2007 4th IEEE International Symposium on Biomedical Imaging: From Nano to Macro - Proceedings, 2007
Visual attention models postulate that relevant information is selectively extracted by different... more Visual attention models postulate that relevant information is selectively extracted by differentially modulating neural activity in the visual cortex to control the response to target and distractor stimuli. To investigate attention bias mecha-nisms in the brain, we use general linear ...
Sulcal and gyral landmarks on the human cerebral cortex are required for various studies of the h... more Sulcal and gyral landmarks on the human cerebral cortex are required for various studies of the human brain. Whether used directly to examine sulcal geometry, or indirectly to drive cortical surface registration methods, the accuracy of these landmarks is essential. While several methods have been developed to automatically identify sulci and gyri, their accuracy may be insufficient for certain neuroanatomical studies. We describe a semi-automated procedure that delineates a sulcus or gyrus given a limited number of user-selected points. The method uses a graph theory approach to identify the lowest-cost path between the points, where the cost is a combination of local curvature features and the distance between vertices on the surface representation. We implemented the algorithm in an interface that guides the user through a cortical surface delineation protocol, and we incorporated this tool into our BrainSuite software. We performed a study to compare the results produced using our method with results produced using Display, a popular tool that has been used extensively for manual delineation of sulcal landmarks. Six raters were trained on the delineation protocol. They performed delineations on 12 brains using both software packages. We performed a statistical analysis of 3 aspects of the delineation task: time required to delineate the surface, registration accuracy achieved compared to an expert-delineated gold-standard, and variation among raters. Our new method was shown to be faster to use, to provide reduced inter-rater variability, and to provide results that were at least as accurate as those produced using Display.
Proceedings of the National Academy of Sciences of the United States of America, 2007
The spiking activity of single neurons in the primate motor cortex is correlated with various lim... more The spiking activity of single neurons in the primate motor cortex is correlated with various limb movement parameters, including velocity. Recent findings obtained using local field potentials suggest that hand speed may also be encoded in the summed activity of neuronal populations. At this macroscopic level, the motor cortex has also been shown to display synchronized rhythmic activity modulated by motor behavior. Yet whether and how neural oscillations might be related to limb speed control is still poorly understood. Here, we applied magnetoencephalography (MEG) source imaging to the ongoing brain activity in subjects performing a continuous visuomotor (VM) task. We used coherence and phase synchronization to investigate the coupling between the estimated activity throughout the brain and the simultaneously recorded instantaneous hand speed. We found significant phase locking between slow (2- to 5-Hz) oscillatory activity in the contralateral primary motor cortex and time-varyi...
Detection of small lesions in fluorodeoxyglucose (FDG) positron emission tomography (PET) is limi... more Detection of small lesions in fluorodeoxyglucose (FDG) positron emission tomography (PET) is limited by image resolution and low signal to noise ratio. We have previously described a matched subspace detection method that uses the time activity curve to distinguish tumors from background in dynamic FDG PET. Applying this algorithm on a voxel by voxel basis throughout the dynamic image produces a test statistic image or "map" which on thresholding indicates the potential locations of secondary or metastatic tumors. In this paper, we describe a thresholding method that controls familywise error rate (FWER) for the matched subspace detection statistical map. The method involves three steps. First, the PET image is segmented into several homogeneous regions. Then, the statistical map is normalized to a zero mean unit variance Gaussian random field. Finally, the images are thresholded at a fixed FWER by estimating their spatial smoothness and applying a random field theory maximum statistic approach. We evaluate this thresholding method using digital phantoms generated from clinical dynamic images. We also present an application of the proposed approach to clinical PET data from a breast cancer patient with metastatic disease.
Magnetoencephalography (MEG) provides unique insights into the spatio-temporal dynamics of neural... more Magnetoencephalography (MEG) provides unique insights into the spatio-temporal dynamics of neural activation in the human brain. Unfortunately, the accuracy with which neural sources can be localized is limited by the highly illposed nature of the inverse problem. A large number of inverse methods have been proposed that deal with this illposedness using a range of different modeling and regularization procedures. Here we describe an objective task-based framework for comparing different inverse methods. Using the free-response receiver operating characteristic (FROC) we compare the performance of matched filters, cortically constrained dipole scanning, and minimum norm imaging methods for the task of detecting focal cortical activation. Our results indicate that the scanning methods outperform matched filters and minimum norm imaging for the case of one and two 2 cm2 patches of cortical activity when the dynamics of the two patches are both strongly and weakly correlated and irrespective of the spacing of the two activated regions.
... PR. Register; Login. Science: Cell Science: Biochemical Genetics; Bioinformatics; Cell Networ... more ... PR. Register; Login. Science: Cell Science: Biochemical Genetics; Bioinformatics; Cell Networks; Cellular and ... and Reaction Engineering; Micro and Nanomaterials. Mathematics: InformationTheory and Signal ... Pharmacology of Anti-Cancer Drugs; Pharmacology of Ion Channels and ...
BrainStorm is a collaborative project to build a software suite for EEG and MEG data visualizat... more BrainStorm is a collaborative project to build a software suite for EEG and MEG data visualization, mod-eling, and source imaging, with integration of MRI and fMRI information. BrainStorm is a Matlab-based toolbox distributed under the GNU public licensing and runs on any ...
2007 4th IEEE International Symposium on Biomedical Imaging: From Nano to Macro - Proceedings, 2007
Visual attention models postulate that relevant information is selectively extracted by different... more Visual attention models postulate that relevant information is selectively extracted by differentially modulating neural activity in the visual cortex to control the response to target and distractor stimuli. To investigate attention bias mecha-nisms in the brain, we use general linear ...
Sulcal and gyral landmarks on the human cerebral cortex are required for various studies of the h... more Sulcal and gyral landmarks on the human cerebral cortex are required for various studies of the human brain. Whether used directly to examine sulcal geometry, or indirectly to drive cortical surface registration methods, the accuracy of these landmarks is essential. While several methods have been developed to automatically identify sulci and gyri, their accuracy may be insufficient for certain neuroanatomical studies. We describe a semi-automated procedure that delineates a sulcus or gyrus given a limited number of user-selected points. The method uses a graph theory approach to identify the lowest-cost path between the points, where the cost is a combination of local curvature features and the distance between vertices on the surface representation. We implemented the algorithm in an interface that guides the user through a cortical surface delineation protocol, and we incorporated this tool into our BrainSuite software. We performed a study to compare the results produced using our method with results produced using Display, a popular tool that has been used extensively for manual delineation of sulcal landmarks. Six raters were trained on the delineation protocol. They performed delineations on 12 brains using both software packages. We performed a statistical analysis of 3 aspects of the delineation task: time required to delineate the surface, registration accuracy achieved compared to an expert-delineated gold-standard, and variation among raters. Our new method was shown to be faster to use, to provide reduced inter-rater variability, and to provide results that were at least as accurate as those produced using Display.
Proceedings of the National Academy of Sciences of the United States of America, 2007
The spiking activity of single neurons in the primate motor cortex is correlated with various lim... more The spiking activity of single neurons in the primate motor cortex is correlated with various limb movement parameters, including velocity. Recent findings obtained using local field potentials suggest that hand speed may also be encoded in the summed activity of neuronal populations. At this macroscopic level, the motor cortex has also been shown to display synchronized rhythmic activity modulated by motor behavior. Yet whether and how neural oscillations might be related to limb speed control is still poorly understood. Here, we applied magnetoencephalography (MEG) source imaging to the ongoing brain activity in subjects performing a continuous visuomotor (VM) task. We used coherence and phase synchronization to investigate the coupling between the estimated activity throughout the brain and the simultaneously recorded instantaneous hand speed. We found significant phase locking between slow (2- to 5-Hz) oscillatory activity in the contralateral primary motor cortex and time-varyi...
Detection of small lesions in fluorodeoxyglucose (FDG) positron emission tomography (PET) is limi... more Detection of small lesions in fluorodeoxyglucose (FDG) positron emission tomography (PET) is limited by image resolution and low signal to noise ratio. We have previously described a matched subspace detection method that uses the time activity curve to distinguish tumors from background in dynamic FDG PET. Applying this algorithm on a voxel by voxel basis throughout the dynamic image produces a test statistic image or "map" which on thresholding indicates the potential locations of secondary or metastatic tumors. In this paper, we describe a thresholding method that controls familywise error rate (FWER) for the matched subspace detection statistical map. The method involves three steps. First, the PET image is segmented into several homogeneous regions. Then, the statistical map is normalized to a zero mean unit variance Gaussian random field. Finally, the images are thresholded at a fixed FWER by estimating their spatial smoothness and applying a random field theory maximum statistic approach. We evaluate this thresholding method using digital phantoms generated from clinical dynamic images. We also present an application of the proposed approach to clinical PET data from a breast cancer patient with metastatic disease.
Magnetoencephalography (MEG) provides unique insights into the spatio-temporal dynamics of neural... more Magnetoencephalography (MEG) provides unique insights into the spatio-temporal dynamics of neural activation in the human brain. Unfortunately, the accuracy with which neural sources can be localized is limited by the highly illposed nature of the inverse problem. A large number of inverse methods have been proposed that deal with this illposedness using a range of different modeling and regularization procedures. Here we describe an objective task-based framework for comparing different inverse methods. Using the free-response receiver operating characteristic (FROC) we compare the performance of matched filters, cortically constrained dipole scanning, and minimum norm imaging methods for the task of detecting focal cortical activation. Our results indicate that the scanning methods outperform matched filters and minimum norm imaging for the case of one and two 2 cm2 patches of cortical activity when the dynamics of the two patches are both strongly and weakly correlated and irrespective of the spacing of the two activated regions.
... PR. Register; Login. Science: Cell Science: Biochemical Genetics; Bioinformatics; Cell Networ... more ... PR. Register; Login. Science: Cell Science: Biochemical Genetics; Bioinformatics; Cell Networks; Cellular and ... and Reaction Engineering; Micro and Nanomaterials. Mathematics: InformationTheory and Signal ... Pharmacology of Anti-Cancer Drugs; Pharmacology of Ion Channels and ...
BrainStorm is a collaborative project to build a software suite for EEG and MEG data visualizat... more BrainStorm is a collaborative project to build a software suite for EEG and MEG data visualization, mod-eling, and source imaging, with integration of MRI and fMRI information. BrainStorm is a Matlab-based toolbox distributed under the GNU public licensing and runs on any ...
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Papers by D. Pantazis