Techniques for measuring sulcal/gyral patterns in the brain as visualized through magnetic resonance scanning: BRAINPLOT and BRAINMAP

Robust estimation of sulcal morphology

While it is well established that cortical morphology differs in relation to a variety of inter-individual factors, it is often characterized using estimates of volume, thickness, surface area, or gyrification. Here we developed a computational approach for estimating sulcal width and depth that relies on cortical surface reconstructions output by FreeSurfer. While other approaches for estimating sulcal morphology exist, studies often require the use of multiple brain morphology programs that have been shown to differ in their approaches to localize sulcal landmarks, yielding morphological estimates based on inconsistent boundaries. To demonstrate the approach, sulcal morphology was estimated in three large sample of adults across the lifespan, in relation to aging. A fourth sample is additionally used to estimate test–retest reliability of the approach. This toolbox is now made freely available as supplemental to this paper: https://cmadan.github.io/calcSulc/.

Morphometric analysis of brain shape in children with nonsyndromic cleft lip and/or palate

The purpose of this study was to test for differences in brain shape among children with cleft palate only (n = 22), children with cleft lip and palate (n = 35), and controls (n = 39) using Euclidean distance matrix analysis. Sixteen percent of interlandmark distances differed between children with cleft palate only and controls, 10% differed between children with cleft lip and palate and controls, and 10% differed between children with cleft palate only and children with cleft lip and palate. Major differences in brain shape associated with cleft lip and/or palate included posterior expansion of the occipital lobe, reorientation of the cerebellum, heightened callosal midbody, and posterior displacement of the caudate nucleus and thalamus. Differences in brain shape unique to cleft palate only and to cleft lip and palate were also identified. These results expand upon previous volumetric studies on brain morphology in individuals with cleft lip and/or palate and provide additional evidence that the primary defect in cleft lip and/or palate results in both facial and brain dysmorphology.

Landmarking the brain for geometric morphometric analysis: an error study

Neuroanatomic phenotypes are often assessed using volumetric analysis. Although powerful and versatile, this approach is limited in that it is unable to quantify changes in shape, to describe how regions are interrelated, or to determine whether changes in size are global or local. Statistical shape analysis using coordinate data from biologically relevant landmarks is the preferred method for testing these aspects of phenotype. To date, approximately fifty landmarks have been used to study brain shape. Of the studies that have used landmark-based statistical shape analysis of the brain, most have not published protocols for landmark identification or the results of reliability studies on these landmarks. The primary aims of this study were two-fold: (1) to collaboratively develop detailed data collection protocols for a set of brain landmarks, and (2) to complete an intra- and inter-observer validation study of the set of landmarks. Detailed protocols were developed for 29 cortical and subcortical landmarks using a sample of 10 boys aged 12 years old. Average intra-observer error for the final set of landmarks was 1.9 mm with a range of 0.72 mm-5.6 mm. Average inter-observer error was 1.1 mm with a range of 0.40 mm-3.4 mm. This study successfully establishes landmark protocols with a minimal level of error that can be used by other researchers in the assessment of neuroanatomic phenotypes.

Cortical enlargement in autism is associated with a functional VNTR in the monoamine oxidase A gene

Monoamine oxidase A (MAOA) is an enzyme expressed in the brain that metabolizes dopamine, norepinephrine, epinephrine, and serotonin. Abnormalities of serotonin neurotransmission have long been implicated in the psychopathology of autism. A polymorphism exists within the promoter region of the MAOA gene that influences MAOA expression levels so that "low activity" alleles are associated with increased neurotransmitter levels in the brain. Individuals with autism often exhibit elevated serotonin levels. Additional studies indicate that the "low activity" allele may be associated with lower IQ and more severe autistic symptoms. In this study we genotyped the MAOA promoter polymorphism in a group of 29 males (age 2-3 years) with autism and a group of 39 healthy pediatric controls for whom brain MRI data was available. We found a consistent association between the "low activity" allele and larger brain volumes for regions of the cortex in children with autism but not in controls. We did not find evidence for over-transmission of the "low activity" allele in a separate sample of 114 affected sib pair families. Nor did we find any unknown SNPs in yet another sample of 96 probands. Future studies will determine if there is a more severe clinical phenotype associated with both the "low activity" genotype and the larger brain volumes in our sample.

Hippocampal volume and mood disorders after traumatic brain injury

BACKGROUND

Recent evidence from clinical studies and animal models of traumatic brain injury (TBI) suggest that neuronal and glial loss might progress after the initial insult in selectively vulnerable regions of the brain such as the hippocampus. There is also evidence that hippocampal dysfunction plays a role in the pathogenesis of mood disorders. We examined the relationship between hippocampal damage and mood disorders after TBI and the effect of hippocampal atrophy on the outcome of TBI patients.

METHODS

The study group consisted of 37 patients with closed head injury who were evaluated at baseline and at 3, 6, and 12 months after trauma. Psychiatric diagnosis was made with a structured clinical interview and DSM-IV criteria. Quantitative magnetic resonance imaging scans were obtained at 3-months follow-up.

RESULTS

Patients with moderate to severe head injury had significantly lower hippocampal volumes than patients with mild TBI. Patients who developed mood disorders had significantly lower hippocampal volumes than patients without mood disturbance. Furthermore, there was a significant interaction between mood disorders diagnosis and severity of TBI, by which patients with moderate to severe TBI who developed mood disorders had significantly smaller hippocampal volumes than patients with equivalent severe TBI who did not develop mood disturbance. Finally, reduced hippocampal volumes were associated with poor vocational outcome at 1-year follow-up.

CONCLUSIONS

Our findings are consistent with a "double-hit" mechanism by which neural and glial elements already affected by trauma are further compromised by the functional changes associated with mood disorders (e.g., the neurotoxic effects of increased levels of cortisol or excitotoxic damage resulting from overactivation of glutaminergic pathways). Finally, patients with greater hippocampal damage were less likely to return to a productive life 1 year after trauma.

Social function in boys with cleft lip and palate: relationship to ventral frontal cortex morphology

Isolated clefts of the lip and/or palate (ICLP) are developmental craniofacial abnormalities that have consistently been linked to increased social inhibition or shyness. Two explanations have been proposed: (1) psychosocial factors related to differences in facial appearance may lead to low self-concept and subsequent shyness, or (2) abnormal development of brain structures involved in social function, such as the ventral frontal cortex (VFC), may underlie the difference. To investigate these two possibilities this study was designed to evaluate measures of social function in relation to measures of self-concept and VFC morphology. Subjects included 30 boys (age 7-12) with ICLP and a comparison group of 43 boys without cleft in the same age category. Social function and self-concept were assessed using questionnaires with standardized scoring filled out by subjects and one of their parents. The cortical volume and surface area of the VFC, composed of the orbitofrontal cortex (OFC) and straight gyrus (SG), were evaluated using structural magnetic resonance imaging. The ICLP subjects had significantly impaired social function relative to the comparison group. No difference in self-concept was identified. VFC morphology revealed significant differences between groups, particularly decreased volume and surface area in the left SG of the ICLP group. Moreover, abnormal VFC measures were correlated with social dysfunction but measures of self-concept were not. These results are consistent with the possibility that aberrant VFC development may partially underlie social dysfunction in boys with ICLP.

Neuropsychological correlates of normal variation in emotional response to visual stimuli

Although the neural substrates of induced emotion have been the focus of numerous investigations, the factors related to individual variation in emotional experience have rarely been investigated in older adults. Twenty-six older normal subjects (mean age, 54) were shown color slides to elicit emotions of sadness, fear, or happiness and asked to rate the intensity of their emotional responses. Subjects who experienced negative emotion most intensely showed relative impairment on every aspect of the Wisconsin Card Sorting Test. Intense positive emotion was associated with relatively impaired performance on the Rey Complex Figure Test. The volume of frontal brain structures, however, was not associated with emotion responses. Hemisphere-specific executive dysfunction was associated with greater intensity of emotional experience in normal older subjects. The role of these differences in intensity of induced emotion and impairment in executive function in daily social and vocational activity should be investigated.

A soft-segmentation visualization scheme for magnetic resonance images

Prevalent visualization tools exploit gray value distribution in images through modified histogram equalization and matching technique, referred to as the window width/window level-based method, to improve visibility and enhance diagnostic value. The window width/window level tool is extensively used in magnetic resonance (MR) images to highlight tissue boundaries during image interpretation. However, the identification of different regions and distinct boundaries between them based on gray-level distribution and displayed intensity levels is extremely difficult because of the large dynamic range of tissue intensities inherent in MR images. We propose a soft-segmentation visualization scheme to generate pixel partitions from the histogram of MR image data using a connectionist approach and then generate selective visual depictions of pixel partitions using pseudo color based on an appropriate fuzzy membership function. By applying the display scheme in clinical examples in this study, we could demonstrate additional overlapping regions between distinct tissue types in healthy and diseased areas (in the brain) that could help improve the tissue characterization ability of MR images.

Catechol-O-methyl transferase Val158Met gene polymorphism in schizophrenia: working memory, frontal lobe MRI morphology and frontal cerebral blood flow

The catechol-O-methyl transferase (COMT) gene is considered a leading schizophrenia candidate gene. Although its role in increasing schizophrenia susceptibility has been conflicting, recent studies suggest the valine allele may contribute to poor cognitive function in schizophrenia. V(158)M COMT genotype was obtained on 159 schizophrenia patients and 84 healthy controls. The effects of COMT genotype on four measures of working memory/executive functions (Wisconsin Card Sorting, digit span backward, Trail Making and N-back tests) and on MRI frontal brain volumes were examined. Genotype distributions were not significantly different between patients and controls. There were no significant genotype or genotype-by-group effects on any working memory/executive function measures. No genotype or genotype-by-diagnosis interaction effects were found with MRI frontal lobe volumes. Randomization analyses using [(15)O]H(2)O positron emission tomography (PET) cerebral blood flow data found Val/Val patients had higher frontal lobe activation than Met/Met patients while performing the one-back task. Overall, these findings do not support a major role for COMT in increasing susceptibility for schizophrenia or in mediating frontal lobe function. Age-related changes and phenotypic heterogeneity of schizophrenia may influence the complex relationships between COMT genotype and cognition.

Absence of localized grey matter volume changes in the motor cortex following spinal cord injury

The consequences of spinal cord injury (SCI) have considerable effects on motor function, typically resulting in functional impairment. Pathological changes have been studied at the site of trauma, rostrocaudally within the cord, and in the periphery. Few studies, however, have investigated the consequences of SCI at the cortical level. Magnetic resonance imaging (MRI) was used to explore the morphological changes in the grey and white matter within the primary motor (M1) cortex of individuals with cervical SCI. The "precentral knob," a landmark of M1 cortex dedicated to hand function, was selected for regionally specific measurements of change. Thirty-one hemispheres of SCI subjects and 28 hemispheres of control subjects were compared using a manual measurement after the images were segmented into grey matter, white matter, and cerebral spinal fluid (CSF). No significant differences in grey matter area measured at the precentral knob were found with the manual approach. An automated voxel-based morphometric analysis was also performed and demonstrated no significant differences in grey or white matter volume within an M1 region of interest. These data suggest that there is no gross anatomical change within M1 following cervical SCI. Our previously reported findings of reorganization of cortical motor output maps following SCI therefore likely result from changes in functional organization rather than anatomical changes.

Cerebellar dysfunction in neuroleptic naive schizophrenia patients: clinical, cognitive, and neuroanatomic correlates of cerebellar neurologic signs

BACKGROUND

There is increasing evidence that, aside from motor coordination, the cerebellum also plays an important role in cognition and psychiatric disorders. Our previous studies support the hypothesis that cerebellar dysfunction may disrupt the cortico-cerebellar-thalamic-cortical circuit and, in turn, lead to cognitive dysmetria in schizophrenia. The goal of this study was to investigate cerebellar dysfunction in schizophrenia by examining the clinical, cognitive, and neuroanatomic correlates of cerebellar neurologic signs in schizophrenia patients.

METHODS

We compared the prevalence of cerebellar neurologic signs in 155 neuroleptic-naive schizophrenia patients against 155 age- and gender-matched healthy control subjects. Differences in clinical characteristics, standardized neuropsychologic performance, and magnetic resonance imaging brain volumes between patients with and without cerebellar signs were also examined.

RESULTS

Patients had significantly higher rates of cerebellar signs than control subjects, with coordination of gait and stance being the most common abnormalities. Patients with lifetime alcohol abuse or dependence were no more likely than those without alcoholism to have cerebellar signs. Presence of cerebellar signs in patients was associated with poorer premorbid adjustment, more severe negative symptoms, poorer cognitive performance, and smaller cerebellar tissue volumes.

CONCLUSIONS

These findings lend further support for cerebellar dysfunction in schizophrenia.

Initial magnetic resonance imaging volumetric brain measurements and outcome in schizophrenia: a prospective longitudinal study with 5-year follow-up

BACKGROUND

Several demographic and phenomenological variables have been identified as predictors of outcome in schizophrenia. Far fewer studies have examined the relationships between brain morphology assessed at illness onset and subsequent outcome, and their results have been contradictory.

METHODS

The relationships between magnetic resonance imaging (MRI) regional brain volumes at illness onset and outcome five years later were studied in 123 schizophrenia patients using regression and correlation analysis. Outcome measures included psychosocial functioning, weeks per year receiving inpatient treatment, and persistence of severe psychotic, disorganized and negative symptoms.

RESULTS

Temporal lobe tissue volume at onset was predictive of outcome. Smaller temporal lobe gray matter volume (both left and right) was associated with persistence of hallucinations during follow-up. There were no significant associations between hallucinations and temporal white matter, or between delusions and temporal white or gray matter volumes. None of the other volumetric brain measures were predictive of outcome.

CONCLUSIONS

The association between initial temporal lobe gray matter volume and subsequent persistent hallucinations may help identify individuals who are at higher risk for poor outcome and help guide their treatment planning. However, regional brain volumes assessed near illness onset, in general, do not appear to be indicative of subsequent outcome in schizophrenia.

Structural brain abnormalities in adult males with clefts of the lip and/or palate

PURPOSE

To evaluate brain morphology of adult males with nonsyndromic clefts of the lip and/or palate (NSCLP) in comparison to a matched healthy control group.

METHODS

Brain structure was measured using quantitative analysis of magnetic resonance images.

RESULTS

Subjects with NSCLP had significant abnormalities in brain morphology consisting of abnormally enlarged anterior regions of the cerebrum, and decreased volumes of the posterior cerebrum and cerebellum. Overall, the most severely affected region was the left temporal lobe. Furthermore, these structural abnormalities were directly related to cognitive dysfunction.

CONCLUSIONS

These findings highlight the important relationship and interplay between face and brain development.

In vivo studies of brain development by magnetic resonance techniques

Understanding of the morphological development of the human brain has largely come from neuropathological studies obtained postmortem. Magnetic resonance (MR) techniques have recently allowed the provision of detailed structural, metabolic, and functional information in vivo on the human brain. These techniques have been utilized in studies from premature infants to adults and have provided invaluable data on the sequence of normal human brain development. This article will focus on MR techniques including conventional structural MR imaging techniques, quantitative morphometric MR techniques, diffusion weighted MR techniques, and MR spectroscopy. In order to understand the potential applications and limitations of MR techniques, relevant physical and biological principles for each of the MR techniques are first reviewed. This is followed by a review of the understanding of the sequence of normal brain development utilizing these techniques. MRDD Research Reviews 6:59-67, 2000.

Neuroimaging in hyperkinetic children and adults: an overview

The application of brain imaging techniques to children with Attention Deficit/Hyperactivity Disorders is reviewed, stressing methodological aspects. Findings are still provisional, but suggest minor structural changes in frontal and candate areas, especially on the right side. Functional studies suggest reduced activation in these and other areas. The techniques do not yet contribute to individual diagnosis.

Novel vs. well-learned memory for faces: a positron emission tomography study

Previous work has suggested that familiarity/novelty of learned materials affects the circuitry involved in memory, primarily in the size of activations rather than the pattern of activation. Although this work has examined both recall and recognition, it has been limited to verbal material. In this study, we set out to determine if the same result applies to nonverbal memory. We used the same experimental design, but used faces as the memory task. Healthy volunteers thoroughly learned a set of 18 faces a week prior to the Positron Emission Tomography (PET) experiment (well-learned memory) and were asked to remember another set of 18 faces, to which they were exposed 1 min before the PET experiment (novel memory). During the PET session, their task was to recognize the faces learned a week before and the faces seen a minute before; the "remembered faces" were interspersed among entirely new (distractor) faces. We found that, unlike for verbal material, the retention interval and the familiarity level of the faces affected both the pattern and the size of activations. Comparing the novel and well-learned recognition tasks revealed that novel memory for faces is primarily a frontal-lobe task, while well-learned recognition memory for faces utilizes a more distributed neural circuit, including visual areas, which appear to serve as memory-storage sites.

Sexual dimorphism in the human brain: evaluation of tissue volume, tissue composition and surface anatomy using magnetic resonance imaging

Magnetic resonance imaging (MRI) was used to evaluate sex differences in brain morphology by comparing measures of brain tissue volume, brain tissue composition (proportions of gray and white matter), and measures of cortical surface anatomy. A large and well-matched sample of healthy women (n=42) and healthy men (n=42) were evaluated. There was a significant gender effect on intracranial volume, males being larger. However, this increase in size was limited to the cerebrum as there was no sex difference in the volume of the cerebellum. The gender difference in size of the cerebral volume was evenly distributed, with all four lobes equally larger in males compared to females. Gray and white matter tissue proportions were similar between the sexes globally. Regional tissue composition analysis showed sex differences within the parietal lobes with females having proportionately more gray matter on the right side. There were no differences between the sexes in cortical surface anatomy measures. Overall, against the background of similarity in morphology, there are differences between the sexes with regard to general and regional brain measures. The functional significance of these sex differences is unclear, but may represent the differential effects of gonadal hormones during brain growth and development.

A fuzzy logic approach to identifying brain structures in MRI using expert anatomic knowledge

We report a novel computer method for automatic labeling of structures in 3D MRI data sets using expert anatomical knowledge that is coded in fuzzy sets and fuzzy rules. The method first identifies major structures and then uses spatial relationships to these landmarks to recognize other structures. This labeling process simulates the iterative process that we ourselves use to locate structures in images. We demonstrate its application in three data sets, labeling brain MRI by locating the longitudinal and lateral fissures and the central sulci and then determining boundaries for the frontal lobes. Our method is adaptable to the identification of other anatomical structures.

Periventricular white matter injury in the premature infant is followed by reduced cerebral cortical gray matter volume at term

Periventricular white matter injury, that is, periventricular leukomalacia (PVL), the dominant form of brain injury in the premature infant, is the major neuropathological substrate associated with the motor and cognitive deficits observed later in such infants. The nature of the relationship of this lesion to the subsequent cognitive deficits is unclear, but such deficits raise the possibility of cerebral cortical neuronal dysfunction. Although cortical neuronal necrosis is not a prominent feature of brain injury in premature infants, the possibility of a deleterious effect of PVL on subsequent cerebral cortical development has not been investigated. An advanced quantitative volumetric three-dimensional magnetic resonance imaging technique was used to measure brain tissue volumes at term in premature infants with earlier ultrasonographic and magnetic resonance imaging evidence of PVL (mean gestational age at birth, 28.7 +/- 2.0 weeks; n = 10), in premature infants with normal imaging studies (mean gestational age at birth, 29.0 +/- 2.1 weeks; n = 10), and in control term infants (n = 14). Premature infants with PVL had a marked reduction in cerebral cortical gray matter at term compared with either premature infants without PVL or normal term infants (mean +/- SD: PVL, 157.5 +/- 41.5 ml; no PVL, 211.7 +/- 25.4 ml; normal term, 218.8 +/- 21.3 ml). As expected, a reduction in the volume of total brain myelinated white matter was also noted (mean +/- SD: PVL, 14.5 +/- 4.6 ml; no PVL, 23.1 +/- 6.9 ml; normal term, 27.6 +/- 10.3 ml). An apparent compensatory increase in total cerebrospinal fluid volume also was found (mean +/- SD: PVL, 64.5 +/- 15.2 ml; no PVL, 52.0 +/- 24.1 ml; normal term, 32.9 +/- 13.5 ml). PVL in the premature infant is shown for the first time to be followed by impaired cerebral cortical development. These findings may provide insight into the anatomical correlate for the intellectual deficits associated with PVL in the premature infant.

Cerebral blood flow and personality: a positron emission tomography study

OBJECTIVE

This study sought to describe brain regions associated with the personality dimension of introversion/extraversion.

METHOD

Measures of cerebral blood flow (CBF) were obtained from 18 healthy subjects by means of [150]H20 positron emission tomography. Correlations of regional CBF with introversion/extraversion were calculated, and a three-dimensional map of those correlations was generated.

RESULTS

Overall, introversion was associated with increased blood flow in the frontal lobes and in the anterior thalamus. Regions in the anterior cingulate gyrus, the temporal lobes, and the posterior thalamus were found to be correlated with extraversion.

CONCLUSIONS

The findings of the study lend support to the notion that introversion is associated with increased activity in frontal lobe regions. Moreover, the study suggests that individual differences in introversion and extraversion are related to differences in a fronto-striato-thalamic circuit.

Immunoelectrodes in protein detection: comparison between glassy carbon and a semimetallic Ni/P thin film as binding support. Biological applications

Though immunoelectrodes can allow direct detection of very low protein amounts (about 0.1 pmol) in vitro and in vivo, they are not yet widely used because they need quality improvement. Based on a few works devoted to the basic electrochemical phenomenon occurring when antibodies are linked onto a solid support and during antigen/antibody complex formation, we have coated two different supports with antibodies: the classical glassy carbon fiber or an epoxy plate covered with an amorphous semimetallic (nickel/phosphorus) thin film obtained by means of an electrochemical deposit. The antibody/antigen complex formation induces direct and/or indirect ionic movements and a current flow through the conductive support toward a very low-noise and high-sensitivity preamplifier stage in an I/V configuration. The proposed electrochemical treatment (hydrophilization), applied to both carbon and Ni/P electrodes, improves antibody binding and reliability of the response to antigens. The Ni/P probes present several advantages when compared to carbon fiber: better conductivity, possibility of surface quality control, and semimetallic nature, making them unbreakable. Several applications were proposed: somatostatin-14 detection with both carbon fiber and Ni/P plate electrodes, and histamine detection in simple and complex fluid media. Dose-response curves and analysis of the results lead us to conclude that the obtained currents are directly related to the quantity of antigen.

Morphometric analysis of the temporal lobe in temporal lobe epilepsy

PURPOSE

Using high-resolution magnetic resonance imaging (MRI), we examined the temporal neocortex and the underlying white matter in patients with unilateral temporal lobe epilepsy (TLE) and in control subjects.

METHODS

The images of 27 patients and 42 control subjects were registered into stereotaxic space, corrected for image intensity inhomogeneity, and automatically segmented into gray matter, white matter, and cerebrospinal fluid (CSF) over a predetermined extent of the temporal lobe. The surface between the gray matter and CSF was extracted, indices of curvature (IOC) of the surface were calculated, and a frequency histogram of the IOC was obtained.

RESULTS

There was significant bilateral reduction in the total volume of the temporal lobe and in the volume of gray matter. White matter volume was significantly reduced only in the temporal lobe ipsilateral to the seizure focus. There were significant changes in the position and amplitude of peaks in the frequency histogram of the IOC.

CONCLUSIONS

The volume of gray matter was negatively correlated with duration of epilepsy, suggesting that neocortical changes may be a consequence of seizures. Changes in the frequency histogram of the IOC suggested an additional alteration in the surface morphology of the temporal lobe in TLE, possibly related to sulcal widening.

No difference in hippocampus volume detected on magnetic resonance imaging in autistic individuals

Neuropathological and animal studies have implicated the hippocampus as having a potential role in autism. Current imaging methods are well suited to the detailed measurement of the volume of the hippocampus, which has received little attention in previous imaging studies in autism. We report the results of a magnetic resonance imaging (MRI) study of 35 autistic and 36 control subjects. Detailed (1.5 mm) MRI did not reveal differences in the volume of the hippocampus in autistic individuals.

Quantitative magnetic resonance imaging of brain development in premature and mature newborns

Definition in the living premature infant of the anatomical and temporal characteristics of development of critical brain structures is crucial for insight into the time of greatest vulnerability of such brain structures. We used three-dimensional magnetic resonance imaging (3D MRI) and image-processing algorithms to quantitate total brain volume and total volumes of cerebral gray matter (GM), unmyelinated white matter (WM), myelinated WM, and cerebrospinal fluid (CSF) in 78 premature and mature newborns (postconceptional age, 29-41 weeks). Total brain tissue volume was shown to increase linearly at a rate of 22 ml/wk. Total GM showed a linear increase in relative intracranial volume of approximately 1.4% or 15 ml in absolute volume per week. The pronounced increase in total GM reflected primarily a fourfold increase in cortical GM. Unmyelinated WM was found to be the most prominent brain tissue class in the preterm infant younger than 36 weeks of postconceptional age. Although minimal myelinated WM was present in the preterm infant at 29 weeks, between 35 and 41 weeks an abrupt fivefold increase in absolute volume of myelinated WM was documented. Extracerebral and intraventricular CSF was readily quantitated by this technique and found to change minimally. The application of 3D MRI and tissue segmentation to the study of human infant brain from 29 to 41 weeks of postconceptional age has provided new insights into cerebral cortical development and myelination and has for the first time provided means of quantitative assessment in vivo of early human brain development.

Intracranial contour extraction with active contour models

A novel image processing scheme for extracting the intracranial contours in axial magnetic resonance data sets is proposed. The scheme incorporates the method of active contour models, a recently introduced paradigm for contour extraction. Its performance is nearly ideal for T2-weighted images. Although the performances for proton-density-weighted images and T1-weighted images drop slightly, qualitatively satisfactory extraction still can be obtained for T1-weighted images. Due to high degree of automation, the scheme should help speed up some image processing applications that require the presegmentation of the intracranial cavity.

Regional brain enlargement in autism: a magnetic resonance imaging study

OBJECTIVE

To determine whether increased brain volume in autism, suggested in previous studies, is the result of general or regional brain size differences and to study the effect of gender on brain size and pattern of enlargement.

METHOD

Total brain volume and cerebral cortical lobe volumes were examined in 35 autistic and 36 comparison subjects using magnetic resonance imaging and an automated method of brain volume measurement.

RESULTS

After controlling for height and nonverbal IQ, the authors detected a significant diagnosis x gender effect (F = 7.4; p = .009) for total brain volume. A repeated-measures analysis of variance indicated that the pattern of enlargement (brain region x diagnosis) in autistic subjects differed from that in controls (F = 4.88; p = .0004). Subsequent sex-specific analysis revealed significantly increased total brain volume in autistic males but not females. Analysis of lobe sizes showed significant enlargement in autistic subjects in temporal, parietal, and occipital, but not frontal lobes.

CONCLUSIONS

These results suggest that brain size is increased in autism and that differences are not generalized but appear to be the result of a pattern of enlargement with increases in the size of specific cortical lobes.

Automatic atlas-based volume estimation of human brain regions from MR images

OBJECTIVE

MRI offers many opportunities for noninvasive in vivo measurement of structure-function relationships in the human brain. Although automated methods are now available for whole-brain measurements, an efficient and valid automatic method for volume estimation of subregions such as the frontal or temporal lobes is still needed.

MATERIALS AND METHODS

We adapted the Talairach atlas to the study of brain subregions. We supplemented the atlas with additional boxes to include the cerebellum. We assigned all the boxes to 1 of 12 regions of interest (ROIs) (frontal, parietal, temporal, and occipital lobes, cerebellum, and subcortical regions on right and left sides of the brain). Using T1-weighted MR scans collected with an SPGR sequence (slice thickness = 1.5 mm), we manually traced these ROIs and produced volume estimates. We then transformed the scans into Talairach space and compared the volumes produced by the two methods ("traced" versus "automatic"). The traced measurements were considered to be the "gold standard" against which the automatic measurements were compared.

RESULTS

The automatic method was found to produce measurements that were nearly identical to the traced method. We compared absolute measurements of volume produced by the two methods, as well as the sensitivity and specificity of the automatic method. We also compared the measurements of cerebral blood flow obtained through [15O]H2O PET studies in a sample of nine subjects. Absolute measurements of volume produced by the two methods were very similar, and the sensitivity and specificity of the automatic method were found to be high for all regions. The flow values were also found to be very similar by both methods.

CONCLUSION

The automatic atlas-based method for measuring the volume of brain subregions produces results that are similar to manual techniques. The method is rapid, efficient, unbiased, and not subject to the problems of rater drift or potentially poor interrater reliability that plague manual methods. Consequently, this method may be very useful for the study of structure-function relationships in the human brain.

Thalamic abnormalities in schizophrenia visualized through magnetic resonance image averaging

Schizophrenia is a complex illness characterized by multiple types of symptoms involving many aspects of cognition and emotion. Most efforts to identify its underlying neural substrates have focused on a strategy that relates a single symptom to a single brain region. An alternative hypothesis, that the variety of symptoms could be explained by a lesion in midline neural circuits mediating attention and information processing, is explored. Magnetic resonance images from patients and controls were transformed with a "bounding box" to produce an "average schizophrenic brain" and an "average normal brain." After image subtraction of the two averages, the areas of difference were displayed as an effect size map. Specific regional abnormalities were observed in the thalamus and adjacent white matter. An abnormality in the thalamus and related circuitry explains the diverse symptoms of schizophrenia parsimoniously because they could all result from a defect in filtering or gating sensory input, which is one of the primary functions of the thalamus in the human brain.