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PubMed1995

Introduction of magnetoencephalography to stereotactic techniques.

Magnetoencephalography (MEG), a noninvasive functional brain mapping technique, was used for preoperative localization of the sensorimotor cortex in patients harboring lesions involving these eloquent regions. Prior to surgery, MEG source locations were transferred onto high-resolution MRI pictures which were then used for preoperative evaluation, risk analysis, and planning. We have developed a process to transform the MEG-derived sensorimotor localization coordinates into the COMPASS stereotactic coordinate system. Thus the MEG-derived functional information is incorporated into the stereotactic database, enabling the simultaneous visualization of functional and anatomical data. This information can be used for the selection of cases and in planning safe approaches for computer-assisted volumetric resections. The integration of MEG and stereotactic neurosurgery also allows a more precise comparison between MEG and intraoperative direct electrocorticographic mapping (ECoG). Seven patients were studied with good correlation between MEG and intraoperative mapping. In 4, the correlation was only based on gross visual comparison between intraoperative identification of the gyrus pattern and MEG photographs. The availability of the MEG coordinates in the stereotactic system, however, allows a more precise correlation between MEG and ECoG. In all 3 patients studied in this manner, the MEG coordinates (pinpointed to a precise cortical representation of a few millimeters) overlapped with ECoG results. In summary, we compared functional MEG data to intraoperative ECoG and conclude that the introduction of MEG into stereotactic neurosurgery can provide precise functional and anatomic information for image-guided surgical planning and resection.

Brain Mapping↗

PubMed2003

Cingulate fasciculus integrity disruption in schizophrenia: a magnetic resonance diffusion tensor imaging study.

Evidence suggests that a disruption in limbic system network integrity and, in particular, the cingulate gyrus (CG), may play a role in the pathophysiology of schizophrenia; however, the cingulum bundle (CB), the white matter tract furnishing both input and output to CG, and the most prominent white matter fiber tract in the limbic system, has not been evaluated in schizophrenia using the new technology of diffusion tensor imaging (DTI). We used line scan DTI to evaluate diffusion in the CB in 16 male schizophrenia patients and 18 male control subjects, group-matched for age, parental socioeconomic status, and handedness. We acquired 4-mm-thick coronal slices through the entire brain. Maps of fractional anisotropy (FA) were generated to quantify diffusion within the left and right CB on eight slices that included the central portion of the CB. Results showed group differences, bilaterally, in area and mean FA for CB, where patients showed smaller area and less anisotropy than controls. For patients, decreased left CB correlated significantly with attention and working memory measures as assessed by the Wisconsin Card Sorting Test. These data provide strong evidence for CB disruptions in schizophrenia, which may be related to disease-related attention and working memory abnormalities.

Adult↗

PubMed2004

Online retrieval, processing, and visualization of primate connectivity data from the CoCoMac database.

Connectivity is the key to understanding distributed and cooperative brain functions. Detailed and comprehensive data on large-scale connectivity between primate brain areas have been collated systematically from published reports of experimental tracing studies. Although the majority of the data have been made easily available for online retrieval, the multiplicity of brain maps and the precise requirements of anatomical naming limit the intuitive access to the data. The quality of data retrieval can be improved by observing a small set of conventions in data representation. Standardized interfaces open up further opportunities for automated search and retrieval, for flexible visualization of data, and for interoperability with other databases. This article provides a discussion and examples in text and image of the capabilities of the online interface to the CoCoMac database of primate connectivity. These serve to point out sources of potential confusion and failure, and to demonstrate the automated interfacing with other neuroinformatics resources that facilitate selection and processing of connectivity data, for example, for computational modelling and interpretation of functional imaging studies.

Animals↗

PubMed2003

Hippocampal deformities in the unaffected siblings of schizophrenia subjects.

BACKGROUND: Neuroanatomical abnormalities have been reported in schizophrenia subjects and their relatives and may be related to genetic vulnerability. The objective of this study was to further elucidate hippocampal deformities as a marker of genetic vulnerability for schizophrenia. METHODS: Magnetic resonance scans were collected in 13 pairs of schizophrenics and their unaffected siblings from families with multiple affected members, in 12 schizophrenics from families without another affected member, and in 10 healthy controls. Hippocampal volume and shape were compared using large-deformation high-dimensional brain mapping. RESULTS: Decreases in hippocampal volume, covaried for total cerebral volume, were observed in the schizophrenia subjects from families with multiple affected members, as well as in their unaffected siblings. Shape analysis demonstrated that both groups of schizophrenia subjects, as well as the unaffected siblings, could be distinguished from the controls; however, no significant difference in hippocampal shape was found between the schizophrenia subjects and their unaffected siblings. Visualization of the pattern of hippocampal shape deformity in both groups of schizophrenia subjects and in the unaffected siblings showed inward deformities of the head of the hippocampus. CONCLUSIONS: Deformations of hippocampal anatomy may be related to the genetic vulnerability of acquiring schizophrenia.

Adult↗

PubMed1998

Estimation of the probabilities of 3D clusters in functional brain images.

The interpretation of functional brain images is often hampered by the presence of noise. This problem is most commonly solved by using a statistical method and only considering signals that are unlikely to occur by chance. The method used should be specific and sensitive, specific because only true signals are of interest and sensitive because this will enable more information to be extracted from each experiment. Here we present a modification of the cluster analysis proposed by Roland et al. (Human Brain Mapping 1: 3-19, 1993). A covariance model is used to test hypotheses for each voxel. The generated statistical images are searched for the largest clusters. From the same data set noise images are generated. For each of these noise images the autocorrelation function is estimated. These estimates are subsequently used to generate simulated noise images, from which a distribution of cluster sizes is derived. The derived distribution is used to estimate probabilities for the clusters detected in the statistical images generated by testing the hypothesis. This presented method is shown to be specific and is further compared with SPM96 and the nonparametric method of Holmes et al. (J. Cereb. Blood Flow Metab. 16: 7-22, 1996).

Artifacts↗

PubMed1996

Neuroimaging for differentiating vascular from Alzheimer's dementias.

Recent advances in the clinical and neuroimaging features of vascular dementia (VAD) versus Alzheimer type dementia (DAT) are described. The lacunar type of VAD, which is often accompanied by silent strokes and a progressive course, is easily confused with DAT. Measurements of cerebral blood flow (CBF) and metabolism (CMR) displayed as brain maps, identify VAD from DAT because of the multifocal and often subcortical nature of the infarcts in VAD, which are strikingly different from the diffuse cortical reductions of CBF and CMR in DAT. Thus, neuroimaging is important for establishing the diagnosis in these two most common forms of dementia in the elderly. A dramatic method for separating VAD from DAT is by utilizing the noninvasive acetazolamide test and xenon contrast CT scanning for measuring the cerebral vasomotor capacitance. In DAT the vasodilator reserve is increased due to the law of initial values. In VAD it is absent or severely blunted so that the differences between the two underlying causes of the dementias become readily apparent.

Aged↗

PubMed2002

Anatomy based research in neurosurgery.

The Anatomy Based Research in Neurosurgery is an important part of Applied Neuroanatomy that mainly concerns neurosurgical procedures and related problems, namely neuroimaging, brain mapping and surgical techniques. This includes a wide variety of research fields such as 2-D and 3-D structure visualization and referencing (stereotaxy), intraoperative imaging cartography and targeting (neuronavigation), as well as microsurgical, functional and endoscopic anatomy. The methods involved in this investigation regard predominantly microsurgical proceedings and morphological variability studies, both on living or post-mortem material (the strict neuroimaging techniques remaining a main tool for radiologists). The present paper provides an overview of the main techniques of neuroanatomical research applied to neurosurgery. Their major indications and requirements are described and discussed. Special attention is paid to some anatomical techniques such as microdissection and serial sectioning as well as 2-D and 3-D image procedures that are explained in detail.

Brain↗

PubMed2004

Distinct brain activation patterns for human maximal voluntary eccentric and concentric muscle actions.

Eccentric muscle contractions generate greater force at a lower level of activation and subject muscles to more severe damage than do concentric actions. A recent investigation has revealed that electroencephalogram (EEG)-derived movement-related cortical potential (MRCP) is greater and occurs earlier for controlling human eccentric than concentric submaximal muscle contractions. However, whether the central nervous system (CNS) control signals for high-intensity or maximal-effort eccentric movements differ from those for concentric actions is unknown. The purpose of this study was to determine whether the MRCP signals differ between the two types of maximal-effort contractions. Eight volunteers performed 40 maximal voluntary eccentric and 40 maximal voluntary concentric elbow flexor contractions on a Kin-Com isokinetic dynamometer. Scalp EEG signals (62 channels) were measured along with force, joint angle, and electromyographic (EMG) signals of the performing muscles. MRCP-based two-dimensional brain maps were created to illustrate spatial and temporal distributions of the MRCP signals. Although the level of elbow flexor muscle activity was lower during eccentric than concentric movements, MRCP-indicated cortical activation was greater both in amplitude and area dimension for the eccentric task. Detailed comparisons of individual electrode signals suggested that eccentric movements needed a significantly longer time for early preparation and a significantly greater magnitude of cortical activity for later movement execution. The extra preparation time and higher amplitude of activation may reflect CNS activities that account for the higher risk of injury, higher degree of movement difficulty, and unique motor unit activation pattern associated with maximal-level eccentric muscle actions.

Adult↗

PubMed2004

3D topographic study of the diode laser evoked potentials (LEPs) to painful stimulation of the trigeminal sensory area.

A diode laser attached with an optic fiber is flexible and adequate for painful cutaneous stimulation. The brain potentials elicited by diode laser stimulation reflect activation of thin-myelinated afferent fibers. This study examined the use of diode laser evoked potentials (LEPs) elicited from the left/right ophthalmic and maxillary branch of the trigeminal nerve. Twelve males (age: 26.3 +/- 4.5) participated in this study. A 20W diode laser (980 nm wavelength, 0.5 mm spot diameter) was used for stimulation. The stimulus duration was 250 ms, and inter-stimulus interval was 5 sec. The stimulus intensity was tailored to each individual eliciting mild pinprick pain. Fifty stimuli were delivered to each of the four stimulation sites. Atotal of 32 channels EEG (-1024 ms to 2048 ms) was recorded. The grand mean averages were evaluated using 3D topographic brain maps. Repeated measure ANOVA was used for statistical comparisons. Ten out of the 12 subjects resulted in a vertex component with major activations described as a negativity (-6.15 to -7.52 microV) peaking around 370 ms and a positivity (14.22 to 16.29 microV) peaking around 500 ms. This vertex potential reflected activation of the thin A-delta fiber innervating thermal and nociceptive receptors in the face. This vertex potential to diode laser stimulation may be applicable in clinical studies in patients with neurological affections of the trigeminal nerves or nucleus e.g. before and after surgery. The diode laser may be very useful for clinical neurophysiological purposes due to its applicability and user-friendly function.

Adult↗

PubMed1981

Tinnitus: development of a neurophysiologic correlate.

Although tinnitus severely afflicts 7.2 million Americans, the pathophysiology of this problem remains obscure because there presently exists no good animal model in which to study the phenomenon. We have examined changes in activity in the guinea pig auditory pathway using an autoradiographic method of functional brain mapping after short-term and long-term cochlear ablations which can, in humans, initiate the occurrence of tinnitus. With this method we have observed a reduction in activity in various nuclei in the auditory pathway between 4 hrs and 10 days after unilateral cochlear ablation. In contrast to these findings we have found a return of activity in these same nuclei if they are observed from 12 to 48 days following the lesion. These preliminary data suggest that this return of activity in the absence of sensory input may be a valid experimental analogue for tinnitus in humans. Such evidence for auditory plasticity may represent a significant first step toward understanding this common and profound otologic symptom.

Animals↗

PubMed2004

Affine registration: a comparison of several programs.

Several registration programs with an affine model for the displacement field were tested on various 2D and 3D MRI of the same modality. The following programs were considered: AIR 3.0 (Woods, J. Comp. Assist. Tomogr, 22(1): 139-152, 1998), COCGV (Ostuni, JMRI, 7(2): 410-415, 1997), FLIRT (Jenkinson, Med. Image Analysis, 5(2): 143-156, 2001), Intramodal Registration (Thevenaz, IEEE Trans. Image Proc., 7(1): 27-41, 1998), SPM (Friston, Human Brain Mapping, 2: 165-189, 1995), and Patch Algorithm (Zhilkin, MRI 18(9): 1143-1150, 2000). Although some of these programs can perform multimodal registration, none was used in such a mode. This paper attempts a fair comparison of the performance of the Patch Algorithm with other programs. However, different settings of the programs' parameters may further improve the quality of the registration and/or change execution speed. The registered images, the CPU time required to perform the registration, and the error between the registered and reference images, are presented. Most of the programs give comparable accuracies of registration, but their execution times vary considerably. In general the AIR and Patch Algorithm require the least time. The Patch Algorithm can be easily parallelizable on a multi-processor computer.

Algorithms↗

PubMed2004

Magnetoencephalography indicates finger motor somatotopy.

The existence or non-existence of fine-scale motor somatotopy of the hand is a fundamental problem with regard to the functioning of the human brain. In contrast to seldom contradicted early twentieth century descriptions of activation overlap, descriptions of finger motor somatotopy faced disagreement. Recent blood-flow-related brain mapping data achieved with functional magnetic resonance imaging (fMRI) argue in favour of fine-scale somatotopy. However, considerable discrepancies between blood oxygen-level-dependent fMRI activations and intracortically recorded neuronal activity have been reported and it is unclear whether the blood flow results truly reflect the neuronal situation. We have used recent advances in magnetoencephalography to detect signals deriving directly from neuronal tissue. Besides replication of the overlap aspect, we found statistically significant evidence for the existence of a somatotopic aspect of human hand motor representation when comparing the fifth and first finger motor dipoles along the superior-inferior axis. The average location of the fifth finger was found to be 2.31 mm superior to the first finger.

Adult↗

PubMed1994

Quantitative EEG in children with headache.

The object of this work is to determine if Brain Mapping can reveal significant differences between a normal control group and a group whose members suffer from one of three types of headache: tension-type, migraine with aura and migraine without aura. Both groups were formed by children aged between 6 and 14; the latter were undergoing no treatment and were in a headache-free phase. Results demonstrate that there are no significant differences between the control group and the tension-type headache group. Neither were differences found in migraine without aura group but in migraine with aura there was an increase of the theta/alpha ratio in the temporal posterior and occipital zones. This ratio could be used as a neurophysiological indicator in the evolution of the migraine with aura pathology.

Adolescent↗

PubMedDate not supplied

The Digital Anatomist distributed framework and its applications to knowledge-based medical imaging.

The domain of medical imaging is anatomy. Therefore, anatomic knowledge should be a rational basis for organizing and analyzing images. The goals of the Digital Anatomist Program at the University of Washington include the development of an anatomically based software framework for organizing, analyzing, visualizing and utilizing biomedical information. The framework is based on representations for both spatial and symbolic anatomic knowledge, and is being implemented in a distributed architecture in which multiple client programs on the Internet are used to update and access an expanding set of anatomical information resources. The development of this framework is driven by several practical applications, including symbolic anatomic reasoning, knowledge based image segmentation, anatomy information retrieval, and functional brain mapping. Since each of these areas involves many difficult image processing issues, our research strategy is an evolutionary one, in which applications are developed somewhat independently, and partial solutions are integrated in a piecemeal fashion, using the network as the substrate. This approach assumes that networks of interacting components can synergistically work together to solve problems larger than either could solve on its own. Each of the individual projects is described, along with evaluations that show that the individual components are solving the problems they were designed for, and are beginning to interact with each other in a synergistic manner. We argue that this synergy will increase, not only within our own group, but also among groups as the Internet matures, and that an anatomic knowledge base will be a useful means for fostering these interactions.

Anatomy↗

PubMed2000

Network analysis of brain activations in working memory: behavior and age relationships.

Forty-six middle-aged female subjects were scanned using functional Magnetic Resonance Imaging (fMRI) during performance of three distinct stages of a working memory task-encoding, rehearsal, and recognition-for both printed pseudowords and visual forms. An expanse of areas, involving the inferior frontal, parietal, and extrastriate cortex, was active in response to stimuli during both the encoding and recognition periods. Additional increases during memory recognition were seen in right prefrontal regions, replicating a now-common finding [for reviews, see Fletcher et al. (1997) Trends Neurosci 20:213-218; MacLeod et al. (1998) NeuroImage 7:41-48], and broadly supporting the Hemispheric Encoding/Retrieval Asymmetry hypothesis [Tulving et al. (1994) Proc Natl Acad Sci USA 91:2016-2020]. Notably, this asymmetry was not qualified by the type of material being processed. A few sites demonstrated higher activity levels during the rehearsal period, in the absence of any new stimuli, including the medial extrastriate, precuneus, and the medial temporal lobe. Further analyses examined relationships among subjects' brain activations, age, and behavioral scores on working memory tests, acquired outside the scanner. Correlations between brain scores and behavior scores indicated that activations in a number of areas, mainly frontal, were associated with performance. A multivariate analysis, Partial Least Squares [McIntosh et al. (1996) NeuroImage 3:143-157, (1997) Hum Brain Map 5:323-327], was then used to extract component effects from this large set of univariate correlations. Results indicated that better memory performance outside the scanner was associated with higher activity at specific sites within the frontal and, additionally, the medial temporal lobes. Analysis of age effects revealed that younger subjects tended to activate more than older subjects in areas of extrastriate cortex, medial frontal cortex, and the right medial temporal lobe; older subjects tended to activate more than younger subjects in the insular cortex, right inferior temporal lobe, and right inferior frontal gyrus. These results extend recent reports indicating that these regions are specifically involved in the memory impairments seen with aging.

Adult↗

PubMed2005

EEG patterns associated with nitrogen narcosis (breathing air at 9 ATA).

INTRODUCTION: The narcotic effect of nitrogen impairs diver performance and limits dive profiles, especially for deep dives using compressed air. It would be helpful to establish measurable correlates of nitrogen narcosis. METHODS: The authors observed the electroencephalogram (EEG) of 10 subjects, ages 22-27 yr, who breathed air during a 3-min compression to a simulated depth of 80 msw (9 ATA). The EEG from a 19-electrode cap was recorded for 20 min while the subject reclined on a cot with eyes closed, first at 1 ATA before the dive and again at 9 ATA. Signals were analyzed using Fast Fourier Transform and brain mapping for frequency domains 0-4 Hz, 4-7 Hz, 7-12 Hz, and 12-15 Hz. Student's paired t-test and correlation tests were used to compare results for the two conditions. RESULTS: Two EEG patterns were observed. The first was an increase in delta and theta activity in all cortical regions that appeared in the first 2 min at depth and was related to exposure time. The second was an increase in delta and theta activity and shifting of alpha activity to the frontal regions at minute 6 of breathing air at 9 ATA and was related to the narcotic effects of nitrogen. DISCUSSION: If confirmed by studies with larger case series, this EEG pattern could be used to identify nitrogen narcosis for various gas mixtures and prevent the dangerous impact of nitrogen on diver performance.

Adult↗

PubMed2005

Neuroanatomical predictors of response to donepezil therapy in patients with dementia.

BACKGROUND: Patients with dementia of the Alzheimer type (DAT) respond variably to treatment with acetylcholinesterase inhibitors. OBJECTIVE: To determine whether measures of hippocampal volume and shape predict the response to donepezil in patients with DAT. DESIGN: T1-weighted, magnetic resonance images were obtained from patients with DAT, who subsequently underwent treatment with donepezil. Brain-mapping algorithms were used to quantify hippocampal volume and shape, and growth curves were used to estimate clinical outcome. SETTING: A referral outpatient center specializing in treatment of dementia. PATIENTS: Thirty-seven patients with very mild or mild DAT received donepezil therapy for up to 4 weeks before magnetic resonance imaging and for 24 to 96 weeks after magnetic resonance imaging. INTERVENTION: Donepezil, 10 mg/d. MAIN OUTCOME MEASURE: Rate of change in the cognitive portion of the Alzheimer's Disease Assessment Scale total scores. RESULTS: Smaller hippocampal volume and inward variation of the lateral and inferomedial portions of the hippocampal surface were correlated with a poorer response to donepezil therapy. CONCLUSIONS: Measures of hippocampal volume and surface variation can be used to predict the response of patients with DAT to the acetylcholinesterase inhibitor donepezil.

Alzheimer Disease↗

PubMed2005

Characteristic functional networks in high- versus low-proficiency second language speakers detected also during native language processing: an explorative EEG coherence study in 6 frequency bands.

An EEG coherence study was performed with a twofold objective: first, to scrutinize the theoretical concept of "cortical efficiency" in connection with second language (L2) acquisition and, second, to detect cooperations between cortical areas in specific frequency bands indicative for highly proficient L2 processing. Two groups differing only in their level of L2 proficiency were contrasted during presentation of natural language videos in English (L2) and German (native language, L1), with explorative coherence analysis in 6 frequency bands (0.5-31.5 Hz). The coherence brain maps revealed more pronounced and widespread increases in coherences in the alpha1-band (8-10 Hz) in low-proficiency than in the high-proficiency L2 speakers. Surprisingly, this difference was obtained also during L1 processing and corroborated for both languages by multivariate permutation tests. These tests revealed additional differences between the low- and the high-proficiency group also for coherences within the beta1- (13-18 Hz) and the beta2-band (18.5-31.5 Hz), again during L2 and L1 processing. Since the same group differences were observed during L1 and L2 processing, our high-proficiency group might have profited from a more generic advantage in language or text processing strategy. This strategic advantage was most evident at alpha1 frequencies, possibly related to a specific way of processing internal mental states (top-down processing).

Acoustic Stimulation↗