immunosuppressive regimens. Treatment with immunoablative dose of cyclophosphamide led to dramatic and sustained remission of her symptoms. High-dose cyclophosphamide is an effective alternative in patients with unusually refractory disease.

ABSTRACT Corticomuscular coupling estimated by EEG-EMG coherence may reveal functional cortical d... more ABSTRACT Corticomuscular coupling estimated by EEG-EMG coherence may reveal functional cortical driving of peripheral muscular activity. EEG-EMG coherence in the beta band (15-30 Hz) has been extensively studied under isometric muscle contraction tasks. We attempted to study the time-course of corticomuscular connectivity under a dynamic target tracking task. A new device was developed for the real-time measurement of dynamic force created by pinching the thumb and index finger. Healthy subjects were asked to track visual targets with the feedback forces. Spectral parameters were explored for reliable estimation of event-related coherence and correlogram for representing corticomuscular connectivity.

ABSTRACT Patients that suffer from loss of motor control would benefit from a brain-computer inte... more ABSTRACT Patients that suffer from loss of motor control would benefit from a brain-computer interface (BCI) that would, optimally, be noninvasive, allow multiple dimensions of control, and be controlled with quick and simple means. Ideally, the control mechanism would be natural to the patient so that little training would be required; and the device would respond to these control signals in a predictable way and on a predictable time scale. It would also be important for such a device to be usable by patients capable and incapable of making physical movements. A BCI was created that used electroencephalography (EEG). Multiple dimensions of control were achieved through the movement or motor imagery of the right hand, left hand, tongue, and right foot. The movements were non-sustained to be convenient for the user. The BCI used the 1.5 seconds of the Bereitschaftspotential prior to movement or motor imagery for classification. This could allow the BCI to execute an action on a time scale anticipated by the user. To test this BCI, eight healthy participants were fitted with 29 EEG electrodes over their sensorimotor cortex and one bipolar electrooculography electrode to detect eye movement. Each participant completed six blocks of 100 trials. A trial included visual presentation of three stimuli: a cross, an arrow, and a diamond. Participants rested during the presentation of the cross. The arrow indicated the action that the participant should perform: right hand squeeze, left hand squeeze, press of the tongue against the roof of the mouth, or right foot toe curl. The diamond indicated that the participant should execute the movement during the first three blocks; and that the participant should imagine executing the movement during the last three blocks. Trials affected by motion artifacts, in particular face muscle activity, were removed. Of the remaining data, about 80% were used to train a Bayesian classification and about 20% were used to test this classification. Predi- ction of the four movements reached accuracies above 150% that of random classification for both real and imagined movements. This suggests a promising future for this BCI.

Corticomuscular coupling estimated by EEG-EMG coherence may reveal functional cortical driving of... more Corticomuscular coupling estimated by EEG-EMG coherence may reveal functional cortical driving of peripheral muscular activity. EEG-EMG coherence in the beta band (15-30 Hz) has been extensively studied under isometric muscle contraction tasks. We attempted to study the time-course of corticomuscular connectivity under a dynamic target tracking task. A new device was developed for the real-time measurement of dynamic force created by pinching thumb and index fingers. Four healthy subjects who participated in this study were asked to track visual targets with the feedback forces. Spectral parameters using FFT and complex wavelet were explored for reliable estimation of event-related coherence and EEG-EMG correlogram for representing corticomuscular connectivity. Clearly distinguishable FFT-based coherence and cross-correlogram during the visual target tracking were observed with appropriate hyper-parameters for spectral estimation. The system design and the exploration of signal processing methods in this study supports further exploration of corticomuscular connectivity associated with human motor control.

This study aims to explore whether human intentions to move or cease to move right and left hands... more This study aims to explore whether human intentions to move or cease to move right and left hands can provide four spatiotemporal patterns in single-trial noninvasive EEG signals to achieve a two-dimensional cursor control. Subjects performed motor tasks by either physical movement or motor imagery. Spatial filtering, temporal filtering, feature selection and classification methods were explored to support accurate computer pattern recognition. The performance was evaluated by both offline classification and online two-dimensional cursor control. Event-related desynchronization (ERD) and post-movement event-related synchronization (ERS) were observed on the contralateral hemisphere to the moving hand for both physical movement and motor imagery. The offline classification of four motor tasks provided 10-fold cross-validation accuracy as high as 88% for physical movement and 73% for motor imagery. Subjects participating in experiments with physical movement were able to complete the online game with the average accuracy of 85.5±4.65%; Subjects participating in motor imagery study also completed the game successfully. The proposed brain-computer interface (BCI) provided a new practical multi-dimensional method by noninvasive EEG signal associated with human natural behavior, which does not need long-term training.

To test whether human intentions to sustain or cease movements in right and left hands can be dec... more To test whether human intentions to sustain or cease movements in right and left hands can be decoded reliably from spatially filtered single-trial magnetoencephalographic (MEG) signals for motor execution and motor imagery. Seven healthy volunteers, naïve to BCI technology, participated in this study. Signals were recorded from 275-channel MEG, and synthetic aperture magnetometry (SAM) was employed as the spatial filter. The four-class classification was performed offline. Genetic algorithm based Mahalanobis linear distance (GA-MLD) and direct-decision tree classifier (DTC) techniques were adopted for the classification through 10-fold cross-validation. Through SAM imaging, strong and distinct event-related desynchronization (ERD) associated with sustaining, and event-related synchronization (ERS) patterns associated with ceasing of right and left hand movements were observed in the beta band (15-30Hz) on the contralateral hemispheres for motor execution and motor imagery sessions. Virtual channels were selected from these areas of high activity for the corresponding events as per the paradigm of the study. Through a statistical comparison between SAM-filtered virtual channels from single-trial MEG signals and basic MEG sensors, it was found that SAM-filtered virtual channels significantly increased the classification accuracy for motor execution (GA-MLD: 96.51+/-2.43%) as well as motor imagery sessions (GA-MLD: 89.69+/-3.34%). Multiple movement intentions can be reliably detected from SAM-based spatially filtered single-trial MEG signals. MEG signals associated with natural motor behavior may be utilized for a reliable high-performance brain-computer interface (BCI) and may reduce long-term training compared with conventional BCI methods using rhythm control.

HE preoperative localization of functionally viable brain tissue helps to guide neurosurgical pla... more HE preoperative localization of functionally viable brain tissue helps to guide neurosurgical planning in optimizing the region of resection while allowing for improved postsurgical neurological function. Various neuroimaging techniques, including MS and fMR imaging, are now available to preoperatively map functional brain organization. Coregistering structural MR imaging data to functional data acquired via MS or fMR imaging allows for the intraoperative creation of a neuronavigation system. Magnetic source imaging has been shown to be increasingly important in preoperative planning and complements intraoperative mapping by delineating retained areas of function noninvasively and in advance, and thus reducing the time needed for intraoperative procedures. Peaks in evoked neuromagnetic field data are used to localize dipoles with the aid of source modeling algorithms. Utilizing MS imaging, relevant somatosensory, speech, and motor cortices can be mapped preoperatively to aid surgical navigation and avoid resecting the eloquent cortex. Alternatively, fMR imaging can be used in the preoperative planning, but its temporal resolution is inferior to that of MS imaging because its measured responses are not as directly correlat-ed with evoked electrical activity. Both fMR and MS imaging have been validated as adjuncts to intraoperative mapping. With the increasing use of MS imaging at clinical centers worldwide, the accuracy of functional localization has become paramount.

PLoS ONE, 2011

We investigated the large-scale functional cortical connectivity network in focal hand dystonia (... more We investigated the large-scale functional cortical connectivity network in focal hand dystonia (FHD) patients using graph theoretic measures to assess efficiency. High-resolution EEGs were recorded in 15 FHD patients and 15 healthy volunteers at rest and during a simple sequential finger tapping task. Mutual information (MI) values of wavelet coefficients were estimated to create an association matrix between EEG electrodes, and to produce a series of adjacency matrices or graphs, G, by thresholding with network cost. Efficiency measures of small-world networks were assessed. As a result, we found that FHD patients have economical small-world properties in their brain functional networks in the alpha and beta bands. During a motor task, in the beta band network, FHD patients have decreased efficiency of small-world networks, whereas healthy volunteers increase efficiency. Reduced efficient beta band network in FHD patients during the task was consistently observed in global efficiency, cost-efficiency, and maximum cost-efficiency. This suggests that the beta band functional cortical network of FHD patients is reorganized even during a task that does not induce dystonic symptoms, representing a loss of long-range communication and abnormal functional integration in large-scale brain functional cortical networks. Moreover, negative correlations between efficiency measures and duration of disease were found, indicating that the longer duration of disease, the less efficient the beta band network in FHD patients. In regional efficiency analysis, FHD patients at rest have high regional efficiency at supplementary motor cortex (SMA) compared with healthy volunteers; however, it is diminished during the motor task, possibly reflecting abnormal inhibition in FHD patients. The present study provides the first evidence with graph theory for abnormal reconfiguration of brain functional networks in FHD during motor task.

Neurology, 2009

Background: Traditionally, benign essential blepharospasm (BEB) is considered a disorder caused b... more Background: Traditionally, benign essential blepharospasm (BEB) is considered a disorder caused by basal ganglia dysfunction. Electrophysiologic and brain imaging studies suggest pathologic changes in excitability in the primary motor cortex (MC), anterior cingulate (AC), and secondary motor areas, such as premotor (PMC) and supplementary motor cortices (SMA).

Neurology, 2010

Background: Benign essential blepharospasm (BEB) is a common form of focal dystonia. Besides path... more Background: Benign essential blepharospasm (BEB) is a common form of focal dystonia. Besides pathology in the basal ganglia, accumulating evidence suggests pathologic changes in the anterior cingulate cortex (ACC).