BRIAN (Brain image analysis): A toolkit for the analysis of multimodal brain datasets

The analysis of cognitive processes in man usually involves multiple examina­tion modalities which map different aspects of the brain. Among these proce­dures, at least one modality yielding anatomical information (i.e. MRI*) besidesone or more functional modalities (fMRI, PET, SPECT, EEG, MEG) are involved.Because these different examination methods yield complimentary informationabout the anatomical, metabolical and neurophysiological state of the brain, acombined data evaluation is highly desirable and will lead to results not achiev­able within one examination domain.Such studies are of importance in research (cognitive neuroscience) and ­ withan emphasis on pathological processes ­ in clinical disciplines like neurology,neurosurgery and psychiatry.We have developed a program package for the handling of image datasets(MRI, PET, SPECT, CCT) and signal datasets (EEG, MEG) which allows a com­bined analysis of these data sources in a four­dimensional coordinate space (x, y,z, and time)

Gender and age effects in structural brain asymmetry as measured by MRI texture analysis

Effects of gender and age on structural brain asymmetry were studied by 3D texture analysis in 380 adults. Asymmetry is detected by comparing the complex 3D gray-scale image patterns in the left and right cerebral hemispheres as revealed by anatomical T1-weighted MRI datasets. The Talairach and Tournoux parcellation system was applied to study the asymmetry on five levels: the whole cerebrum, nine coronal sections, 12 axial sections, boxes resulting from both coronal and axial subdivisions, and by a sliding spherical window of 9 mm diameter. The analysis revealed that the brain asymmetry increases in the anterior-posterior direction starting from the central region onward. Male brains were found to be more asymmetric than female. This gender-related effect is noticeable in all brain areas but is most significant in the superior temporal gyrus, Heschl's gyrus, the adjacent white matter regions in the temporal stem and the knee of the optic radiation, the thalamus, and the posterior cingulate. The brain asymmetry increases significantly with age in the inferior frontal gyrus, anterior insula, anterior cingulate, parahippocampal gyrus, retrosplenial cortex, coronal radiata, and knee region of the internal capsule. Asymmetry decreases with age in the optic radiation, precentral gyrus, and angular gyrus. The texture-based method reported here is based on extended multisort cooccurrence matrices that employ intensity, gradient, and anisotropy features in a uniform way. It is sensitive, simple to reproduce, robust, and unbiased in the sense that segmentation of brain compartments and spatial transformations are not necessary. Thus, it should be considered as another tool for digital morphometry in neuroscience

Estimating the effective degrees of freedom in univariate multiple regression analysis

The general linear model provides the most widely applied statistical framework for analyzing functional MRI (fMRI) data. With the increasing temporal resolution of recent scanning protocols, and more elaborate data preprocessing schemes, data independency is no longer a valid assumption. In this paper, we revise the statistical background of the general linear model in the presence of temporal autocorrelations. First, when detecting the activation signal, we explicitly account for the temporal autocorrelation structure, which yields a generalized F-test and the associated corrected (or effective) degrees of freedom (DOF). The proposed approach is data driven and thus independent of any specific preprocessing method. Then, for event-related protocols, we propose a new model for the temporal autocorrelations (“damped oscillator” model) and compare this model to another, previously used in the field (first-order autoregressive model, or AR(1) model). In the case of long fMRI time series, an efficient approximation for the number of effective DOF is provided for both models. Finally, the validity of our approach is assessed using simulated and real fMRI data and is compared with more conventional methods

Do quiescent arachnoid cysts alter CNS functional organization? An fMRI and morphometric study

OBJECTIVE: To investigate whether congenital and clinically quiescent arachnoid cysts (AC) in the left temporal fossa alter the functional organization of adjacent cortices. METHODS: fMRI mapping was applied in five right-handed asymptomatic patients to determine the functional organization of language. Moreover, morphometry was performed in each patient to gain the size of cortical surface areas and cortical thickness values in the neighboring brain adjacent to the AC and explicitly in the left opercular region. RESULTS: Four patients showed a clear left hemisphere language dominance regardless of the cyst size; a mixed laterality of language organization was found in the remaining patient. An interesting dissociation of morphometric data was assessed when comparing strongly language-related cortices in the inferior frontal gyrus with the entire neighboring cortices. Morphometry in the neighboring brain regions of the AC showed 1) overall reduced cortical surface areas and 2) a decrease in cortical thickness compared to the homologous right side. However, the surface area of the fronto-opercular region in the left inferior frontal gyrus-i.e., the pars triangularis and the pars opercularis-was larger on the left as compared to the right side. Both structures have earlier been identified to represent the morphologic substrate of language dominance in the left hemisphere. CONCLUSION: Arachnoid cysts do not disturb the normal asymmetry of hemisphere language organization despite delicate locations adjacent to the left inferior frontal gyrus

Near-infrared spectroscopy can detect brain activity during a color-word matching Stroop task in an event-related design

Brai nactivit ycanbemonitore dnon-invasivel ybynear-infrare dspectroscop y(NIRS) ,whic hhas severa ladvantage sincompariso nwit hothe rimagin gmethods ,suc hasflexibility ,portability ,low cost an dbiochemica lspecificity .Moreover ,patient san dchildre ncanberepetitivel yexamined .Therefore ,the objectiv eofthestud ywa stotes tthefeasibilit yofNIR Sfortheevent-relate dapproac hinfunctiona lbrain activatio nstudie swit hcognitiv eparadigms .Thus ,change sintheconcentratio nofoxy- ,deoxy- ,an dtotal hemoglobi nwer emeasure d byNIR Sin14health ysubject swhil eperformin ga color–wor d matching Stroo p tas k in an event-relate d design .Th ehemodynami crespons e(increas ein theconcentratio n of oxy-/tota lhemoglobi n an d decreas ein theconcentratio n ofdeoxy-hemoglobin )wa sstronge rduring incongruen tcompare dtocongruen tan dneutra ltrial softheStroo ptas kinthelatera lprefronta lcortex bilaterally .Thi sstronge rhemodynami crespons ewa sinterprete dasa stronge rbrai nactivatio nduring incongruen ttrial softheStroo ptask ,du etointerference .A ne w metho dforNIR Sdat aevaluatio nthat enable stheanalysi softhehemodynami crespons etoeac hsingl etria lisintroduced .Eac hhemodynamic respons ewa scharacterize dbytheparameter sgain ,lagan ddispersio nofa Gaussia nfunctio nfitte dby nonlinea rregression .Specifi cdifference sbetwee ntheincongruen tan dneutra lconditio nwer efoun dfor gai nan dlag .Further ,thes eparameter swer ecorrelate dwit hthebehaviora lperformance .Inconclusion, brai nactivit yma ybestudie d byNIR Susin gcognitiv estimul iinanevent-relate d design

Analyzing the neocortical fine-structure

Cytoarchitectonic fields of the human neocortex are defined by characteristic variations in the composition of a general six-layer structure. It is commonly accepted that these fields correspond to functionally homogeneous entities. Diligent techniques were developed to characterize cytoarchitectonic fields by staining sections of post-mortem brains and subsequent statistical evaluation. Fields were found to show a considerable interindividual variability in extent and relation to macroscopic anatomical landmarks. With upcoming new high-resolution magnetic resonance imaging (MRI) protocols, it appears worthwhile to examine the feasibility of characterizing the neocortical fine-structure from anatomical MRI scans, thus, defining neocortical fields by in vivo techniques. A fixated brain hemisphere was scanned at a resolution of approximately 0.3 mm. After correcting for intensity inhomogeneities in the dataset, the cortex boundaries (the white/grey matter and grey matter/background interfaces) were determined as a triangular mesh. Radial intensity profiles following the shortest path through the cortex were computed and characterized by a sparse set of features. A statistical similarity measure between features of different regions was defined, and served to define the extent of Brodmann’s Areas 4, 17, 44 and 45 in this dataset

Detection of fixed points in spatiotemporal signals by clustering method

We present a method to determine fixed points in spatiotemporal signals. A 144-dimensioanl simulated signal, similar to a Kueppers-Lortz instability, is analyzed and its fixed points are reconstructed.Comment: 3 pages, 3 figure

Quantitative mapping of the per-axon diffusion coefficients in brain white matter.

This article presents a simple method for estimating the effective diffusion coefficients parallel and perpendicular to the axons unconfounded by the intravoxel fiber orientation distribution. We also call these parameters the per-axon or microscopic diffusion coefficients