Major Sulci Research Articles

The superior frontal sulcus in the human brain: Morphology and probability maps.

The superior frontal sulcus (SFS) is the major sulcus on the dorsolateral frontal cortex that defines the lateral limit of the superior frontal gyrus. Caudally, it originates near the superior precentral sulcus (SPRS) and, rostrally, it terminates near the frontal pole. The advent of structural neuroimaging has demonstrated significant variability in this sulcus that is not captured by the classic sulcal maps. The present investigation examined the morphological variability of the SFS in 50 individual magnetic resonance imaging (MRI) scans of the human brain that were registered to the Montreal Neurological Institute (MNI) standard stereotaxic space. Two primary morphological patterns were identified: (i) the SFS was classified as a continuous sulcus or (ii) the SFS was a complex of sulcal segments. The SFS showed a high probability of merging with neighbouring sulci on the superior and middle frontal gyri and these patterns were documented. In addition, the morphological variability and spatial extent of the SFS were quantified using volumetric and surface spatial probability maps. The results from the current investigation provide an anatomical framework for understanding the morphology of the SFS, which is critical for the interpretation of structural and functional neuroimaging data in the dorsolateral frontal region, as well as for improving the accuracy of neurosurgical interventions.

The Major Sulci of the Cerebral Cortex Variations: A Report of 6 Cases

The human brain is divided into four lobes by four major sulci including the lateral, central, parieto-occipital, and calcarine sulci. These sulci were used as landmarks for the brain's higher functional areas and during brain surgical entrances. According to the previous reports the variants of these main sulci were founded. The current study aimed to show a case report about the variant of the main sulci for the human brain. This study was managed on the plastinated human brain samples during the dissection room training for medical students in the medical college at Najran University in Saudi Arabia. Our study showed that there are abnormalities in the direction and distributions of the main sulci of the brain cortex a rare case. Therefore, our findings can help surgeons to understand the sulci course and their subdivision areas on the cerebral cortex to do their procedures.

Morphological Development Trajectory and Structural Covariance Network of the Human Fetal Cortical Plate during the Early Second Trimester.

During the early second trimester, the cortical plate, or "the developing cortex", undergoes immensely complex and rapid development to complete its major complement of neurons. However, morphological development of the cortical plate and the precise patterning of brain structural covariance networks during this period remain unexplored. In this study, we used 7.0T high-resolution magnetic resonance images of brain specimens ranging from 14 to 22 gestational weeks to manually segment the cortical plate. Thickness, area expansion, and curvature (i.e., folding) across the cortical plate regions were computed, and correlations of thickness values among different cortical plate regions were measured to analyze fetal cortico-cortical structural covariance throughout development of the early second trimester. The cortical plate displayed significant increases in thickness and expansions in area throughout all regions but changes of curvature in only certain major sulci. The topological architecture and network properties of fetal brain covariance presented immature and inefficient organizations with low degree of integration and high degree of segregation. Altogether, our results provide novel insight on the developmental patterning of cortical plate thickness and the developmental origin of brain network architecture throughout the early second trimester.

The Heritability of Cortical Folding: Evidence from the Human Connectome Project

The mechanisms underlying cortical folding are incompletely understood. Prior studies have suggested that individual differences in sulcal depth are genetically mediated, with deeper and ontologically older sulci more heritable than others. In this study, we examine FreeSurfer-derived estimates of average convexity and mean curvature as proxy measures of cortical folding patterns using a large (N = 1096) genetically informative young adult subsample of the Human Connectome Project. Both measures were significantly heritable near major sulci and primary fissures, where approximately half of individual differences could be attributed to genetic factors. Genetic influences near higher order gyri and sulci were substantially lower and largely nonsignificant. Spatial permutation analysis found that heritability patterns were significantly anticorrelated to maps of evolutionary and neurodevelopmental expansion. We also found strong phenotypic correlations between average convexity, curvature, and several common surface metrics (cortical thickness, surface area, and cortical myelination). However, quantitative genetic models suggest that correlations between these metrics are largely driven by nongenetic factors. These findings not only further our understanding of the neurobiology of gyrification, but have pragmatic implications for the interpretation of heritability maps based on automated surface-based measurements.

Spatial convergence of distant cortical regions during folding explains why arteries do not cross the sylvian fissure.

Cortical folding places regions that are separated by a large distance along the cortical surface in close proximity. This process is not homogeneous; regions such as the insular opercula have a much higher cortical surface distance (CSD) to euclidean distance (ED) than others. Here the authors explore the hypothesis that in the folded brain the CSD, and not the ED, determines regions of common irrigation, because this measure corresponds more closely with the distance along the prefolded brain, where the subarachnoid arterial vascular network starts forming. The authors defined a convergence index that compared the ED to the CSD and applied it to the cortical surface reconstruction of an average brain. They then compared cortical convergence to the irrigation patterns of major sulci and fissures of the brain, by assessing whether these structures were crossed or not crossed by arterial vessels in 20 fixed hemispheres. The regions of highest convergence (top 1%) were clustered around the sylvian fissure, which is the only brain depression with high convergence values along its edges. Arterial crossings were commonly observed in every major sulcus of the brain, with the exception of the sylvian fissure, constituting a highly significant difference (p < 10-4). Arteries do not cross regions of high convergence. In the adult brain the CSD, rather than the ED, predicts the regional irrigation pattern. The distant origin of the frontal and temporal lobes creates a region of high cortical convergence, which explains why arteries do not cross the sylvian fissure.

The brain anatomy of an early Miocene felid from Ginn Quarry (Nebraska, USA)

The oldest felid specimen in the New World is a cranium from Ginn Quarry, Nebraska. We present a detailed description of the external brain anatomy of this specimen as inferred from its cranial endocast. Compared with modern felids, the Ginn Quarry specimen has a dorsoventrally lower cerebrum, with only three major sulci and a laterally narrower frontal lobe. The cerebellum is exposed to a large extent, and the posterior cerebellar vermis is straight rather than twisted as in modern felids. The shape of its cerebrum and the cortical sulcal pattern are similar to those of Proailurus and Hyperailurictis. The encephalization of the Ginn Quarry felid is the same as that of Hyperailurictis and slightly smaller than in Proailurus. The degree of cortical folding is intermediate between the conditions seen in Proailurus and Hyperailurictis. The Ginn Quarry felid differs from Proailurus in having a better developed frontal lobe, a shorter cerebellum and slightly longer peduncles. Based on brain anatomy, we suggest that the Ginn Quarry felid should not be dismissed as a ‘proailurine-grade’ felid. Instead, it should be either considered a primitive form of Hyperailurictis or assigned to a new genus.

Determinants of structural segregation and patterning in the human cortex

This study aimed at uncovering mechanisms that govern the spatio-temporal patterning of the human cortex and its structural variability, and drawing links between fetal brain development and variability in adult brains. A data-driven analytic approach based on structural MR images revealed the following findings: (1) The cortical surface can be subdivided into 13 independent regions (“communities”) based on macroscopic features. (2) Thirty centers of low inter-subject variability were found in major sulci on the cortical surface. Their variability showed a strong positive correlation with the known time points at which they appear in fetal development. Centers forming early induce a higher inter-subject regularity in a larger local vicinity, while those forming later result in smaller regions of higher variability. (3) The layout of sulcal and gyral patterns within a community is governed typically by two centers. Depending on the relative variability of each center, communities can be classified into structural sub-types. (4) Sub-types across ipsi-lateral communities are independent, but associated with the sub-type of the same community on the contra-lateral side. Results shown here integrate well with current knowledge about macroscopic, microscopic, and genetic determinants of brain development.

Correlating magnetoencephalography to stereo-electroencephalography in patients undergoing epilepsy surgery.

Magnetoencephalography and stereo-electroencephalography are often necessary in the course of the non-invasive and invasive presurgical evaluation of challenging patients with medically intractable focal epilepsies. In this study, we aim to examine the significance of magnetoencephalography dipole clusters and their relationship to stereo-electroencephalography findings, area of surgical resection, and seizure outcome. We also aim to define the positive and negative predictors based on magnetoencephalography dipole cluster characteristics pertaining to seizure-freedom. Included in this retrospective study were a consecutive series of 50 patients who underwent magnetoencephalography and stereo-electroencephalography at the Cleveland Clinic Epilepsy Center. Interictal magnetoencephalography localization was performed using a single equivalent current dipole model. Magnetoencephalography dipole clusters were classified based on tightness and orientation criteria. Magnetoencephalography dipole clusters, stereo-electroencephalography findings and area of resection were reconstructed and examined in the same space using the patient’s own magnetic resonance imaging scan. Seizure outcomes at 1 year post-operative were dichotomized into seizure-free or not seizure-free. We found that patients in whom the magnetoencephalography clusters were completely resected had a much higher chance of seizure-freedom compared to the partial and no resection groups ( P = 0.007). Furthermore, patients had a significantly higher chance of being seizure-free when stereo-electroencephalography completely sampled the area identified by magnetoencephalography as compared to those with incomplete or no sampling of magnetoencephalography results ( P = 0.012). Partial concordance between magnetoencephalography and interictal or ictal stereo-electroencephalography was associated with a much lower chance of seizure freedom as compared to the concordant group ( P = 0.0075). Patients with one single tight cluster on magnetoencephalography were more likely to become seizure-free compared to patients with a tight cluster plus scatter ( P = 0.0049) or patients with loose clusters ( P = 0.018). Patients whose magnetoencephalography clusters had a stable orientation perpendicular to the nearest major sulcus had a better chance of seizure-freedom as compared to other orientations ( P = 0.042). Our data demonstrate that stereo-electroencephalography exploration and subsequent resection are more likely to succeed, when guided by positive magnetoencephalography findings. As a corollary, magnetoencephalography clusters should not be ignored when planning the stereo-electroencephalography strategy. Magnetoencephalography tight cluster and stable orientation are positive predictors for a good seizure outcome after resective surgery, whereas the presence of scattered sources diminishes the probability of favourable outcomes. The concordance pattern between magnetoencephalography and stereo-electroencephalography is a strong argument in favour of incorporating localization with non-invasive tools into the process of presurgical evaluation before actual placement of electrodes. * Abbreviations : SECD : single equivalent current dipole SEEG : stereo-electroencephalography

A neuroimaging study in childhood autism

Background: Childhood autism is now widely viewed as being of developmental neurological origin. Abnormality in neuroimaging is reported in autism.Objectives: To delineate the proportion of structural magnetic resonance imaging (MRI) and electro encephalography (EEG) abnormality among the children with Autism and to assess any association of MRI and EEG changes with co morbid mental illness.Methods: It was a cross sectional descriptive study done at a child and adolescent consultation centre, Dhaka. The study was Carried out from January 2009 to December 2009. Both boys and girls were included in the study. A total of 42 children with childhood autism aged between two and 12 years partici­pated in this study. Diagnosis of autism was based on ICD-10(DCR) criteria. Results: Abnormalities were found to be 35.7% in MRI and 42.9% in EEG. EEG abnormalities were found in the form of defuse slow waves activities, generalized faster activities, epileptogenic discharge and mixed discharge. The abnormalities in MRI was found in the form of diffuse cortical atrophic changes, focal cortical atrophy in frontal and temporal cortex with widening of major sulci, prominent ventricles, periventricular degeneration and abnormal basal ganglia. EEG changes were significantly associated with increased number of co-morbid illness (mental retardation, epilepsy and others). Conclusion: A number of abnom1alities that observed in the present study indicative of relations between structural and physiological dysfunctions and childhood autism. Further exploratory and in-depth researches are certainly required in this field. Intervention of autism needs to address co morbidities for better outcome.

NEOCIVET: Towards accurate morphometry of neonatal gyrification and clinical applications in preterm newborns

Cerebral cortical folding becomes dramatically more complex in the fetal brain during the 3rd trimester of gestation; the process continues in a similar fashion in children who are born prematurely. To quantify this morphological development, it is necessary to extract the interface between gray matter and white matter, which is particularly challenging due to changing tissue contrast during brain maturation. We employed the well-established CIVET pipeline to extract this cortical surface, with point correspondence across subjects, using a surface-based spherical registration. We then developed a variant of the pipeline, called NEOCIVET, that quantified cortical folding using mean curvature and sulcal depth while addressing the well-known problems of poor and temporally-varying gray/white contrast as well as motion artifact in neonatal MRI. NEOCIVET includes: i) a tissue classification technique that analyzed multi-atlas texture patches using the nonlocal mean estimator and subsequently applied a label fusion approach based on a joint probability between templates, ii) neonatal template construction based on age-specific sub-groups, and iii) masking of non-interesting structures using label-fusion approaches. These techniques replaced modules that might be suboptimal for regional analysis of poor-contrast neonatal cortex. The proposed segmentation method showed more accurate results in subjects with various ages and with various degrees of motion compared to state-of-the-art methods. In the analysis of 158 preterm-born neonates, many with multiple scans (n=231; 26–40weeks postmenstrual age at scan), NEOCIVET identified increases in cortical folding over time in numerous cortical regions (mean curvature: +0.003/week; sulcal depth: +0.04mm/week) while folding did not change in major sulci that are known to develop early (corrected p<0.05). The proposed pipeline successfully mapped cortical structural development, supporting current models of cerebral morphogenesis, and furthermore, revealed impairment of cortical folding in extremely preterm newborns relative to relatively late preterm newborns, demonstrating its potential to provide biomarkers of prematurity-related developmental outcome.

Spatial distribution and longitudinal development of deep cortical sulcal landmarks in infants

Sulcal pits, the locally deepest points in sulci of the highly convoluted and variable cerebral cortex, are found to be spatially consistent across human adult individuals. It is suggested that sulcal pits are genetically controlled and have close relationships with functional areas. To date, the existing imaging studies of sulcal pits are mainly focused on adult brains, yet little is known about the spatial distribution and temporal development of sulcal pits in the first 2years of life, which is the most dynamic and critical period of postnatal brain development. Studying sulcal pits during this period would greatly enrich our limited understandings of the origins and developmental trajectories of sulcal pits, and would also provide important insights into many neurodevelopmental disorders associated with abnormal cortical foldings. In this paper, by using surface-based morphometry, for the first time, we systemically investigated the spatial distribution and temporal development of sulcal pits in major cortical sulci from 73 healthy infants, each with three longitudinal 3T MR scans at term birth, 1year, and 2years of age. Our results suggest that the spatially consistent distributions of sulcal pits in major sulci across individuals have already existed at term birth and this spatial distribution pattern keeps relatively stable in the first 2years of life, despite that the cerebral cortex expands dramatically and the sulcal depth increases considerably during this period. Specially, the depth of sulcal pits increases regionally heterogeneously, with more rapid growth in the high-order association cortex, including the prefrontal and temporal cortices, than the sensorimotor cortex in the first 2years of life. Meanwhile, our results also suggest that there exist hemispheric asymmetries of the spatial distributions of sulcal pits in several cortical regions, such as the central, superior temporal and postcentral sulci, consistently from birth to 2years of age, which likely has close relationships with the lateralization of brain functions of these regions. This study provides detailed insights into the spatial distribution and temporal development of deep sulcal landmarks in infants.

Mapping directionality specific volume changes using tensor based morphometry: An application to the study of gyrogenesis and lateralization of the human fetal brain

Tensor based morphometry (TBM) is a powerful approach to analyze local structural changes in brain anatomy. However, conventional scalar TBM methods do not completely capture all direction specific volume changes required to model complex changes such as those during brain growth. In this paper, we describe novel TBM descriptors for studying direction-specific changes in a subject population which can be used in conjunction with scalar TBM to analyze local patterns in directionality of volume change during brain development. We also extend the methodology to provide a new approach to mapping directional asymmetry in deformation tensors associated with the emergence of structural asymmetry in the developing brain. We illustrate the use of these methods by studying developmental patterns in the human fetal brain, in vivo. Results show that fetal brain development exhibits a distinct spatial pattern of anisotropic growth. The most significant changes in the directionality of growth occur in the cortical plate at major sulci. Our analysis also detected directional growth asymmetry in the peri-Sylvian region and the medial frontal lobe of the fetal brain.

Automated Extraction of the Cortical Sulci Based on a Supervised Learning Approach

It is important to detect and extract the major cortical sulci from brain images, but manually annotating these sulci is a time-consuming task and requires the labeler to follow complex protocols. This paper proposes a learning-based algorithm for automated extraction of the major cortical sulci from magnetic resonance imaging (MRI) volumes and cortical surfaces. Unlike alternative methods for detecting the major cortical sulci, which use a small number of predefined rules based on properties of the cortical surface such as the mean curvature, our approach learns a discriminative model using the probabilistic boosting tree algorithm (PBT). PBT is a supervised learning approach which selects and combines hundreds of features at different scales, such as curvatures, gradients and shape index. Our method can be applied to either MRI volumes or cortical surfaces. It first outputs a probability map which indicates how likely each voxel lies on a major sulcal curve. Next, it applies dynamic programming to extract the best curve based on the probability map and a shape prior. The algorithm has almost no parameters to tune for extracting different major sulci. It is very fast (it runs in under 1 min per sulcus including the time to compute the discriminative models) due to efficient implementation of the features (e.g., using the integral volume to rapidly compute the responses of 3-D Haar filters). Because the algorithm can be applied to MRI volumes directly, there is no need to perform preprocessing such as tissue segmentation or mapping to a canonical space. The learning aspect of our approach makes the system very flexible and general. For illustration, we use volumes of the right hemisphere with several major cortical sulci manually labeled. The algorithm is tested on two groups of data, including some brains from patients with Williams Syndrome, and the results are very encouraging.

Spike orientation may predict epileptogenic side across cerebral sulci containing the estimated equivalent dipole

Objective To evaluate whether the orientation of interictal spikes, localized in major sulci by magnetoencephalography (MEG), predicts the epileptogenic side of the sulcal wall. Methods Sixteen epilepsy patients were analyzed in whom equivalent current dipoles (ECDs) of MEG spikes were localized on the central (four patients), interhemispheric (4), or sylvian fissure (8); and the epileptogenic side across the sulci had been confirmed by seizure semiology, structural lesions, or intracranial electroencephalography (EEG). ECD was classified as epileptogenic side or normal side oriented and correlated to the scalp EEG map. Results All central ( n=50) and interhemispheric ( n=83) spike ECDs were oriented toward the epileptogenic side at peak latency. In scalp EEG, 91% of the spikes showed radial pattern of broad negativity above the sulcus whereas 9% showed tangential pattern with positive maximum above the epileptogenic side. Sylvian spikes were only found in patients with temporal lobe epilepsy (TLE). In sylvian spikes ( n=220), 73% of ECDs were oriented toward the epileptogenic side, whereas 27% were oriented toward the normal side. Conclusions In central and interhemispheric spikes, epileptogenic side cortex may be gross surface negative through the sulcal wall to the adjacent gyrus. Inconsistent orientation of the sylvian spikes suggests a complex pattern of spike propagation in TLE. Significance ECD orientation of central and interhemispheric spikes in MEG may predict the epileptogenic side.

Age related preservation and loss in optimized brain SPECT

Recent single photon emission computed tomography (SPECT) studies have reported age related increases in regional brain perfusion (called preservation here) as well as losses. To apply optimized SPECT processing to better define and understand both age related preservation and loss in brain SPECT. Brain SPECT was performed on 85 healthy subjects using Tc hexamethylpropylene amine oxime (HMPAO), processed using findings from recent optimization work, and subjected to voxel based statistical analysis. SPECT preservation was seen in white matter. This distribution differs from other SPECT reports, but is similar to that for preservation observed with structural magnetic resonance imaging (MRI). This suggests that SPECT preservation may arise from age related changes in brain anatomy, not regional cerebral blood flow (rCBF), and we demonstrate that it can arise from the partial-volume effect in areas where white matter contracts with age. Age related losses extended over the whole pre-frontal midline area and an extended pattern of focal losses was seen in the peripheral cortex that was consistent with major sulci. There were also focal losses in the cerebellum. The most significant SPECT loss was in the anterior cingulate, although no structural changes were observed there in the MRI study. A model of sulcal widening at the junction of the inter-hemispheric fissure and cingulate sulcus, when degraded by the partial-volume effect, could explain this anterior cingulate loss. Optimized processing has revealed spatial patterns for age related preservation and losses in brain SPECT that indicate their origin is primarily structural. Correction for structural effects in optimized SPECT is needed to confirm whether any regional ageing effects derive from changes in rCBF.

Spatial resolution of fMRI in the human parasylvian cortex: Comparison of somatosensory and auditory activation

In spite of its outstanding spatial resolution, the biological resolution of functional MRI may be worse because it depends on the vascular architecture of the brain. Here, we compared the activation patterns of the secondary somatosensory and parietal ventral cortex (SII/PV) with that of the primary auditory cortex and adjacent areas (AI/AII). These two brain regions are located immediately adjacent to each other on opposite banks of the Sylvian fissure, and are anatomically and functionally distinct. In 12 healthy subjects, SII/PV was activated by pneumatic tactile stimuli applied to the index finger (0.5 cm 2 contact area, 4 bar pressure), and AI/AII by amplitude-modulated tones (800 Hz carrier frequency, modulated at 24–36 Hz). Functional images were obtained with a 1.5-T scanner and were evaluated using SPM99. Sensitivity of fMRI activation in this unselected sample was 71% for tactile and 83% for auditory stimulation. Group analysis showed activation of SII/PV by tactile and activation of three locations in AI/AII by auditory stimuli. Distributions extended to the opposite side of the fissure (19–58% after tactile and 13–14% after auditory stimulation, depending on the side of stimulation/hemisphere). Morphometry of individual sulcal anatomy revealed that the course of the Sylvian fissure varied by 5.3 mm (SD) in vertical direction. Taking this into account, SII/PV was located 5.8 ± 2.7 mm above the Sylvian fissure, whereas AI/AII was located 6.3 ± 1.7 mm below the Sylvian fissure. Even in individual analysis, the most significant voxel after tactile stimuli in one subject was found on the “wrong” side of the fissure; this error could be ascribed to the spatial normalization procedure. These data show that fMRI signals may overlap substantially, even if the activated regions are separated by 12 mm across a major sulcus. Spatial normalization to an atlas template can introduce additional variance. Individual sulcal anatomy should be preferred over mean atlas locations.

Evaluation of octree regional spatial normalization method for regional anatomical matching

The goal of regional spatial normalization is to remove anatomical differences between individual three-dimensional (3D) brain images by warping them to match features of a standard brain atlas. Processing to fit features at the limiting resolution of a 3D MR image volume is computationally intensive, limiting the broad use of full-resolution regional spatial normalization. In Kochunov et al. (1999: Neuro-Image 10:724-737), we proposed a regional spatial normalization algorithm called octree spatial normalization (OSN) that reduces processing time to minutes while targeting the accuracy of previous methods. In the current study, modifications of the OSN algorithm for use in human brain images are described and tested. An automated brain tissue segmentation procedure was adopted to create anatomical templates to drive feature matching in white matter, gray matter, and cerebral-spinal fluid. Three similarity measurement functions (fast-cross correlation (CC), sum-square error, and centroid) were evaluated in a group of six subjects. A combination of fast-CC and centroid was found to provide the best feature matching and speed. Multiple iterations and multiple applications of the OSN algorithm were evaluated to improve fit quality. Two applications of the OSN algorithm with two iterations per application were found to significantly reduce volumetric mismatch (up to six times for lateral ventricle) while keeping processing time under 30 min. The refined version of OSN was tested with anatomical landmarks from several major sulci in a group of nine subjects. Anatomical variability was appreciably reduced for every sulcus investigated, and mean sulcal tracings accurately followed sulcal tracings in the target brain.

Cortical variability and asymmetry in normal aging and Alzheimer's disease.

The onset of Alzheimer's disease (AD) is accompanied by a complex and distributed pattern of neuroanatomic change, difficult to distinguish clinically from dynamic alterations in normal aging. Extreme variations in the sulcal patterns of the human cortex have made it difficult to identify diffuse and focal variations in cortical structure in neurodegenerative disease. We report the first comprehensive 3D statistical analysis of deep sulcal structure in vivo, in both normal aging and dementia. High-resolution 3D T1-weighted fast SPGR (spoiled GRASS) MRI volumes were acquired from 10 patients diagnosed with AD (NINCDS-ARDRA criteria; age: 71.9 +/- 10.7 years) and 10 normal subjects matched for age (72.9 +/- 5.6 years), gender, educational level and handedness. Scans were digitally transformed into Talairach stereotaxic space. To determine specific patterns of cortical variation in dementia patients, 3D average and probabilistic maps of primary deep sulci were developed for both normal and AD groups. Major sulci (including supracallosal, cingulate, marginal, parieto-occipital, anterior and posterior calcarine sulci, and Sylvian fissures) were modeled as complex systems of 3D surfaces using a multi-resolution parametric mesh approach. Variations and asymmetries in their extents, curvature, area and surface complexity were evaluated. Three-dimensional maps of anatomic variability, structural asymmetry and local atrophy indicated severe regionally selective fiber loss in AD. A midsagittal area loss of 24.5% at the corpus callosum's posterior midbody (P < 0.025) matched increases in structural variability in corresponding temporo-parietal projection areas. Confidence limits on 3D cortical variation, visualized in 3D, exhibited severe increases in AD from 2 to 4 mm at the callosum to a peak SD of 19.6 mm at the posterior left Sylvian fissure. Normal Sylvian fissure asymmetries (right higher than left; P < 0.0005), mapped for the first time in three dimensions, were accentuated in AD (P < 0.0002), and were greater in AD than in controls (P < 0.05). Severe AD-related increases in 3D variability and asymmetry may reflect disease-related disruption of the commissural system connecting bilateral temporal and parietal cortical zones, regions known to be at risk of early metabolic dysfunction, perfusion deficits and selective neuronal loss in AD.

Aspects of the anatomy of the cerebellum on computed tomography.

The salient features of the normal CT anatomy of the various lobules of the cerebellar hemispheres and vermis are described. The subdivisions of the vermis were found to be most constant. The surface appearance of the hemisphere lobules was also relatively constant; however, at CT these fissures are imaged at depth and this constancy is not reflected in CT images because folia cross the depths of the major sulci from one lobule to the other in a highly variable manner. The flocculus has been confused with the anterior angle of the cerebellum, and the cerebellar tonsils with the biventral lobule.

A new system for gray-level surface distribution maps of electrical activity

This report describes an integrated anatomical, electrophysiological and data management system for presenting cortical surface distribution maps. Approximately equal area projections (lateral and top) were constructed from a cross-sectional whole head atlas. Anatomical landmarks (major sulcus and gyrus locations) were also located on the outline. The outline and weights for interpolation are stored in the computer, with software for map generation directly from multilead EEG or evoked potential data. Electrode position and number can be easily varied and mapped onto any shaped space using the same program. Data derived from other sources such as xenon blood flow, brain scans or positron emission tomography can similarly be presented. The program uses a laboratory computer and emphasizes simplicity of data management and a mapping algorithm which is applicable to many forms of data.