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Cortical regulation during the early stage of initiation of voluntary swallowing in humans.

The aim of the present study was to reveal the spatiotemporal relations among cortical regions involved in the initiation of voluntary swallowing in humans using magnetoencephalography (MEG). As a control task, finger extension movement, which is purely voluntary, was also investigated using the same techniques. The swallowing-related activity was distributed widely for 2000 ms before the electromyogram onset of the right suprahyoid muscle; however, the finger-related activity occurred in the late stage of the recording. The cingulate cortex, the insula, and the inferior frontal gyrus were the main loci active prior to swallowing. These cortical loci coincide with those suggested by previous human brain mapping studies that investigated the brain mechanism which controls swallowing. Activation in the cingulate cortex was registered in the early stage of swallowing and could be related to the cognitive process regarding the food being safe to swallow. The activation in the insula lasted for a long time before the initiation of swallowing. This suggests that the long-lasting activation in the insula prior to swallowing is essential for the initiation of swallowing.

Adult↗

An optimized individual target brain in the Talairach coordinate system.

The goal of regional spatial normalization is to remove anatomical differences between individual three-dimensional brain images by warping them to match features of a single target brain. Current target brains are either an average, suitable for low-resolution brain mapping studies, or a single brain. While a single high-resolution target brain is desirable to match anatomical detail, it can lead to bias in anatomical studies. An optimization method to reduce the individual anatomical bias of the ICBM high-resolution brain template (HRBT), a high-resolution MRI target brain image used in many laboratories, is presented. The HRBT was warped to all images in a group of 27 normal subjects. Displacement fields were averaged to calculate the "minimal deformation target" (MDT) transformation for optimization. The greatest anatomical changes in the HRBT, following optimization, were observed in the superior precentral and postcentral gyri on the right, the right inferior occipital, the right posterior temporal lobes, and the lateral ventricles. Compared with the original HRBT, the optimized HRBT showed better anatomical matching to the group of 27 brains. This was quantified by the improvements in spatial cross-correlation and between the group of brains and the optimized HRBT (P < 0.05). An intended use of this processing is to create a digital volumetric atlas that represents anatomy of a normal adult brain by optimizing the HRBT to the group consisting of 100+ normal subjects.

Adult↗

Topographic distribution of the periodic discharges in Creutzfeldt-Jakob disease (CJD).

A characteristic EEG abnormality in patients with Creutzfeldt-Jakob disease (CJD) consists of periodic high voltage bilateral diphasic or triphasic sharp waves widely distributed over both hemispheres. The mechanism underlying these electrographic manifestations is, however, unclear. To increase our understanding of these phenomena, we have employed the technique of microcomputer brain mapping, to analyze the electrical fields of the bilaterally-distributed complexes in four patients with CJD. Ten generalized discharges were studied in each patient. The EEG analysis demonstrated variability in the area of onset as well as the field maxima between the different complexes among patients as well as between discharges in each patient. The generalized pattern seen in routine EEG was clearly shown on brain mapping to be not strictly generalized from onset, nor bilaterally symmetrical. These findings may suggest multifocal areas of onset of the generalized discharges, or alternating pathways of activation of the cortical areas by a subcortical pacemaker.

Aged↗

Virtual 10-20 measurement on MR images for inter-modal linking of transcranial and tomographic neuroimaging methods.

It is important to create a link between stereotaxic coordinates and head-surface-based positioning systems in order to share data between tomographic and transcranial brain mapping studies. In our previous studies, we established the probabilistic correspondence of the international 10-20 positions to the standard stereotaxic coordinate systems and made a reference database. However, its expansion required the physical marking of the 10-20 positions and the subsequent acquisition of MR images. To avoid such tedious procedures, we developed a virtual 10-20 measurement algorithm that can be applied to re-analyze any structural MR image that covers the whole head. As in the physical 10-20 measurements, with the reference points given, the algorithm automatically determines each 10-20 position step by step. Using the virtual 10-20 measurement method, we re-analyzed the MR images of 17 healthy subjects for whom we had determined 10-20 positions by physical marking in our previous study. The acquired 10-20 positions were normalized to the Montreal Neurological Institute (MNI) stereotactic coordinates and compared with the positions previously determined by physical measurements. 10-20 positions determined using the virtual and physical methods were roughly consistent. Average standard deviations for virtual and physical methods were 7.7 mm and 9.0 mm, respectively. There was a systematic shift in the virtual method, likely due to the absence of hair interference. We corrected the shift with affine transformation. The virtual 10-20 measurement method proved to be an effective alternative to physical marking. This method will serve as an essential tool for expanding the reference database and will further strengthen the link between tomographic and transcranial brain mapping methods.

Adult↗

Paradoxical scalp lateralization of the P100 cognitive somatic potential in humans: a magnetic field study.

In somatic selective attention, electrical brain mapping disclosed a P100 cognitive electrogenesis with a scalp field paradoxically lateralized ipsilaterally to the target finger stimulus. We used 64 sensors magnetoencephalography (MEG) and source localization software in six normal humans to identify the P100 neural generator. Calculated dipole sources for P100 were iteratively compared with the recorded MEG data. The equivalent dipole at somatic P100 latency was located in the parietal lobe contralateral to the finger stimulus and had an oblique positive gradient pointing towards the ipsilateral side, thus explaining the paradoxical positivity in electrical brain mapping. It is suggested that the somatic P100 is generated in parietal area 7b which indeed appears to be specialized for cognitive processing within the somatic modality rather than for multimodal association.

Brain Mapping↗

Combined functional magnetic resonance imaging and transcranial magnetic stimulation evidence of ipsilateral motor pathway with congenital brain disorder: a case report.

We present the case of 28-year-old man with schizencephaly who had mild left hemiparesis with mirror movement. Brain mapping using functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) for both hand muscles was done to evaluate his neurologic state. Motor evoked potential (MEP) from both abductor pollicis brevis (APB) muscles was obtained simultaneously. fMRI showed that the left primary sensorimotor cortex became active when the right fingers performed the flexion-extension exercise. The left primary sensorimotor cortex, left prefrontal area, and both supplementary motor areas were activated with flexion-extension exercise of the left hand. Brain mapping for both APB muscles using TMS showed that no MEP was evoked in the right hemisphere, but a APB total of 5 sites were evoked in the left hemisphere simultaneously. The optimal scalp site for both APB muscles was present at the same site. The MEPs of both muscles which were evoked by stimulation of the optimal scalp site, showed similar latencies, amplitudes, and figures of potential. The similarities in both MEPs and the same optimal scalp site support the assumption that MEPs of both APB muscles are produced by the corticospinal tract originating from the same motor cortex. Our results showed that the ipsilateral motor pathway extended from the unaffected left hemisphere to both hand muscles. This finding may reflect functional reorganization of motor area in a patient with congenital brain disorder.

Adult↗

Conventional and quantitative EEG in the diagnosis of delirium among the elderly.

This study was performed to determine whether an admission quantitative EEG (QEEG) could assist in the differential diagnosis of encephalopathy among a group of elderly subjects with delirium, dementia, and delirium coexistent with dementia. Thirty four subjects from 57 to 93 years had standard 17-channel EEG and quantitative EEG studies, using a linked-ear reference. EEGs were independently rated by two electroencephalographers blind to clinical diagnosis, using conventional criteria to assess the degree of encephalopathy. Brain maps were scored by a scale developed by the authors. Numerical data examined included mean posterior dominant frequency, absolute and relative power in the delta, theta and alpha bands, and slow-wave ratios. The grouping of experimental subjects was by the discharge diagnosis, made using DSM-III-R criteria. Stepwise discriminant analysis was performed to determine which EEG and QEEG variables were best able to distinguish cases. Variables which collectively distinguished normal from encephalopathic records were Mini-Mental State Examination scores and relative power in the alpha frequency band. Variables which collectively distinguished delirium from dementia were EEG theta activity, relative power in delta, and brain map rating. The results suggest that cross-sectional QEEG study is potentially useful in the early differential diagnosis of encephalopathy, and that the variables which distinguish normal from encephalopathic patients might differ from the variables which distinguish delirium from dementia.

Aged↗

The cerebral response to electrical stimuli in the oesophagus is altered by increasing stimulus frequencies.

Recording of cerebral evoked responses (EP) allows the assessment of visceral afferent pathways and gut-brain communication, but the optimal stimulation parameters remain to be established. The present study determined the optimal stimulation frequency of electrical stimulation of the oesophagus to elicit EP responses. In 13 healthy male volunteers (24.1 +/- 5.9 years), a 5 mm stainless-steel electrode was placed in the distal oesophagus for electrical stimulation (ES). EP were recorded from 21 scalp electrodes placed according to the 10/20 International system. ES (15 mA, 200 microseconds) were delivered in repeated series of 24 stimuli. Stimulus frequency was randomly altered in different series using a pseudologarithmic range (0.1, 0.2, 0.3, 0.5, and 1 Hz). Two series of stimuli were applied using each stimulation frequency. Two-dimensional topographic brain maps were created using interpolation techniques at each stimulation frequency. With increasing stimulus frequency, a significant and progressive decrease of EP amplitudes was observed between frequencies of 0.1 Hz and 1.0 Hz (P1/N2: 7.6 +/- 1.2 vs 1.4 +/- 0.3* microV, N2/P2: 17.2 +/- 1.7 vs 4.6 +/- 0.4* microV, P2/N3: 6.9 +/- 0.7 vs 4.2 +/- 0.5* microV; * = P < 0.05). In addition, there was a significant shortening of the mean peak latency of the intercalated P2 peak (P < 0.0005), with a similar trend for the P3 peak (P < 0.06), with increasing stimulus frequency from 0.1-1.0 Hz. Topographic brain maps localized the maximal early peaks (N1,P1.N2) in the paracentral cortical region (C3, Cz, C4), whereas the later peaks (P2 to P3) were symmetrically spread over the centroparietal and temporal regions (Cz, Pz, T5, T4). There was no difference in the cortical location of maximal EP amplitudes with increasing stimulus frequency. In conclusion, there is a clear relationship between stimulus frequency and amplitude of EP, suggesting rapid attenuation of the cerebral autonomic neural responses with increased electrical stimulation frequency. The effect of increased frequency on peak latencies suggests an alteration of stimulus processing in the thalamocortical region due to an altered perception of stimuli. Early EP peaks originate from basal structures of primarily the dominant hemisphere, while later peaks are localized in centroparietal cortical regions.

Adult↗

One-year dynamic follow-up of patients with reversible ischaemic neurological deficit using quantitative electroencephalography.

The present study was designed to assess the relative value of sEEG and qEEG with brain mapping in the diagnosis of patients with reversible ischaemic neurological deficit (RIND) and the feasibility of these techniques as well as their diagnostic yield in the detection of focal and diffuse changes reflecting the evolution and predicting the prognosis of stroke lesions. Standard (sEEG) and quantitative EEGs (qEEGs) were recorded over a period of one year in 32 patients, aged 40 to 75 years, from a cohort of 54 patients (17 female and 37 male, median age 62 +/- 29.6 years) with a first-ever RIND. A total of 104 sEEGs and 118 qEEGs were performed during the one-year follow-up period. Normal sEEGs were 60 recordings (57.69%) whereas poorly defined low-voltage activity was present in 44 recordings (42.31 +/- 7.50%). No focal changes or asymmetry were found on sEEG. The observed changes in background activity were most probably due to the underlying cerebrovascular disease. The recordings were normal in 72 qEEGs (61%) whereas in 46 qEEGs (39.98 +/- 7.10%) focal changes were detected. Out of the total of 118 recordings with evidence of focal changes in spectrum power increases were found in 91.28% and decreases--in 8.72%, predominantly in the alpha-theta spectrum band. The incidence and localization pattern of the focal findings changed over time. At the beginning site and side were not relevant. The proportion of frequent and unpredictable instability in the symptomatic hemisphere changes was greater immediately following the incident as compared with the changes in the asymptomatic hemisphere, i.e. the discordance increased with the increase in time elapsed since the acute stage. The reverse was true concerning the end of the study period. The importance and the place of sEEG and qEEG with brain mapping in the diagnosis and followup of lesions in RIND patients are critically evaluated.

Adult↗

Atlas-assisted localization analysis of functional images.

OBJECTIVE: This paper introduces a method for localization analysis of functional images assisted by a brain atlas. The usefulness of the system developed, based on this method, is analyzed for human brain mapping and neuroradiology. MATERIALS AND METHODS: We use an enhanced and extended electronic Talairach-Tournoux brain atlas, containing segmented and labeled subcortical structures, Brodmann's areas, and gyri. The brain atlas serves as a tool for anatomy referencing, segmentation, labeling, registration, and providing 3D anatomical relationships. The process of localization analysis is decomposed into five steps: data loading, feature extraction, data normalization, identification and editing of loci, and getting labels and values. This analysis is supported by near real-time data-to-atlas warping based on the Talairach transformation. Metanalysis is enabled by merging the current and external lists of activation loci. RESULTS: We have designed, developed, tested, and deployed a commercial system for atlas-assisted localization analysis of functional images. This is the first system where an electronic version of the Talairach-Tournoux brain atlas is used interactively for analysis of functional images. This system runs on personal computers and provides functions for a rapid normalization of anatomical and functional volumetric data, data segmentation and labeling, readout of Talairach coordinates, and data display. It also is empowered with several unique features including: interactive warping facilitating fine tuning of the data-to-atlas fit, a backtracking mechanism to compensate for missing landmarks and enhancing the outcome of the overall process of data analysis, navigation on the triplanar formed by the data and the atlas, multiple-images-in-one display with atlas-anatomy-function blending, a fast locus-controlled generation of results, editing of loci, multiple label display, and saving and reading of loci. The system normalizes a single image in near real-time (0.7 s), so analysis of anatomical and functional datasets can be done on-the-fly regardless of the number of slices. The same task performed by the state-of-the-art non-linear registration methods may require up to several days. CONCLUSIONS: The system is a useful tool for atlas-assisted localization analysis and a helpful adjunct to function/location metanalysis in human brain mapping research. It is also a step forward in bringing the atlas and the clinical data together within a practical and powerful solution that is fast and flexible, yet low-cost and affordable.

Anatomy, Artistic↗

ERP evidence of a dichotic left-ear deficit in some dyslexic children.

Children with and without behavioral dichotic left-ear deficits participated in an event-related potential study with quasidichotic presentations of familiar fairy tale segments. Electrical activity was recorded from the scalp while the children listened for semantically and/or syntactically anomalous words from either the right side or the left side while competing segments of the fairy tale were simultaneously presented from the opposite side. Latencies and amplitudes were averaged for each target condition within the group with dichotic left-ear deficits (LED) and the group with normal dichotic listening performance (WNL). Individual global field power waveforms and topographic brain maps were generated for the average response in each of the two listening conditions, target right and target left. Cross-correlations were performed on the grand averaged global field power waveforms to measure the degree of synchrony between target right and target left responses in both groups. Integration functions were performed to compare the accumulated sum of voltages during target (right and left) and control (right and left) conditions. WNL children produced typical ERP responses to the target words in both target right and target left conditions. Responses from LED children were at delayed latencies in the target left condition and were at reduced amplitudes in both target conditions. Topographic brain maps revealed more lateralized scalp distributions and greater activation of frontal regions in LED children in the target left condition. Cross-correlational and integration function results demonstrated interaural asymmetries in responses from the LED children. Overall results suggest that slowed neural conduction times, poor interhemispheric transfer of neural activity, and a failure to suppress competing information arriving at the right ear may be involved in poor left-sided processing in children with behavioral left-ear dichotic deficits.

Analysis of Variance↗

Motivation and synthesis of the FIAC experiment: Reproducibility of fMRI results across expert analyses.

The Functional Imaging Analysis Contest (FIAC) culminated in the FIAC Workshop held at the 11th Annual Meeting of the Organization for Human Brain Mapping in Toronto in 2005. This special issue summarizes various analyses used by contestants with a single functional magnetic resonance imaging (fMRI) study, a cortical-language study using sentence repetition. The results from the cognitive neuroscientists who developed the test-base language study, and report their data analysis, are complemented by expert analyses of the same test-base data by most of the major groups actively developing fMRI software packages. Analyses include many variants of the general linear model (GLM), cutting-edge spatial- and temporal-wavelets, permutation-based, and ICA approaches. A number of authors also include surface-based approaches. Several articles describe the important emerging areas of diagnostics for GLM analysis, multivariate predictive modeling, and functional connectivity analysis. While the FIAC did not achieve all of its goals, it helped identify new activation regions in the test-base data, and more important, through this special issue it illustrates the significant methods-driven variability that potentially exists in the literature. Variable results from different methods reported here should provide a cautionary note and motivate the Human Brain Mapping community to explore more thoroughly the methodologies they use for analyzing fMRI data.

Brain Mapping↗

Mapping motor inhibition: conjunctive brain activations across different versions of go/no-go and stop tasks.

Conjunction analysis methods were used in functional magnetic resonance imaging to investigate brain regions commonly activated in subjects performing different versions of go/no-go and stop tasks, differing in probability of inhibitory signals and/or contrast conditions. Generic brain activation maps highlighted brain regions commonly activated in (a) two different go/no-go task versions, (b) three different stop task versions, and (c) all 5 inhibition task versions. Comparison between the generic activation maps of stop and go/no-go task versions revealed inhibitory mechanisms specific to go/no-go or stop task performance in 15 healthy, right-handed, male adults. In the go/no-go task a motor response had to be selectively executed or inhibited in either 50% or 30% of trials. In the stop task, the motor response to a go-stimulus had to be retracted on either 50 or 30% of trials, indicated by a stop signal, shortly (250 ms) following the go-stimulus. The shared "inhibitory" neurocognitive network by all inhibition tasks comprised mesial, medial, and inferior frontal and parietal cortices. Generic activation of the go/no-go task versions identified bilateral, but more predominantly left hemispheric mesial, medial, and inferior frontal and parietal cortices. Common activation to all stop task versions was in predominantly right hemispheric anterior cingulate, supplementary motor area, inferior prefrontal, and parietal cortices. On direct comparison between generic stop and go/no-go activation maps increased BOLD signal was observed in left hemispheric dorsolateral prefrontal, medial, and parietal cortices during the go/no-go task, presumably reflecting a left frontoparietal specialization for response selection.

Adult↗

Accuracy of stereotaxic positioning of transcranial magnetic stimulation.

In cognitive neuroscience, optically tracked frameless stereotaxic navigation has been successfully used to precisely guide transcranial magnetic stimulation (TMS) to desired cortical areas for brain-mapping purposes. Thereby, potential sources of imprecision are the fixation of a reference frame to the head of the subject and the referencing procedure according to certain landmarks (LM). The aim of our study was to evaluate the accuracy of frameless stereotaxic coil positioning in a standard experimental setting. A parameter for accuracy is the reproducibility of LM coordinates. In order to test the stability of the referencing for stereotaxic positioning within a single TMS session (within-session stability), the coordinates of six predefined facial LM in nine subjects were recorded first after the initial registration and second after a 20 minutes TMS session. The two sets of coordinates were then compared. The reliability of the positioning coordinates between different TMS sessions (inter-session repeatability) was addressed by registering the subjects LM coordinates in two independent TMS sessions. The variance of the recorded coordinates was analyzed. Altogether, LM were registered 1728 times (192 measures per subject). Within-session stability: The mean Euclidean distance (MED) between the LM position coordinates before and after a TMS session was 1.6 mm, when pooling over all LM. Inter-session repeatability: The MED between the LM positions recorded after the reference procedures of two different sessions showed an average deviation of 2.5 mm. In conclusion, optically tracked frameless stereotaxic coil positioning is from the technical viewpoint of high stability and repeatability. It is therefore a precise method for TMS brain mapping studies or for repeated TMS treatments, with the need of topographically exact stimulation.

Adult↗

Quantitative functional imaging of the brain: towards mapping neuronal activity by BOLD fMRI.

Quantitative magnetic resonance imaging (MRI) and spectroscopy (MRS) measurements of energy metabolism (i.e. cerebral metabolic rate of oxygen consumption, CMR(O2)), blood circulation (i.e. cerebral blood flow, CBF, and volume, CBV), and functional MRI (fMRI) signal over a wide range of neuronal activity and pharmacological treatments are used to interpret the neurophysiologic basis of blood oxygenation level dependent (BOLD) image-contrast at 7 T in glutamatergic neurons of rat cerebral cortex. Multi-modal MRI and MRS measurements of CMR(O2), CBF, CBV and BOLD signal (both gradient-echo and spin-echo) are used to interpret the neuroenergetic basis of BOLD image-contrast. Since each parameter that can influence the BOLD image-contrast is measured quantitatively and separately, multi-modal measurements of changes in CMR(O2), CBF, CBV, BOLD fMRI signal allow calibration and validation of the BOLD image-contrast. Good agreement between changes in CMR(O2) calculated from BOLD theory and measured by (13)C MRS, reveals that BOLD fMRI signal-changes at 7 T are closely linked with alterations in neuronal glucose oxidation, both for activation and deactivation paradigms. To determine the neurochemical basis of BOLD, pharmacological treatment with lamotrigine, which is a neuronal voltage-dependent Na(+) channel blocker and neurotransmitter glutamate release inhibitor, is used in a rat forepaw stimulation model. Attenuation of the functional changes in CBF and BOLD with lamotrigine reveals that the fMRI signal is associated with release of glutamate from neurons, which is consistent with a link between neurotransmitter cycling and energy metabolism. Comparisons of CMR(O2) and CBF over a wide dynamic range of neuronal activity provide insight into the regulation of energy metabolism and oxygen delivery in the cerebral cortex. The current results reveal the energetic and physiologic components of the BOLD fMRI signal and indicate the required steps towards mapping neuronal activity quantitatively by fMRI at steady-state. Consequences of these results from rat brain for similar calibrated BOLD fMRI studies in the human brain are discussed.

Animals↗

Immunohistochemical mapping of brain triiodothyronine reveals prominent localization in central noradrenergic systems.

Many lines of evidence support a close association between thyroid hormones and noradrenergic systems in peripheral tissues. However, there is little certainty regarding interactions of the two systems in brain. We now report that triiodothyronine is concentrated in both nuclei and projection sites of central noradrenergic systems. Immunohistochemical mapping of the hormone revealed the following: (1) Locus coeruleus and all other noradrenergic cell groups identified were the most prominently labeled neural centers in the brain. (2) The hormone was also concentrated in the widely dispersed targets of noradrenergic projections. (3) Triiodothyronine labeling in noradrenergic target cells was most prominent over the cell nuclei, indicating that the hormone was bound to its receptors. Therefore, targets of noradrenergic innervation should be responsive to triiodothyronine. (4) Unlike that in noradrenergic target cells, triiodothyronine staining was decidedly perikaryal in locus coeruleus (A-6) and the other A-1 to A-7 cell groups; the staining pattern in locus coeruleus cytosol and processes was heavy, clumped and similar to that seen in contiguous sections immunostained for tyrosine hydroxylase. Results of radio-immunoassay, immunoabsorption and pharmacological tests demonstrated the specificity of the antibody for triiodothyronine and ruled against cross-reactivity with norepinephrine or its metabolites as the basis for the staining reactions. Although other possibilities consistent with these new observations are given consideration, it appears that the structure and activity of central noradrenergic systems may be major determinants of triiodothyronine distribution patterns and actions in brain. If the noradrenergic system processes both triiodothyronine and norepinephrine and conducts them both to nerve cell groups receiving its terminal arborizations, specific postsynaptic receptors would be available for transduction of both sets of messages. The evidence provides a morphological basis for earlier proposals that triiodothyronine may play a neuromodulatory or neurotransmitter role in the adrenergic nervous system.

Animals↗

Expression of c-fos protein in brain: metabolic mapping at the cellular level.

The proto-oncogene c-fos is expressed in neurons in response to direct stimulation by growth factors and neurotransmitters. In order to determine whether the c-fos protein (Fos) and Fos-related proteins can be induced in response to polysynaptic activation, rat hindlimb motor/sensory cortex was stimulated electrically and Fos expression examined immunohistochemically. Three hours after the onset of stimulation, focal nuclear Fos staining was seen in motor and sensory thalamus, pontine nuclei, globus pallidus, and cerebellum. Moreover, 24-hour water deprivation resulted in Fos expression in paraventricular and supraoptic nuclei. Fos immunohistochemistry therefore provides a cellular method to label polysynaptically activated neurons and thereby map functional pathways.

Animals↗