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At least 271 records · Page 15Linked to original sources
PubMed2005

Brain mapping of visual evoked activity--topographical and functional components.

Electroencephalographic (EEG) and evoked activity can be recorded non-invasively in order to monitor human brain activation online. Electrical fields are generated by large intracranial neural populations and spread to the scalp through volume conduction. All measured signals depend on the location of the recording and reference electrodes. Simultaneous recordings from many scalp positions allow for a topographical assessment of the complete electrical fields of the brain and avoid problems typically seen with time series analysis. The present contribution will illustrate the fundamentals of topographic mapping of human electrophysiological brain activity as well as quantitative analysis methods. Visual evoked potential data obtained in a group of 12 healthy adults are presented. We will focus on the definition and identification of evoked components that represent steps in visual information processing. In addition, the application of statistical data reduction techniques are described, and the results of functional components which are related to experimental variations are discussed.

Brain Mapping↗
PubMed1995

Applications of magnetic source imaging to presurgical brain mapping.

This article highlights the patient benefits of noninvasive presurgical mapping using magnetic source imaging, discusses magnetic source imaging in terms of its practical implementation and current limitations in mapping the human cerebral cortex, and illustrates the use of magnetic source imaging in ongoing clinical studies. An overview of preliminary research studies that have attempted to evaluate the accuracy and cost-effectiveness of magnetic source imaging in presurgical mapping is also provided.

Adult↗
PubMedDate not supplied

Intractable epilepsy and structural lesions of the brain: mapping, resection strategies, and seizure outcome.

Forty-seven patients with structural brain lesions on neuroimaging studies and partial epilepsy intractable to medical therapy were studied. Prolonged noninvasive interictal and ictal EEG recording was performed, followed by more focused mapping using chronically implanted subdural electrode plates. Surgical procedures included lesion biopsy, maximal lesion excision, and/or resection of zones of epileptogenesis depending on accessibility and involvement of speech or other functional areas. The epileptogenic zone involved exclusively the region adjacent to the structural lesion in 11 patients. It extended beyond the lesion in 18 patients. Eighteen other patients had remote noncontiguous zones of epileptogenesis. Postoperative control of epilepsy was accomplished in 17 of 18 patients (94%) with complete lesion excision regardless of extent of seizure focus excision. Postoperative control of epilepsy was accomplished in 5 of 6 patients (83%) with incomplete lesion excision but complete seizure focus excision and in 12 of 23 patients (52%) with incomplete lesion excision and incomplete focus excision. The extent of lesion resection was strongly associated with surgical outcome either in itself (p less than 0.003), or in combination with focus excision. Focus resection was marginally associated with surgical outcome as a dichotomous variable (p = 0.048) and showed a trend toward significance (p = 0.07) only as a three-level outcome variable. We conclude that structural lesions are associated with zones of epileptogenesis in neighboring and remote areas of the brain. Maximum resection of the lesion offers the best chance at controlling intractable epilepsy; however, seizure control is achieved in many patients by carefully planned subtotal resection of lesions or foci.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2003

A unified non-rigid feature registration method for brain mapping.

This paper describes the design, implementation and results of a unified non-rigid feature registration method for the purposes of anatomical MRI brain registration. An important characteristic of the method is its ability to fuse different types of anatomical features into a single point-set representation. We demonstrate the application of the method using two different types of features: the outer cortical surface and major sulcal ribbons. Non-rigid registration of the combined feature point-sets is then performed using a new robust non-rigid point matching algorithm. The point matching algorithm implements an iterative joint clustering and matching (JCM) strategy which effectively reduces the computational complexity without sacrificing accuracy. We have conducted carefully designed synthetic experiments to gauge the effect of using different types of features either separately or together. A validation study examining the accuracy of non-rigid alignment of many brain structures is also presented. Finally, we present anecdotal results on the alignment of two subject MRI brain data.

Algorithms↗
PubMed2004

[Transcranial magnetic stimulation (TMS): physiology, psychology, brain mapping and clinical applications].

Non-invasive Transcranial Magnetic Stimulation (TMS) can painlessly induce conductive current to excite cortex. This changes physiological processing in the brain. Varying the parameters of TMS, differential physiologic effects, psychological impacts can be examined. Modulation of sensory perception, suppression or facilitation of cognitive capacity and behavioral performance depicts differential modulatory operation in the brain. TMS could be applied in the research of neurological disease, psychiatric disorders, and pharmacological investigation. Stereotaxic and frameless TMS can improve the anatomy-guided TMS and use for navigation in brain surgery. Finally, the principles derived from acupuncture mechanisms can be integrated into the frequency modulation effects on the brain, shared by TMS.

Brain Mapping↗
PubMed1996

Statistical approaches to human brain mapping by functional magnetic resonance imaging.

Proper use of functional neuro-imaging through effective experimental design and modern statistical analysis provides new insights in current brain research. This tutorial has two aims: to describe aspects of this technology to applied statisticians and to provide some statistical ideas to neuroscientists unfamiliar with quantitative analytic methods that accommodate randomness. Introductory background material and ample references to current literature on the physics of magnetic resonance imaging, Fourier methods for image reconstruction and measures of image quality are included. Two of the statistical approaches mentioned here are extensions of established methods for longitudinal data analysis to the frequency domain. A recent case study provides real-world instances of approaches, problems and open questions encountered in current functional neuro-imaging research and an introduction to the analysis of spatial time series in this context.

Algorithms↗
PubMed2001

[New insights into brain function by combination of transcranial magnetic stimulation and functional brain mapping].

The present paper aims to summarize potential applications of transcranial magnetic stimulation (TMS) combined with functional brain imaging. Transcranial magnetic stimulation is a well-established noninvasive tool for stimulating circumscribed areas of the human cortex. Functional imaging techniques such as positron emission tomography, functional magnetic resonance imaging, and electroencephalographic mapping enable assessment of TMS-related functional brain activation. A combination of TMS and functional imaging can be useful in three principal ways. (1) Brain imaging before TMS is helpful in defining the accurate coil position over a distinct cortical area which is targeted by TMS. Since TMS can be used to interfere with regional cortical function during a given task, the effects of focal TMS on task performance can help to clarify the task-specific functional contribution of a given cortical area which has previously shown task-related activation in a functional imaging study. (2) Imaging the brain during TMS is a promising approach for assessing cortical excitability and intracerebral functional connectivity. (3) By evaluating lasting effects of TMS, brain imaging after TMS can be employed to study the plasticity of the human cortex. Moreover, this approach will help to advance our understanding of therapeutical effects related to TMS.

Brain↗
PubMed2006

Longitudinal stability of MRI for mapping brain change using tensor-based morphometry.

Measures of brain change can be computed from sequential MRI scans, providing valuable information on disease progression, e.g., for patient monitoring and drug trials. Tensor-based morphometry (TBM) creates maps of these brain changes, visualizing the 3D profile and rates of tissue growth or atrophy, but its sensitivity depends on the contrast and geometric stability of the images. As part of the Alzheimer's Disease Neuroimaging Initiative (ADNI), 17 normal elderly subjects were scanned twice (at a 2-week interval) with several 3D 1.5 T MRI pulse sequences: high and low flip angle SPGR/FLASH (from which Synthetic T1 images were generated), MP-RAGE, IR-SPGR (N = 10) and MEDIC (N = 7) scans. For each subject and scan type, a 3D deformation map aligned baseline and follow-up scans, computed with a nonlinear, inverse-consistent elastic registration algorithm. Voxelwise statistics, in ICBM stereotaxic space, visualized the profile of mean absolute change and its cross-subject variance; these maps were then compared using permutation testing. Image stability depended on: (1) the pulse sequence; (2) the transmit/receive coil type (birdcage versus phased array); (3) spatial distortion corrections (using MEDIC sequence information); (4) B1-field intensity inhomogeneity correction (using N3). SPGR/FLASH images acquired using a birdcage coil had least overall deviation. N3 correction reduced coil type and pulse sequence differences and improved scan reproducibility, except for Synthetic T1 images (which were intrinsically corrected for B1-inhomogeneity). No strong evidence favored B0 correction. Although SPGR/FLASH images showed least deviation here, pulse sequence selection for the ADNI project was based on multiple additional image analyses, to be reported elsewhere.

Aged↗