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PubMed2004

Efficacy assessment of cerebral arterial bypass surgery using statistical parametric mapping and probabilistic brain atlas on basal/acetazolamide brain perfusion SPECT.

UNLABELLED: The efficacy of cerebral arterial bypass surgery was assessed on brain perfusion SPECT using statistical parametric mapping (SPM) and a probabilistic brain atlas. METHODS: Fifteen patients with ischemia in the internal carotid artery (ICA) territory and 21 age-matched healthy volunteers were enrolled. (99m)Tc-HMPAO basal/acetazolamide brain perfusion SPECT was performed 2 wk before and after bypass surgery and also on a healthy control group. Using SPM analysis, group comparisons were made between pre- and postoperative SPECT for each basal/acetazolamide image, and improvements of perfusion and perfusion reserve were assessed. The number of significant voxels on the SPM analysis was defined as the extent of ischemia. With the use of the probabilistic brain atlas, the counts for the cerebral lobes and the ICA territory were automatically calculated for each image and compared. RESULTS: The group comparisons by SPM between patients and healthy volunteers showed a significant improvement in general perfusion status in the ICA territory. The improvement in perfusion reserve was more extensive than the improvement in perfusion. The extent of ischemia was also significantly decreased after surgery (1,693 +/- 2,604 to 371 +/- 523 voxels in basal images, P = 0.060; 11,879 +/- 6,449 to 5,997 +/- 3,864 voxels in acetazolamide images, P = 0.005). In the analysis using the probabilistic brain atlas, the preoperatively decreased perfusion was normalized after surgery, but a residual decrease in the perfusion reserve was also observed in the ICA territory. The counts in the volume of interest of the ICA territory were significantly improved (38.5 +/- 4.1 to 41.5 +/- 2.7 in basal images, P = 0.024; 34.2 +/- 4.4 to 38.8 +/- 2.9 in acetazolamide images, P = 0.003). One patient showing a decrease in perfusion had a perioperative cerebral infarct. CONCLUSION: Using SPM and a probabilistic brain atlas, the perfusion, the perfusion reserve, and changes in both after cerebral arterial bypass surgery were effectively assessed and correlated well with physiologic reasoning.

Acetazolamide↗
PubMed2006

Effect of spatial smoothing on t-maps: arguments for going back from t-maps to masked contrast images.

Voxelwise statistical analysis has become popular in explorative functional brain mapping with fMRI or PET. Usually, results are presented as voxelwise levels of significance (t-maps), and for clusters that survive correction for multiple testing the coordinates of the maximum t-value are reported. Before calculating a voxelwise statistical test, spatial smoothing is required to achieve a reasonable statistical power. Little attention is being given to the fact that smoothing has a nonlinear effect on the voxel variances and thus the local characteristics of a t-map, which becomes most evident after smoothing over different types of tissue. We investigated the related artifacts, for example, white matter peaks whose position depend on the relative variance (variance over contrast) of the surrounding regions, and suggest improving spatial precision with 'masked contrast images': color-codes are attributed to the voxelwise contrast, and significant clusters (e.g., detected with statistical parametric mapping, SPM) are enlarged by including contiguous pixels with a contrast above the mean contrast in the original cluster, provided they satisfy P < 0.05. The potential benefit is demonstrated with simulations and data from a [11C]Carfentanil PET study. We conclude that spatial smoothing may lead to critical, sometimes-counterintuitive artifacts in t-maps, especially in subcortical brain regions. If significant clusters are detected, for example, with SPM, the suggested method is one way to improve spatial precision and may give the investigator a more direct sense of the underlying data. Its simplicity and the fact that no further assumptions are needed make it a useful complement for standard methods of statistical mapping.

Algorithms↗
PubMed2001

Integration of microstructural and functional aspects of human somatosensory areas 3a, 3b, and 1 on the basis of a computerized brain atlas.

In this study we analyzed structural and functional aspects of the human primary somatosensory areas 3a, 3b, and 1 on the basis of a computerized brain atlas. The approach overcomes many of the problems associated with subjective architectonic parcellations of the cortex and with 'classical" brain maps published in a "rigid" print format. Magnetic resonance (MR) scans were obtained from ten postmortem brains. The brains were serially sectioned at 20 microm, and sections were stained for cell bodies. Areas 3a, 3b, and 1 were delineated statistically on the basis of differences in the laminar densities of neuronal cell bodies. The borders of the areas were topographically variable across different brains and did not match macroanatomical landmarks of the postcentral gyrus. After correction of the sections for deformations due to histological processing, each brain's 3-D reconstructed histological volume and the volume representations of areas 3a, 3b, and 1 were adapted to the reference brain of a computerized atlas and superimposed in 3-D space. For each area, a population map was generated that described, for each voxel, how many brains had a representation of that area. Despite considerable interindividual variability, representations of areas 3a, 3b, and 1 in > or = 50% of the brains were found in the fundus of the central sulcus, in the rostral bank, and on the crown of the postcentral gyrus, respectively. For each area, a volume of interest (VOI) was defined that encompassed that area's representation in > or = 50% of the brains. Despite close spatial relationship in the postcentral gyrus, the three VOIs overlapped by < 1% of their volumes. Changes in regional cerebral blood flow (rCBF) were measured with positron emission tomography when six right-handed subjects discriminated differences in the speed of a rotating brush stimulating the palmar surface of the right hand. With co-registered MR images, the rCBF data were adapted to the same reference brain and superimposed with the microstructural VOIs. Discrimination of moving stimuli, contrasted to rest, increased the rCBF in the VOIs of areas 3b and 1, but not in area 3a. This approach opens up the possibility of (1) defining VOIs of cortical areas which are not based on macroanatomical landmarks but instead on observer-independent cytoarchitectonic mapping of postmortem brains and of (2) determining in these VOIs changes in rCBF data obtained from functional imaging experiments.

Adult↗
PubMed2005

Retinotopic mapping in the human visual cortex using vascular space occupancy-dependent functional magnetic resonance imaging.

Recently, we introduced a new methodology, vascular space occupancy functional magnetic resonance imaging, which detects brain activation on the basis of blood volume changes in parenchymal microvasculature and may provide higher spatial specificity than the blood oxygenation level-dependent method. To study whether this technique can be used for advanced brain mapping applications, we performed retinotopic mapping using alternating horizontal and vertical wedges that stimulate different portions of the visual field. The results using vascular space occupancy functional magnetic resonance imaging showed clear boundaries for V1/V2/VP/V4v in the ventral areas and V1/V2/V3/V3A in the dorsal areas, similar to the maps obtained using blood oxygenation level-dependent functional magnetic resonance imaging. Vascular space occupancy functional magnetic resonance imaging is a useful addition to the other neuroimaging techniques. Disadvantages of vascular space occupancy functional magnetic resonance imaging include lower contrast-to-noise ratio (about 1/3 of that of blood oxygenation level-dependent method) and limited volume coverage (nine slices for TR=3 s).

Adult↗
PubMed2006

Interleaving brain systems for episodic and recognition memory.

Conflicting models persist over the nature of long-term memory. Crucial issues are whether episodic memory and recognition memory reflect the same underlying processes, and the extent to which various brain structures work as a single unit to support these processes. New findings that have resulted from improved resolution of functional brain imaging, together with recent studies of amnesia and developments in animal testing, reinforce the view that recognition memory comprises at least two independent processes: one recollective and the other using familiarity detection. Only recollective recognition appears to depend on episodic memory. Attempts to map brain areas supporting these two putative components of recognition memory indicate that they depend on separate, but interlinked, structures.

Amnesia, Anterograde↗
PubMed2005

Automated 3-D extraction and evaluation of the inner and outer cortical surfaces using a Laplacian map and partial volume effect classification.

Accurate reconstruction of the inner and outer cortical surfaces of the human cerebrum is a critical objective for a wide variety of neuroimaging analysis purposes, including visualization, morphometry, and brain mapping. The Anatomic Segmentation using Proximity (ASP) algorithm, previously developed by our group, provides a topology-preserving cortical surface deformation method that has been extensively used for the aforementioned purposes. However, constraints in the algorithm to ensure topology preservation occasionally produce incorrect thickness measurements due to a restriction in the range of allowable distances between the gray and white matter surfaces. This problem is particularly prominent in pediatric brain images with tightly folded gyri. This paper presents a novel method for improving the conventional ASP algorithm by making use of partial volume information through probabilistic classification in order to allow for topology preservation across a less restricted range of cortical thickness values. The new algorithm also corrects the classification of the insular cortex by masking out subcortical tissues. For 70 pediatric brains, validation experiments for the modified algorithm, Constrained Laplacian ASP (CLASP), were performed by three methods: (i) volume matching between surface-masked gray matter (GM) and conventional tissue-classified GM, (ii) surface matching between simulated and CLASP-extracted surfaces, and (iii) repeatability of the surface reconstruction among 16 MRI scans of the same subject. In the volume-based evaluation, the volume enclosed by the CLASP WM and GM surfaces matched the classified GM volume 13% more accurately than using conventional ASP. In the surface-based evaluation, using synthesized thick cortex, the average difference between simulated and extracted surfaces was 4.6 +/- 1.4 mm for conventional ASP and 0.5 +/- 0.4 mm for CLASP. In a repeatability study, CLASP produced a 30% lower RMS error for the GM surface and a 8% lower RMS error for the WM surface compared with ASP.

Algorithms↗
PubMed2006

Usefulness of SPECT/CT with a hybrid camera for the functional anatomical mapping of primary brain tumors by [Tc99m] tetrofosmin.

The aims of this study were to assess the clinical usefulness of [Tc-99m] tetrofosmin (TF) single photon emission computed tomography (SPECT) and X-ray transmission computed tomography (CT), performed simultaneously with a hybrid imaging device for the functional anatomical mapping of brain tumors and to evaluate the additional information of SPECT/CT when compared to SPECT alone. Thirty (30) patients were studied: 20 were evaluated before undergoing surgery and 10 after surgery and before radiotherapy planning. The acquisition of both functional (SPECT) and morphologic (CT) images were obtained in a single session. SPECT images were firstly evaluated alone and then reinterpreted by adding the anatomical (CT) planes. Fusion imaging was successfully obtained in all patients with precise correspondence between SPECT and CT slices. SPECT/CT had a significant clinical impact in 13 (43.3%) of 30 cases; in particular, SPECT/CT accurately characterized eight lesions near sites of physiological uptake (i.e., four near ventricles/choroids plexus, three near venous sinuses, one near the skull) and localized viable tumor tissue in 5 patients evaluated after surgery. SPECT/CT with TF using this hybrid device represents a useful clinical tool in brain tumor imaging, both correctly categorizing focal areas near sites of physiological uptake and localizing viable tumor tissue after surgery.

Adult↗
PubMed2006

Spatially filtered magnetoencephalographic analysis of cortical oscillatory changes in basic brain rhythms during the Japanese 'Shiritori' Word Generation Task.

BACKGROUND: 'Shiritori' (capping verses) is a traditional Japanese word generation game, and is very familiar to native Japanese speakers. The shiritori task is expected to more strongly activate temporal language-related regions than conventional word generation to letters because of its characteristic way to make cue letters. OBJECTIVES: The aim of this study was to examine the cortical oscillatory changes in basic brain rhythms during silently performing a shiritori task. METHODS: Using synthetic aperture magnetometry (SAM) analysis of magnetoencephalography, we estimated the tomographic distributions of the statistically significant differences of the power in the alpha and beta frequency bands between the resting and the task periods. RESULTS: Significant event-related desynchronization (ERD) in the 8- to 25-Hz band, thought to reflect neural activation, was localized within task-related cortical regions with left-side dominance. The significant ERDs were estimated in both the frontal and temporal language-related regions encompassing Broca's and Wernicke's areas, although previous neuroimaging studies using word generation to letters showed neural activation predominantly in frontal regions. CONCLUSIONS: Our results show the potential of SAM analysis for reliable brain mapping of language processing, and suggest that the shiritori task might be more suitable for examining the language-related network in the brain than conventional word generation to letters.

Adult↗
PubMedDate not supplied

[The dynamics of intracortical interaction during thinking activities].

A new method is described of the brain mapping, based on determination of the probability of appearance of isofrequency components in the EEG derivations allowing to evaluate functional interaction of the brain structures in the process of psychic activity. The process of mental construction of visual image from separate elements includes three stages. At the stage of image search the focus of activity is in the occipital cortical area; in the stage of construction it moves to the frontal cortical areas; completion of the task and verbalization of the image are accompanied by joining of the cortical connections in common system. Alongside with the main focus of activity secondary focuses in the temporal cortex are also revealed during the search of the visual image. The topography of interaction at the frequencies of alpha-range in mainly determined by the stage of image construction. In case of prevalence of the image and abstract thinking shift is marked of the activity focuses at the frequencies of theta-range respectively to the right and left hemispheres.

Adolescent↗
PubMed1994

Induction of Fos immunoreactivity in the rat brain after cold-restraint induced gastric lesions and fecal excretion.

Cold-restraint alters gastrointestinal function through vagal pathways. Immunohistochemical detection of the nuclear phosphoprotein Fos (Fos-IR) was used to map brain neuronal pathways activated by cold exposure for 3 h in fasted rats maintained individually in semi-cylindrical restraining cages. Gastric lesions and fecal pellet output were also monitored. In rats exposed to cold (4 degrees C) restraint for 3 h, numerous Fos-positive nuclei were observed in the dorsal motor nucleus of the vagus, raphe pallidus, locus coeruleus, and paraventricular nucleus of the hypothalamus, and, to a lesser extent, in the raphe obscurus, parapyramidal region, and medullary noradrenergic region, bed nucleus of the stria terminalis and septum. Fecal pellet output was increased by 8 fold and gastric lesions covered 19.5 +/- 1.1% of the corpus mucosa. Rats restrained at room temperature under otherwise same conditions had little or no Fos-positive cells in these brain nuclei, no gastric erosion and a low pellet output (1.3 +/- 0.5 nb/3 h). These data, in addition to previous functional studies, provide anatomic support for the involvement of neurons in the caudal raphe nuclei, dorsal motor nucleus of the vagus and paraventricular nucleus of the hypothalamus in the autonomic and endocrine responses to cold-restraint.

Animals↗
PubMed2000

Mapping the visual recognition memory network with PET in the behaving baboon.

By means of a novel 18F-fluoro-deoxyglucose PET method designed for cognitive activation imaging in the baboon, the large-scale neural network involved in visual recognition memory in the nonhuman primate was mapped for the first time. In this method, the tracer is injected in the awake, unanesthetized, and unrestrained baboon performing the memory task, and brain imaging is performed later under light anesthesia. Brain maps obtained during a computerized trialunique delayed matching-to-sample task (lists of meaningless geometrical patterns and delay > 9 seconds) were statistically compared pixel-by-pixel to maps obtained during a specially designed visuomotor control task. When displayed onto the baboon's own anatomic magnetic resonance images, foci of significant activation were distributed along the ventral occipitotemporal pathway, the inferomedial temporal lobe (especially the perirhinal cortex and posterior hippocampal region), and the orbitofrontal cortex, consistent with lesion, single-unit, and autoradiographic studies in monkeys, as well as with activation studies in healthy humans. Additional activated regions included the nucleus basalis of Meynert, the globus pallidus and the putamen. The results also document an unexpected left-sided advantage, suggesting hemispheric functional specialization for recognition of figural material in nonhuman primates.

Animals↗
PubMed1997

[Topographic mapping of slow cortical response in guinea pigs].

Auditory slow cortical responses (SCR) were studied in 10 awake guinea pigs using topographic mapping techniques. Fourteen electrodes were installed through the guinea pig skull and fixed with dental cement. Auditory SCRs were recorded via 13 leads and brain maps were realized on a concerto system. The results showed that SCRs were relatively stable at the temporal lobe, with a stable positivity (31.25-37.50 ms TP) followed by a negativity (62.50-72.50 ms TN). Variability was seen at other leads. The foci of maximum positivity and negativity were seen at the temporal cortex. The results suggest that there are multiple contributions to SCRs which partially overlap in time, and that auditory cortex contribute significantly more than other sources. SCRs also received auditory information in parallel from the brainstem. The focus of AM-evoked SCRs was seen located at temporal lobe while that of FM-evoked SCRs at temporal and frontal lobes. It suggests that intensity analysis is essentially completed at the temporal cortex whereas precise frequency discrimination relies on function of higher integrating centers.

Animals↗
PubMed1993

Case studies in binaural interference: converging evidence from behavioral and electrophysiologic measures.

We present four case reports of elderly hearing-impaired persons demonstrating a binaural interference effect. Performance measures were poorer when stimulation was binaural than when it was monaural. In the first case the effect is shown for aided speech recognition scores. In the second case it is shown in topographic brain maps of the middle-latency auditory evoked potential. In the third and fourth cases it is shown for both aided speech recognition and the middle-latency response. The effect may be analogous to the phenomenon of binocular rivalry in the visual domain.

Acoustic Stimulation↗
PubMed2006

A novel quantitative cross-validation of different cortical surface reconstruction algorithms using MRI phantom.

Cortical surface reconstruction is important for functional brain mapping and morphometric analysis of the brain cortex. Several methods have been developed for the faithful reconstruction of surface models which represent the true cortical surface in both geometry and topology. However, there has been no explicit comparison study among those methods because each method has its own procedures, file formats, coordinate systems, and use of the reconstructed surface. There has also been no explicit evaluation method except visual inspection to validate the whole-cortical surface models quantitatively. In this study, we presented a novel phantom-based validation method of the cortical surface reconstruction algorithm and quantitatively cross-validated the three most prominent cortical surface reconstruction algorithms which are used in Freesurfer, BrainVISA, and CLASP, respectively. The validation included geometrical accuracy and mesh characteristics such as Euler number, fractal dimension (FD), total surface area, and local density of points. CLASP showed the best geometric/topologic accuracy and mesh characteristics such as FD and total surface area compared to Freesurfer and BrainVISA. In the validation of local density of points, Freesurfer and BrainVISA showed more even distribution of points on the cortical surface compared to CLASP.

Algorithms↗
PubMed2004

Memory impairment and auditory evoked potential gating deficit in schizophrenia.

Impaired sensory gating and memory function were reported in a study of 10 schizophrenic patients and 10 age- and sex-matched normal subjects. The P50 component of the auditory evoked potential was used as an index of gating. Explicit memory was tested with the Wechsler Memory Scale and implicit memory by artificial grammar learning. The schizophrenic patients showed deficits in both verbal paired associate and visual reproduction tasks. They demonstrated impaired implicit learning in color patterns but not letter strings. They also showed impaired P50 sensory gating. Three-dimensional brain mapping revealed a differential distribution of brain potentials in the processing of S1 and S2 at either P50 or N100 in both groups. However, the group difference was not statistically confirmed. In the controls, both implicit letter-string learning and explicit verbal paired associates were positively correlated with N100 gating, suggesting an association of the early attentive component with lexicons. In the schizophrenic patients, color-pattern implicit learning was positively correlated with P50 gating. The modality-specific impairment of implicit learning in schizophrenia may reflect a failure of adaptive filtering on the flooding input from color patterns.

Adult↗
PubMed1998

The continuous performance test revisited with neuroelectric mapping: impaired orienting in children with attention deficits.

A total of 11 children with attention deficit disorder (ADD) and nine control children performed a continuous performance test (CPT) of the A-X type with concurrent neuroelectric brain mapping to assess preparatory processing, purportedly mediated by the frontal lobes. This cued CPT task proved to be a highly specific task. The groups could be clearly differentiated both at the behavioral and electrophysiological level. ADD children detected fewer signals and made more false alarms. There were no major group differences in topographical distribution of the event-related potential microstates, but ADD children displayed reduced global field power (GFP) in an early CNV/P3 microstate to cues. This indicated that impaired orienting to cues, rather than impaired executive target processing, determines the initial processing stages in ADD. In comparison with data from the same task run in Utrecht, the same orienting deficit in clinically diagnosed ADHD children was demonstrated. Low resolution electromagnetic tomography (LORETA) estimated posterior sources underlying these orienting processes and the orienting deficit. This argued against frontal lobe involvement at this stage and suggested involvement of a posterior attention system.

Arousal↗
PubMed2000

[Exploration of visual memory by functional MRI].

PURPOSE: The aim of our study was to evidence the location of the cortical area triggered by visual memory tasks by he mean of functional magnetic resonance imaging examination (fMRI). METHODS: Twelve healthy volunteers underwent fMRI examination on a 1.5 Tesla magnet with echoplanar imaging sequence during figurative and non-figurative memory tasks. An area was considered to be activated if at least 10 contiguous voxels activation was noted. Activated areas were defined for both tasks and the brain mapping was realized according to Talairach atlas. RESULTS: For all examinations a bilateral activity was evidenced (area 17 and 18). In addition, a frontal activation was also noted in 83% of the cases for both tasks. However, frontal activation was bilateral in 9/10 cases for the figurative task and 6/10 cases for the non-figurative task. CONCLUSION: FMRI was able to evidence activation of cerebral areas during visual memory tasks in all our study cases. Frontal activation was not discriminative of figurative or non figurative memory. This might be probably explain by inappropriate non-figurative tests. FMRI should allow a better knowledge of memory mechanisms as well as an enhancement of functional cerebral mapping before surgery.

Adult↗