A voxel-based morphometric study of ageing in 465 normal adult human brains

Age-differential patterns of brain activation during perception of angry faces

Functional magnetic resonance imaging (fMRI) was used to study age-related differences in the neural circuitry involved in perception of negative facial affect. During scanning, 24 younger and 22 older adults viewed blocks of angry and neutral faces. The fMRI data analysis of the angry versus neutral faces contrast demonstrated greater activation in younger versus older individuals in the right amygdala/hippocampus region, whereas older adults demonstrated greater activation in the right anterior-ventral insula cortex. Hence, normal aging seems to affect specific nodes in the neural network involved in processing negative emotional face information. This age-related change from more subcortical to more cortical involvement could reflect functional compensation within the neural system involved in perception of facial affect, or the fact that older adults process emotional information in a different manner than do young adults.

Grey matter deficits and symptom profile in first episode schizophrenia

Several studies have investigated grey matter reductions in first episode schizophrenia (FES), but few have examined the relationship between grey matter reduction and clinical profile. A group of 31 patients with strictly defined FES and 30 healthy controls underwent T1-weighted magnetic resonance imaging (MRI) scan. Voxel-based morphometry in SPM99 was used to identify four distinct regions of grey matter reduction in the FES subjects. The regions of interest (ROIs) were in the left ventral prefrontal cortex (ROI 1), left parietal and temporal cortices (ROI 2), right cerebellum (ROI 3), and right frontal and parietal cortices (ROI 4). These regions of reduction were transformed into binary masks, which were convolved with patients' pre-processed grey matter images. Patients' grey matter volumes in these regions were correlated with their composite scores on the following three symptom dimensions: Psychomotor Poverty, Disorganization and Reality Distortion. The volumes of ROIs 1, 2 and 4 were found to be significantly correlated with the Reality Distortion syndrome score. Our findings indicate that distinct, widespread grey matter reductions are present very early in the course of schizophrenia. The results also suggest a possible structural underpinning for the abnormal brain activity typically associated with symptoms of Reality Distortion.

Hippocampal atrophy in temporal lobe epilepsy is correlated with limbic systems atrophy

Hippocampal sclerosis in temporal lobe epilepsy (TLE) is often associated with hippocampal atrophy. This study assessed whether such atrophy is correlated with loss of gray matter volume in other brain regions. In 16 patients with TLE and clear magnetic resonance imaging-based evidence of hippocampal sclerosis, hippocampal volumes were determined manually and the local gray matter (LGM) amount was estimated throughout the entire brain using voxel-based morphometry. Voxelwise correlations between the volume of the sclerotic hippocampus and LGM were computed. The pattern of voxels whose LGM correlated with hippocampal volume outlined remarkably well the anatomy of the extended limbic system and included the parahippocampal region, cingulate gyrus throughout its extent, basal forebrain, thalamic nuclei, medial orbitofrontal areas and the insula. These correlations emerged mainly on the side ipsilateral to the affected hippocampus but were also found contralaterally. No such correlations were found in a group of 16 healthy controls. The present data show that hippocampal volume loss in TLE is associated with a widespread limbic systems atrophy. These findings are helpful to better understand the functional deficit and reorganization often found in temporal lobe epilepsy and will also provide a basis to assess neural plasticity in the limbic system for those patients who will undergo curative temporal lobe surgery.

Beyond affect: a role for genetic variation of the serotonin transporter in neural activation during a cognitive attention task

Prior work has highlighted the role of genetic variation within the repetitive sequence in the transcriptional control region of the serotonin (5-HT) transporter gene (5-HTT, SLC6A4) in modulating amygdala and prefrontal activation to negative emotional stimuli. However, these studies have not explicitly tested the assumption that the control condition (neutral baseline) does not itself produce changes in activation as a function of 5-HTT genotype. Using a fixation baseline condition, we show that variation in 5-HTT genotype is associated with differential activation to negative, positive, and neutral stimuli in limbic, striatal, and cortical regions. We replicate earlier reports of increased amygdala activation to negative, relative to neutral, stimuli, but then show that these differences are driven by decreased activation to neutral stimuli, rather than increased activation to negative stimuli, in carriers of the 5-HTT short allele. Using high-resolution structural images and automated processes to test for brain volume and gray matter density, we further report significant differences, as a function of 5-HTT genotype, in frontal cortical regions, anterior cingulate, and cerebellum. These functional and structural differences suggest a much broader role for 5-HT transport efficiency in brain processes than previously thought. 5-HTT genotype affects neural systems controlling affective, cognitive, and motor processes.

Neuroimaging biomarkers for clinical trials of disease-modifying therapies in Alzheimer's disease

The pathophysiologic process leading to neurodegeneration in Alzheimer's disease (AD) is thought to begin long before clinical symptoms develop. Existing therapeutics for AD improve symptoms, but increasing efforts are being directed toward the development of therapies to impede the pathologic progression of the disease. Although these medications must ultimately demonstrate efficacy in slowing clinical decline, there is a critical need for biomarkers that will indicate whether a candidate disease-modifying therapeutic agent is actually altering the underlying degenerative process. A number of in vivo neuroimaging techniques, which can reliably and noninvasively assess aspects of neuroanatomy, chemistry, physiology, and pathology, hold promise as biomarkers. These neuroimaging measures appear to relate closely to neuropathological and clinical data, such as rate of cognitive decline and risk of future decline. As this work has matured, it has become clear that neuroimaging measures may serve a variety of potential roles in clinical trials of candidate neurotherapeutic agents for AD, depending in part on the question of interest and phase of drug development. In this article, we review data related to the range of neuroimaging biomarkers of Alzheimer's disease and consider potential applications of these techniques to clinical trials, particularly with respect to the monitoring of disease progression in trials of disease-modifying therapies.

Voxel-based analysis of MRI detects abnormal visual cortex in children and adults with amblyopia

Amblyopia, sometimes called "lazy eye," is a relatively common developmental visual disorder well characterized behaviorally; however, the neural substrates associated with amblyopia in humans remain unclear. We hypothesized that abnormalities in the cerebral cortex of subjects with amblyopia exist, possibly as a result of experience-dependent neuronal plasticity. Anatomic magnetic resonance imaging (MRI) and psychophysical vision testing was carried out on 74 subjects divided into two age ranges, 7-12 years and 18-35 years, and three diagnoses, strabismic amblyopia, anisometropic amblyopia, and normal vision. We report a behavioral impairment in contrast sensitivity for subjects with amblyopia, consistent with previous reports. When the high-resolution MRI brain images were analyzed quantitatively with optimized voxel-based morphometry, results indicated that adults and children with amblyopia have decreased gray matter volume in visual cortical regions, including the calcarine sulcus, known to contain primary visual cortex. This finding was confirmed with a separate region-of-interest analysis. For the children with amblyopia, additional gray matter reductions in parietal-occipital areas and ventral temporal cortex were detected, consistent with recent reports that amblyopia can result in spatial location and object processing deficits. These data are the first to provide possible neuroanatomic bases for the loss of binocularity and visual sensitivity in children and adults with amblyopia.

Brain volumes in healthy adults aged 40 years and over: a voxel-based morphometry study

BACKGROUND AND AIMS

Gender and age effect on brain morphology have been extensively investigated. However, the great variety in methods applied to morphology partly explain the conflicting results of linear patterns of tissue changes and lateral asymmetry in men and women. The aim of the present study was to assess the effect of age, gender and laterality on the volumes of gray matter (GM) and white matter (WM) in a large group of healthy adults by means of voxel-based morphometry. This technique, based on observer-independent algorithms, automatically segments the 3 types of tissue and computes the amount of tissue in each single voxel.

METHODS

Subjects were 229 healthy subjects of 40 years of age or older, who underwent magnetic resonance (MR) for reasons other than cognitive impairment. MR images were reoriented following the AC-PC line and, after removing the voxels below the cerebellum, were processed by Statistical Parametric Mapping (SPM99). GM and WM volumes were normalized for intracranial volume.

RESULTS

Women had more fractional GM and WM volumes than men. Age was negatively correlated with both fractional GM and WM, and a gender x age interaction effect was found for WM, men having greater WM loss with advancing age. Pairwise differences between left and right GM were negative (greater GM in right hemisphere) in men, and positive (greater GM in left hemisphere) in women (-0.56+/-4.2 vs 0.99+/-4.8; p=0.019).

CONCLUSIONS

These results support side-specific accelerated WM loss in men, and may help our better understanding of changes in regional brain structures associated with pathological aging.

Voxel-based morphometry of the thalamus in patients with refractory medial temporal lobe epilepsy

Previous research has suggested that patients with refractory medial temporal lobe epilepsy (MTLE) show gray matter atrophy both within the temporal lobes as well as in the thalamus. However, these studies have not distinguished between different nuclei within the thalamus. We examined whether thalamic atrophy correlates with the nuclei's connections to other regions in the limbic system. T1-weighted MRI scans were obtained from 49 neurologically healthy control subjects and 43 patients diagnosed with chronic refractory MTLE that was unilateral in origin (as measured by ictal EEG and hippocampal atrophy observed on MRI). Measurements of gray matter concentration (GMC) were made using automated segmentation algorithms. GMC was analyzed both voxel-by-voxel (preserving spatial precision) as well as using predefined regions of interest. Voxel-based morphometry revealed intense GMC reduction in the anterior portion relative to posterior thalami. Furthermore, thalamic atrophy was greater ipsilateral to the MTLE origin than on the contralateral side. Here we demonstrate that the thalamic atrophy is most intense in the thalamic nuclei that have strong connections with the limbic hippocampus. This finding suggests that thalamic atrophy reflects this region's anatomical and functional association with the limbic system rather than a general vulnerability to damage.

Are there pre-existing neural, cognitive, or motoric markers for musical ability?

Adult musician's brains show structural enlargements, but it is not known whether these are inborn or a consequence of long-term training. In addition, music training in childhood has been shown to have positive effects on visual-spatial and verbal outcomes. However, it is not known whether pre-existing advantages in these skills are found in children who choose to study a musical instrument nor is it known whether there are pre-existing associations between music and any of these outcome measures that could help explain the training effects. To answer these questions, we compared 5- to 7-year-olds beginning piano or string lessons (n=39) with 5- to 7-year-olds not beginning instrumental training (n=31). All children received a series of tests (visual-spatial, non-verbal reasoning, verbal, motor, and musical) and underwent magnetic resonance imaging. We found no pre-existing neural, cognitive, motor, or musical differences between groups and no correlations (after correction for multiple analyses) between music perceptual skills and any brain or visual-spatial measures. However, correlations were found between music perceptual skills and both non-verbal reasoning and phonemic awareness. Such pre-existing correlations suggest similarities in auditory and visual pattern recognition as well a sharing of the neural substrates for language and music processing, most likely due to innate abilities or implicit learning during early development. This baseline study lays the groundwork for an ongoing longitudinal study addressing the effects of intensive musical training on brain and cognitive development, and making it possible to look retroactively at the brain and cognitive development of those children who emerge showing exceptional musical talent.

Region-specific changes in prefrontal function with age: a review of PET and fMRI studies on working and episodic memory

Several neuroimaging studies of cognitive ageing have found that age-related deficits in working memory (WM) and episodic memory abilities are related to changes in prefrontal cortex (PFC) function. Reviews of these neuroimaging studies have generally concluded that with age there is a reduction in the hemispheric specialization of cognitive function in the frontal lobes that may either be due to dedifferentiation of function, deficits in function and/or functional reorganization and compensation. Moreover, previous reviews have considered the PFC as homogeneous in function and have not taken into account the possibility that region specific changes in PFC function may occur with age. In the current review we performed a qualitative meta-analytic review of all the functional magnetic resonance imaging ageing studies and positron emission tomography ageing studies of WM and episodic memory that report PFC activation, to determine if any region-specific changes occur. The results indicated that in normal ageing distinct PFC regions exhibit different patterns of functional change, suggesting that age-related changes in PFC function are not homogeneous in nature. Specifically, we hypothesize that normal ageing is related to the differentiation of cortical function in a bilateral ventral PFC and deficits in function in right dorsal and anterior PFC. As a result of these changes, functional compensation in left dorsal and anterior PFC may occur. We hope that future studies will be conducted to either confirm or counter these hypotheses.

Aging affects both perceptual and lexical/semantic components of word stem priming: An event-related fMRI study

In this event-related fMRI study, brain activity patterns were compared in extensive groups of young (N=25) and older (N=38) adults, while they were performing a word stem completion priming task. Based on behavioral findings, we tested the hypothesis that aging affects only the lexical/semantic, but not the perceptual component of word stem priming. To this end, we distinguished between priming-related activity reductions in posterior regions involved in visual processing, and regions associated with lexical/semantic retrieval processes, i.e., left lateral temporal and left prefrontal regions. Both groups revealed significant priming-related response time reductions. However, in accordance with earlier findings, a larger priming effect was found in the group of young participants. In line with previous imaging studies, the groups showed common priming-related activity reductions in the anterior cingulate, and the left inferior prefrontal cortex extending into the anterior portion of the left superior temporal gyrus, and at lower thresholds also in the right occipital lobe. However, when directly comparing the groups, greater priming-related reductions were found for the young group in the left anterior superior temporal gyrus and the right posterior occipital lobe. These findings suggest that, converse to current psychological views, aging affects both perceptual and lexical/semantic components of repetition priming.

Changes in gray matter volume in patients with bipolar disorder

BACKGROUND

Several lines of evidence suggest the presence of neurofunctional abnormalities in patients with bipolar disorder. These functional abnormalities may stem from structural pathology in these or connected brain regions. Previous studies have generally used a region of interest (ROI) approach to study morphologic changes in bipolar disorder with inconsistent findings among research groups, which may reflect differences in how ROIs are defined. Voxel based morphometry (VBM) allows a more exploratory analysis without the necessity for predefined anatomic boundaries. In this study we utilized VBM to compare gray matter volume between groups of bipolar and healthy subjects.

METHODS

Thirty-two patients with bipolar disorder and 27 healthy subjects participated in structural magnetic resonance imaging (MRI) scans. MRI images were segmented, normalized to a standard stereotactic space, and compared on a voxel-by-voxel basis using statistical parametric mapping.

RESULTS

Bipolar subjects showed increased gray matter in several regions including portions of anterior cingulate, ventral prefrontal cortex, fusiform gyrus and parts of the primary and supplementary motor cortex. Bipolar subjects showed decreased gray matter volume in superior parietal lobule.

CONCLUSIONS

These data support suggestions that neurofunctional deficits are related to structural brain abnormalities in patients with bipolar disorder. The increased gray matter observed in several regions suggests that some affected areas may demonstrate volumetric expansion, at least in some patient populations.

Measurement of basal forebrain atrophy in Alzheimer's disease using MRI

Alzheimer's disease is characterized by the degeneration and loss of cholinergic neurones in the nucleus basalis Meynert, located within the substantia innominata at the ventral surface of the basal forebrain. An in vivo measure of morphological changes in the nucleus basalis Meynert would be of high relevance to better understand the structural correlate of cholinergic dysfunction in Alzheimer's disease. In this study, we applied a newly developed automated technique of image regression analysis, implemented through code written in Matlab 5.3 (MathWorks, Natick, MA), to the analysis of proton density weighted structural MRI of the basal forebrain from 13 patients with Alzheimer's disease (mean age = 77.5 years, SD = 4.4 years, 8 women) and 12 healthy elderly subjects (mean age = 62.3 years, SD = 5.6 years, 6 women). This technique allows searching a large portion of the substantia innominata for signal changes. We used corresponding MRI and histological sections of a post mortem brain to map the locations of basal forebrain cholinergic nuclei into the MRI standard space. Additionally, we used voxel-based morphometry, implemented in SPM2 (Wellcome Department of Imaging Neuroscience, London, UK) to determine correlations between signal changes in the substantia innominata and cortical grey matter atrophy in the patients with Alzheimer's disease. When matching the locations of signal reductions in the in vivo MRI to the template of basal nuclei based on the postmortem brain, signal intensity was decreased in areas corresponding to anterior lateral and anterior medial nucleus basalis Meynert and increased in the third ventricle, the transverse fissure and the optic tract in patients with Alzheimer's disease compared with controls. The reduction of the signal intensity in an area corresponding to the anterior lateral nucleus basalis Meynert was significantly correlated with reduced grey matter concentration in the bilateral prefrontal cortex, inferior parietal lobule and cingulate gyrus. Our findings suggest that signal changes occur in patients with Alzheimer's disease in the substantia innominata which may be related to the loss or degeneration of cholinergic neurones and correspond to regional cortical grey matter atrophy. If replicated in an independent sample, our technique may be useful to detect degeneration of basal forebrain cholinergic neurones in vivo.

Voxel-based morphometry and stereology provide convergent evidence of the importance of medial prefrontal cortex for fluid intelligence in healthy adults

We investigated whether a relationship exists between frontal lobe volume and fluid intelligence as measured by both Cattell's Culture Fair test and the Wechsler Adult Intelligence Scale-Revised (WAIS-R) Performance scale, but not with crystallized intelligence as measured by the WAIS-R Verbal scale, in healthy adults, using two well-established image analysis techniques applied to high-resolution MR brain images. Firstly, using voxel-based morphometry (VBM), we investigated whether a significant relationship exists between gray matter concentration and fluid intelligence on a voxel-by-voxel basis. Secondly, we applied the Cavalieri method of modern design stereology in combination with point counting to investigate possible relationships between macroscopic volumes of relevant brain regions defined as dorsolateral, dorsomedial, orbitolateral, and orbitomedial prefrontal cortex on the basis of neuroanatomical landmarks, and fluid intelligence. We also examined the effect on these relationships of normalizing regional brain volumes to intracranial volume. VBM analysis revealed a positive correlation between gray matter concentration in the medial region of prefrontal cortex and Culture Fair scores (corrected for multiple comparisons), and also WAIS-R Performance Intelligence sum of scaled scores (SSS) (uncorrected for multiple comparisons before controlling for age, and this converges with the stereological finding of the positive correlation between volume of dorsomedial prefrontal cortex normalized to intracranial volume and Culture Fair scores after controlling for age. WAIS-R Verbal Intelligence SSS showed no correlations. We interpret our findings, from independent analyses of both VBM and stereology, as evidence of the importance of medial prefrontal cortex in supporting fluid intelligence.

Longitudinal evaluation of cerebral morphological changes in Parkinson's disease with and without dementia

OBJECTIVE

To investigate the pattern of brain atrophy across time in a sample of Parkinson's disease (PD) patients with and without dementia using voxelbased morphometry (VBM) analysis.

METHODS

The initial sample comprised thirteen non-demented PD patients and sixteen demented patients. Longitudinal cognitive assessment and structural MRI were performed. The mean follow-up period was 25 months (SD=5.2). From this initial group, eight PD patients with dementia (5 men and 3 women) and eleven PD patients without dementia (7 men and 4 women) were reevaluated. MRI 3D structural images were acquired and analyzed by means of the optimized VBM procedure with Statistical Parametric Mapping (SPM2).

RESULTS

VBM analysis showed a progressive grey matter volume decrease in patients with PD without dementia in limbic, paralimbic and neocortical associative temporooccipital regions. In patients with dementia the loss mainly involved neocortical regions.

CONCLUSION

VBM revealed a significant loss of grey matter volume in PD patients with and without dementia with disease progression. The decrease in limbic and paralimbic regions is widespread in non-demented patients. Neocortical volume reduction is the most relevant finding in patients with dementia. This suggests that the neocortex is a substrate for dementia in Parkinson disease.

Traumatic brain injury and grey matter concentration: a preliminary voxel based morphometry study

BACKGROUND

Magnetic resonance imaging (MRI) studies have shown diffuse cerebral atrophy following traumatic brain injury. In the past, quantitative volumetric analysis of these changes was carried out by manually tracing specific regions of interest. In contrast, voxel based morphometry (VBM) is a fully automated technique that allows examination of the whole brain on a voxel by voxel basis.

OBJECTIVE

To use VBM to evaluate changes in grey matter concentration following traumatic brain injury.

METHODS

Nine patients with a history of traumatic brain injury (ranging from mild to severe) about one year previously were compared with nine age and sex matched healthy volunteers. T1 weighted three dimensional MRI images were acquired and then analysed with statistical parametric mapping software (SPM2). The patients with traumatic brain injury also completed cognitive testing to determine whether regional grey matter concentration correlated with a measure of attention and initial injury severity.

RESULTS

Compared with controls, the brain injured patients had decreased grey matter concentration in multiple brain regions including frontal and temporal cortices, cingulate gyrus, subcortical grey matter, and the cerebellum. Decreased grey matter concentration correlated with lower scores on tests of attention and lower Glasgow coma scale scores.

CONCLUSIONS

Using VBM, regions of decreased grey matter concentration were observed in subjects with traumatic brain injury compared with well matched controls. In the brain injured patients, there was a relation between grey matter concentration and attentional ability.

Structural brain correlates of prepulse inhibition of the acoustic startle response in healthy humans

Neural regions modulating prepulse inhibition (PPI) of the startle response, an operational measure of sensorimotor gating, are well established from animal studies using surgical and pharmacological procedures. The limbic and cortico-pallido-striato-thalamic circuitry is thought to be responsible for modulation of PPI in the rat. The involvement of this circuitry in human PPI is suggested by observations of deficient PPI in a number of neuropsychiatric disorders characterized by abnormalities at some level in this circuitry and recent functional neuroimaging studies in humans. The current study sought to investigate structural neural correlates of PPI in a sample of twenty-four right-handed, healthy subjects (10 men, 14 women). Subjects underwent magnetic resonance imaging (MRI) at 1.5 T and were assessed (off-line) on acoustic PPI using electromyographic recordings of the orbicularis oculi muscle beneath the right eye. Optimized volumetric voxel-based morphometry (VBM) implemented in SPM99 was used to investigate the relationship of PPI (prepulse onset-to-pulse onset interval 120 ms) to regional grey matter volumes, covarying for sex. Significant positive correlations were obtained between PPI and grey matter volume in the hippocampus extending to parahippocampal gyrus, basal ganglia including parts of putamen, globus pallidus, and nucleus accumbens, superior temporal gyrus, thalamus, and inferior frontal gyrus. These findings identify the relationship between PPI and grey matter availability on a highly spatially localized scale in brain regions shown to be activated in recent functional neuroimaging studies in association with PPI in healthy humans and demonstrate the validity of structural neuroimaging methods in delineating the neural mechanisms underlying human PPI.

Brain abnormalities underlying altered activation in dyslexia: a voxel based morphometry study

Voxel-based morphometry was used to assess the consistency among functional imaging and brain morphometry data in developmental dyslexia. Subjects, from three different cultural contexts (UK, France and Italy), were the same as those described in a previous PET activation paper, which revealed a common pattern of reduced activation during reading tasks in the left temporal and occipital lobes. We provide evidence that altered activation observed within the reading system is associated with altered density of grey and white matter of specific brain regions, such as the left middle and inferior temporal gyri and the left arcuate fasciculus. This supports the view that dyslexia is associated with both local grey matter dysfunction and with altered connectivity among phonological/reading areas. The differences were replicable across samples confirming that the neurological disorder underlying dyslexia is the same across the cultures investigated in the study.

Chronic back pain is associated with decreased prefrontal and thalamic gray matter density

The role of the brain in chronic pain conditions remains speculative. We compared brain morphology of 26 chronic back pain (CBP) patients to matched control subjects, using magnetic resonance imaging brain scan data and automated analysis techniques. CBP patients were divided into neuropathic, exhibiting pain because of sciatic nerve damage, and non-neuropathic groups. Pain-related characteristics were correlated to morphometric measures. Neocortical gray matter volume was compared after skull normalization. Patients with CBP showed 5-11% less neocortical gray matter volume than control subjects. The magnitude of this decrease is equivalent to the gray matter volume lost in 10-20 years of normal aging. The decreased volume was related to pain duration, indicating a 1.3 cm3 loss of gray matter for every year of chronic pain. Regional gray matter density in 17 CBP patients was compared with matched controls using voxel-based morphometry and nonparametric statistics. Gray matter density was reduced in bilateral dorsolateral prefrontal cortex and right thalamus and was strongly related to pain characteristics in a pattern distinct for neuropathic and non-neuropathic CBP. Our results imply that CBP is accompanied by brain atrophy and suggest that the pathophysiology of chronic pain includes thalamocortical processes.

The brain-derived neurotrophic factor val66met polymorphism and variation in human cortical morphology

A variation in the BDNF gene (val66met) affects the function of BDNF in neurons, predicts variation in human memory, and is associated with several neurological and psychiatric disorders. Here, we show that, in magnetic resonance imaging scans of a large sample of normal individuals, this polymorphism affects the anatomy of the hippocampus and prefrontal cortex, identifying a genetic mechanism of variation in brain morphology related to learning and memory.

Selective atrophy of left hemisphere and frontal lobe of the brain in old men

In this study, volumes of the whole brain, hemispheres, and frontal lobes of young and elderly adults were quantified by an automated method. Effects of age, sex, and side on absolute and relative volumes of the brain structures were evaluated. Compared with the young group, elderly participants showed a 15% volume loss in the whole brain and hemispheres, and a 22% volume loss in the frontal lobes. The relative volume of the left hemisphere in the elderly group decreased more than that of the right hemisphere. Elderly men showed significantly greater left hemisphere and left frontal lobe volume losses than did elderly women, indicating that the larger left hemisphere relative volume reduction is largely contributed to by selective atrophy of the left frontal lobe volume in elderly men. These results may reflect age- and sex-related functional deterioration in the left brain.

Neuroimaging of Bipolar Disorder: Emphasis on Novel MRI Techniques

The explosion of neuroimaging in the last decade has contributed to a revision of the concept of bipolar disorder, which was traditionally seen as a cyclic illness with return to normality between episodes lacking "by default" permanent brain abnormalities. A conspicuous corpus of neuroimaging and neuropathology studies indicates that brain changes occur in bipolar disorder, although their etiology and their relation to clinical features are yet to be established. This review summarizes the results from magnetic resonance imaging studies using conventional and novel techniques in patients with bipolar disorder.

Variation in DISC1 affects hippocampal structure and function and increases risk for schizophrenia

Disrupted-in-schizophrenia 1 (DISC1) is a promising schizophrenia candidate gene expressed predominantly within the hippocampus. We typed 12 single-nucleotide polymorphisms (SNPs) that covered the DISC1 gene. A three-SNP haplotype [hCV219779 (C)-rs821597 (G)-rs821616 (A)] spanning 83 kb of the gene was associated with schizophrenia in a family-based sample (P = 0.002). A common nonconservative SNP (Ser704Cys) (rs821616) within this haplotype was associated with schizophrenia (P = 0.004). Based on primary expression of DISC1 in hippocampus, we hypothesized that allelic variation at Ser704Cys would have a measurable impact on hippocampal structure and function as assayed via specific hippocampus-related intermediate phenotypes. In addition to overtransmission in schizophrenia, the Ser allele was associated with altered hippocampal structure and function in healthy subjects, including reduced hippocampal gray matter volume and altered engagement of the hippocampus during several cognitive tasks assayed with functional magnetic resonance imaging. These convergent data suggest that allelic variation within DISC1, either at Ser704Cys or haplotypes monitored by it, increases the risk for schizophrenia and that the mechanism of this effect involves structural and functional alterations in the hippocampal formation.

A stochastic model for studying the laminar structure of cortex from MRI

The human cerebral cortex is a laminar structure about 3 mm thick, and is easily visualized with current magnetic resonance (MR) technology. The thickness of the cortex varies locally by region, and is likely to be influenced by such factors as development, disease and aging. Thus, accurate measurements of local cortical thickness are likely to be of interest to other researchers. We develop a parametric stochastic model relating the laminar structure of local regions of the cerebral cortex to MR image data. Parameters of the model include local thickness, and statistics describing white, gray and cerebrospinal fluid (CSF) image intensity values as a function of the normal distance from the center of a voxel to a local coordinate system anchored at the gray/white matter interface. Our fundamental data object, the intensity-distance histogram (IDH), is a two-dimensional (2-D) generalization of the conventional 1-D image intensity histogram, which indexes voxels not only by their intensity value, but also by their normal distance to the gray/white interface. We model the IDH empirically as a marked Poisson process with marking process a Gaussian random field model of image intensity indexed against normal distance. In this paper, we relate the parameters of the IDH model to the local geometry of the cortex. A maximum-likelihood framework estimates the parameters of the model from the data. Here, we show estimates of these parameters for 10 volumes in the posterior cingulate, and 6 volumes in the anterior and posterior banks of the central sulcus. The accuracy of the estimates is quantified via Cramer-Rao bounds. We believe that this relatively crude model can be extended in a straightforward fashion to other biologically and theoretically interesting problems such as segmentation, surface area estimation, and estimating the thickness distribution in a variety of biologically relevant contexts.

Thalamic atrophy in Huntington's disease co-varies with cognitive performance: a morphometric MRI analysis

The pattern of motor, behavioral and cognitive symptoms in Huntington's disease (HD) implicates dysfunction of basal-ganglia-thalamo-cortical circuits. This study explored if cognitive performance in HD is correlated with localized cerebral changes. Psychomotor functions were investigated by verbal fluency, Stroop color word and Digit Symbol tests in 44 HD patients and 22 controls. Three-dimensional magnetic resonance imaging (MRI) data were analyzed with regard to regional gray matter changes by use of the observer-independent whole-brain-based approach of voxel-based morphometry (VBM). Using statistical parametric mapping, the MRI data of the HD patients were analyzed in an ANCOVA including the individual results of the neuropsychological tests. Besides striatal areas, symmetrical regional atrophy of the thalamus was found to co-vary significantly with cognitive performance (P < 0.001, corrected for multiple comparisons). In particular, thalamic subnuclei projecting to prefrontal areas (dorsomedial subnucleus) and connected to the striatum (centromedian/parafascicular and ventrolateral nuclear complex) displayed volume loss, in agreement with neuropathological studies. These results suggest that thalamic degeneration contributes in an important way to the impairment of executive function in early HD. Patients who are impaired in executive tests display structural double lesions of the basal-ganglia-thalamo-cortical circuitry both at the striatal and at the thalamic level.

Anatomical signatures of dyslexia in children: unique information from manual and voxel based morphometry brain measures

Thirteen male control and thirteen male dyslexic children (age, 121-152 months) were studied to determine if voxel based morphometry (VBM) could identify anatomical differences in the right cerebellar anterior lobe, and right and left pars triangularis that were identified with manual measures of the same children. VBM demonstrated significant gray and white matter differences in these three brain regions. In contrast to the manual results, these differences were not significant after controlling for brain volume, suggesting the manual measures captured additional important variance that distinguished the groups. Post-hoc VBM comparisons demonstrated white matter volume differences in a left temporal-parietal region that are consistent in location with results from diffusion tensor imaging studies of dyslexia. The VBM analyses also identified, gray matter volume differences in the left and right lingual gyrus, left inferior parietal lobule and cerebellum, areas that had not been examined with manual methods. We conclude that manual and automated methods provide valuable and complementary approaches to the search for functionally significant neurobiological characteristics of dyslexia.

Cerebral Structural Changes in Severe Obstructive Sleep Apnea

Obstructive sleep apnea is associated with abnormalities in neuropsychologic function, and defects in respiratory control may contribute to pathogenesis. Abnormalities may be reflected in structural brain changes. Twenty-seven male untreated patients with severe sleep apnea without comorbidities, and 24 age-matched control subjects, had T1-weighted brain imaging in a high-resolution magnetic resonance scanner. Twenty-three patients with sleep apnea had repeat imaging after 6 months of continuous positive airways pressure treatment. No areas of gray matter volume change were found in patients using an optimized voxel-based morphometry technique, at p < 0.05 adjusted for multiple comparisons (despite the method being sensitive to changes in gray matter fraction of 0.17 or less in all voxels). Furthermore, no differences were seen in bilateral hippocampal, temporal lobe, or whole brain volumes, assessed by manual tracing of anatomical borders. No longitudinal changes were seen in gray matter density or regional volumes after treatment, but whole brain volume decreased slightly. We have found no gray matter volume deficits nor focal structural changes in severe obstructive sleep apnea. Whole brain volume decreases without focal changes after 6 months of continuous positive airways pressure treatment.

5-HTTLPR polymorphism impacts human cingulate-amygdala interactions: a genetic susceptibility mechanism for depression

Carriers of the short allele of a functional 5' promoter polymorphism of the serotonin transporter gene have increased anxiety-related temperamental traits, increased amygdala reactivity and elevated risk of depression. Here, we used multimodal neuroimaging in a large sample of healthy human subjects to elucidate neural mechanisms underlying this complex genetic association. Morphometrical analyses showed reduced gray matter volume in short-allele carriers in limbic regions critical for processing of negative emotion, particularly perigenual cingulate and amygdala. Functional analysis of those regions during perceptual processing of fearful stimuli demonstrated tight coupling as a feedback circuit implicated in the extinction of negative affect. Short-allele carriers showed relative uncoupling of this circuit. Furthermore, the magnitude of coupling inversely predicted almost 30% of variation in temperamental anxiety. These genotype-related alterations in anatomy and function of an amygdala-cingulate feedback circuit critical for emotion regulation implicate a developmental, systems-level mechanism underlying normal emotional reactivity and genetic susceptibility for depression.

Voxel-based morphometry versus region of interest: a comparison of two methods for analyzing gray matter differences in schizophrenia

Many previous studies exploring cortical gray matter (GM) differences in schizophrenia have used "region of interest" (ROI) measurements to manually delineate GM volumes. Recently, some investigators have instead employed voxel-based morphometry (VBM), an automated whole-brain magnetic resonance image measurement technique. The purpose of the current study was to compare the above methods in calculating GM distributions in schizophrenia patients relative to matched controls. Using ROIs, Buchanan et al. (Buchanan, R.W., Francis, A., Arango, C., Miller, K., Lefkowitz, D.M., McMahon, R.P., Barta, P.E. and Pearlson, G.D., 2004. Morphometric assessment of the heteromodal association cortex in schizophrenia. Am J Psychiatry. 161 (2), 322-331.) found decreased dorsolateral prefrontal GM volume and altered symmetry of inferior parietal GM in schizophrenia patients. We hypothesized that VBM analyses of the same data would complement the ROI findings. As predicted, VBM analyses replicated results of less left inferior and right superior frontal cortical GM in schizophrenia. Additionally, VBM uncovered a significantly lower concentration of GM in the middle and superior temporal gyri, sought but not detected using ROIs, but did not replicate the parietal changes. The principal explanation for these differences may be the methodological differences between voxel-averaged, landmark-based ROI analyses and the single, voxel-by-voxel whole brain VBM measurements. Although VBM is rapid and fully automated, it is not a replacement for manual ROI-based analyses. Both methods provide different types of information and should thus be used in tandem.

Selective reduction in amygdala volume in pediatric anxiety disorders: a voxel-based morphometry investigation

BACKGROUND

Significant controversy has emerged concerning pediatric anxiety disorders. Some researchers question the justification for diagnosing and treating pediatric anxiety disorders, owing to concerns about the inappropriate medicalization of social problems. Others note the importance of diagnosis and treatment, given that pediatric anxiety disorders represent a strong risk factor for serious adult mental disorders. We examine the neural correlates of pediatric anxiety disorders, to consider the validity of the categorization scheme used in recent treatment studies.

METHODS

Using inclusion criteria derived from recent treatment trials, we compared gray matter volume throughout the brain in children with and without anxiety. Morphometric analyses used optimized voxel-based morphometry, an automated method for examining structural changes throughout the brain.

RESULTS

Reductions in left amygdala gray matter volume were noted for patients with anxiety disorders relative to comparison subjects.

CONCLUSIONS

We discuss implications of these findings for current controversies.

Optimized voxel-based morphometry of gray matter volume in first-episode, antipsychotic-naive schizophrenia

This study examined gray matter (GM) volume abnormalities in first-episode, antipsychotic-naïve Indian schizophrenia patients. Magnetic resonance images of 18 schizophrenia patients and 18 matched healthy comparison subjects were analyzed by optimized voxel-based morphometry. Schizophrenia patients had significantly smaller global GM and greater global CSF volumes and smaller regional GM volume in superior frontal, inferior frontal, cingulate, post-central, superior temporal and parahippocampal gyri, inferior parietal lobule, insula, caudate nuclei, thalamus and cerebellum. Findings suggest limbic, heteromodal cortical, striatal, thalamic and cerebellar abnormalities in schizophrenia.

Regional volume deviations of brain structure in schizophrenia and psychotic bipolar disorder: computational morphometry study

BACKGROUND

It is unclear whether schizophrenia and psychotic bipolar disorder are associated with similar deviations of brain morphometry.

AIMS

To assess volumetric abnormalities of grey and white matter throughout the entire brain in individuals with schizophrenia or with bipolar disorder compared with the same control group.

METHOD

Brain scans were obtained by magnetic resonance imaging from 25 people with schizophrenia, 37 with bipolar disorder who had experienced psychotic symptoms and 52 healthy volunteers. Regional deviation in grey and white matter volume was assessed using computational morphometry.

RESULTS

Individuals with schizophrenia had distributed grey matter deficit predominantly involving the fronto-temporal neocortex, medial temporal lobe, insula, thalamus and cerebellum, whereas those with bipolar disorder had no significant regions of grey matter abnormality. Both groups had anatomically overlapping white matter deficits in regions normally occupied by major longitudinal and interhemispheric tracts.

CONCLUSIONS

Schizophrenia and psychotic bipolar disorder are associated with distinct grey matter deficits but anatomically coincident white matter abnormalities.

Linking retinotopic fMRI mapping and anatomical probability maps of human occipital areas V1 and V2

Using functional MRI, we characterized field sign maps of the occipital cortex and created three-dimensional maps of these areas. By averaging the individual maps into group maps, probability maps of functionally defined V1 or V2 were determined and compared to anatomical probability maps of Brodmann areas BA17 and BA18 derived from cytoarchitectonic analysis (Amunts, K., Malikovic, A., Mohlberg, H., Schormann, T., Zilles, K., 2000. Brodmann's areas 17 and 18 brought into stereotaxic space-where and how variable? NeuroImage 11, 66-84). Comparison of areas BA17/V1 and BA18/V2 revealed good agreement of the anatomical and functional probability maps. Taking into account that our functional stimulation (due to constraints of the visual angle of stimulation achievable in the MR scanner) only identified parts of V1 and V2, for statistical evaluation of the spatial correlation of V1 and BA17, or V2 and BA18, respectively, the a priori measure kappa was calculated testing the hypothesis that a region can only be part of functionally defined V1 or V2 if it is also in anatomically defined BA17 or BA18, respectively. kappa = 1 means the hypothesis is fully true, kappa = 0 means functionally and anatomically defined visual areas are independent. When applying this measure to the probability maps, kappa was equal to 0.84 for both V1/BA17 and V2/BA18. The data thus show a good correspondence of functionally and anatomically derived segregations of early visual processing areas and serve as a basis for employing anatomical probability maps of V1 and V2 in group analyses to characterize functional activations of early visual processing areas.

Measures of brain morphology and infarction in the framingham heart study: establishing what is normal

Numerous anatomical and brain imaging studies find substantial differences in brain structure between men and women across the span of human aging. The ability to extend the results of many of these studies to the general population is limited, however, due to the generally small sample size and restrictive health criteria of these studies. Moreover, little attention has been paid to the possible impact of brain infarction on age-related differences in regional brain volumes. Given the current lack of normative data on gender and aging related differences in regional brain morphology, particularly with regard to the impact of brain infarctions, we chose to quantify brain MRIs from more than 2200 male and female participants of the Framingham Heart Study who ranged in age from 34 to 97 years. We believe that MRI analysis of the Framingham Heart Study more closely represents the general population enabling more accurate estimates of regional brain changes that occur as the consequence of normal aging. As predicted, men had significantly larger brain volumes than women, but these differences were generally not significant after correcting for gender related differences in head size. Age explained approximately 50% of total cerebral brain volume differences, but age-related differences were generally small prior to age 50, declining substantially thereafter. Frontal lobe volumes showed the greatest decline with age (approximately 12%), whereas smaller differences were found for the temporal lobes (approximately 9%). Age-related differences in occipital and parietal lobe were modest. Age-related gender differences were generally small, except for the frontal lobe where men had significantly smaller lobar brain volumes throughout the age range studied. The prevalence of MRI infarction was common after age 50, increased linearly with age and was associated with significantly larger white matter hyperintensity (WMH) volumes beyond that associated with age-related differences in these measures. Amongst men, the presence of MRI infarction was associated with significant age-related reductions in total brain volume. Finally, statistically significant associations were found between the volume of MRI infarcts in cubic centimeters and all brain measures with the exception of parietal lobe volume for individuals where the volume of MRI infarctions was measured. These data serve to define age and gender differences in brain morphology for the Framingham Heart Study. To the degree participants of the Framingham Heart Study are representative the general population, these data can serve as norms for comparison with morphological brain changes associated with aging and disease. In this regard, these cross-sectional quantitative estimates suggest that age-related tissue loss differs quantitatively and qualitatively across brain regions with only minor differences between men and women. In addition, MRI evidence of cerebrovascular disease is common to the aging process and associated with smaller regional brain volumes for a given age, particularly for men. We believe quantitative MRI studies of the Framingham community enables exploration of numerous issues ranging from understanding normal neurobiology of brain aging to assessing the impact of various health factors, particularly those related to cerebrovascular disease, that appear important to maintaining brain health for the general population.

Mapping postnatal mouse brain development with diffusion tensor microimaging

While mouse brain development has been extensively studied using histology, quantitative characterization of morphological changes is still a challenging task. This paper presents how developing brain structures can be quantitatively characterized with magnetic resonance diffusion tensor microimaging coupled with techniques of computational anatomy. High resolution diffusion tensor images of ex vivo postnatal mouse brains provide excellent contrasts to reveal the evolutions of mouse forebrain structures. Using anatomical landmarks defined on diffusion tensor images, tissue level growth patterns of mouse brains were quantified. The results demonstrate the use of these techniques to three-dimensionally and quantitatively characterize brain growth.

Clinical deficits correlate with regional cerebral atrophy in progressive supranuclear palsy

Most cerebral imaging studies of patients with progressive supranuclear palsy (PSP) have noted subtle atrophy, although the full extent of atrophy and any correlates to clinical features have not been determined. We used voxel-based morphometry analysis of grey matter, white matter and CSF on MRI brain scans to map the statistical probability of regional tissue atrophy in 21 patients with PSP, 17 patients with Parkinson's disease and 23 controls. PSP and Parkinson's disease cohorts were selected to approximate the mid-stages of their respective disease courses. Where regions of significant tissue atrophy were identified in a disease group relative to controls, the probability of tissue loss within those regions was correlated with global indices of motor disability, and behavioural and cognitive disturbance for that disease group. Minimal regional atrophy was observed in Parkinson's disease. PSP could be distinguished from both controls and Parkinson's disease by symmetrical tissue loss in the frontal cortex (maximal in the orbitofrontal and medial frontal cortices), subcortical nuclei (midbrain, caudate and thalamic) as well as periventricular white matter. For PSP, motor deficits correlated with atrophy of the caudate and motor cingulate, while behavioural changes related to atrophy in the orbitofrontal cortex and midbrain. These data suggest that intrinsic neurodegeneration of specific subcortical nuclei and frontal cortical subregions together contribute to motor and behavioural disturbances in PSP and differentiate this disorder from Parkinson's disease within 2-4 years of symptom onset.

Program for Assisted Labeling of Sulcal Regions (PALS): description and reliability

With the improvements in techniques for generating surface models from magnetic resonance (MR) images, it has recently become feasible to study the morphological characteristics of the human brain cortex in vivo. Studies of the entire surface are important for measuring global features, but analysis of specific cortical regions of interest provides a more detailed understanding of structure. We have previously developed a method for automatically segmenting regions of interest from the cortical surface using a watershed transform. Each segmented region corresponds to a cortical sulcus and is thus termed a "sulcal region." In this work, we describe two important augmentations of this methodology. First, we describe a user interface that allows for the efficient labeling of the segmented sulcal regions called the Program for Assisted Labeling of Sulcal Regions (PALS). An additional augmentation allows for even finer divisions on the cortex with a methodology that employs the fast marching technique to track a curve on the cortical surface that is then used to separate segmented regions. After regions of interest have been identified, we compute both the cortical surface area and gray matter volume. Reliability experiments are performed to assess both the long-term stability and short-term repeatability of the proposed techniques. These experiments indicate the proposed methodology gives both highly stable and repeatable results.

Structural white matter deficits in high-functioning individuals with autistic spectrum disorder: a voxel-based investigation

A number of imaging and neuropathological studies have reported structural abnormalities in white matter areas such as the corpus callosum in autism spectrum disorder (ASD). Differences in both global brain volume and the size of specific neural structures have been reported. In order to expand these previously reported findings and to describe more precisely the nature of such structural changes, we performed a voxel-based morphometric whole brain analysis, using a group-specific template, in male adolescents with ASD. Fifteen individuals with normal intelligence and ASD, and a group of 16 controls, matched for age, sex, and IQ, were investigated. High-resolution T1-weighted 3D data sets were acquired and analysed. Local white matter volume deficits were found in the corpus callosum, particularly in the anterior splenium and isthmus, and right hemisphere. White matter volume deficits were also found in the left middle temporal, right middle frontal, and left superior frontal gyri. No significant areas of increased white matter volume were found. Our findings support the hypothesis that reduced white matter volume in the corpus callosum and right hemisphere may play a role in the pathophysiology of ASD.

Age- and sex-related effects on the neuroanatomy of healthy elderly

Effects of age and sex, and their interaction on the structural brain anatomy of healthy elderly were assessed thanks to a cross-sectional study of a cohort of 662 subjects aged from 63 to 75 years. T1- and T2-weighted MRI scans were acquired in each subject and further processed using a voxel-based approach that was optimized for the identification of the cerebrospinal fluid (CSF) compartment. Analysis of covariance revealed a classical neuroanatomy sexual dimorphism, men exhibiting larger gray matter (GM), white matter (WM), and CSF compartment volumes, together with larger WM and CSF fractions, whereas women showed larger GM fraction. GM and WM were found to significantly decrease with age, while CSF volume significantly increased. Tissue probability map analysis showed that the highest rates of GM atrophy in this age range were localized in primary cortices, the angular and superior parietal gyri, the orbital part of the prefrontal cortex, and in the hippocampal region. There was no significant interaction between "Sex" and "Age" for any of the tissue volumes, as well as for any of the tissue probability maps. These findings indicate that brain atrophy during the seventh and eighth decades of life is ubiquitous and proceeds at a rate that is not modulated by "Sex".

Comparison of different methodological implementations of voxel-based morphometry in neurodegenerative disease

Voxel-based morphometry (VBM) is a popular method for probing inter-group differences in brain morphology. Variation in the detailed implementation of the algorithm, however, will affect the apparent results of VBM analyses and in turn the inferences drawn about the anatomic expression of specific disease states. We qualitatively assessed group comparisons of 43 normal elderly control subjects and 51 patients with probable Alzheimer's disease, using five different VBM variations. Based on the known pathologic expression of the disease, we evaluated the biological plausibility of each. The use of a custom template and custom tissue class prior probability images (priors) produced inter-group comparison maps with greater biological plausibility than the use of the Montreal Neurological Institute (MNI) template and priors. We present a method for initializing the normalization to a custom template, and conclude that, when incorporated into the VBM processing chain, it yields the most biologically plausible inter-group differences of the five methods presented.

Pattern of cerebral hypoperfusion in Alzheimer disease and mild cognitive impairment measured with arterial spin-labeling MR imaging: initial experience

PURPOSE

To prospectively determine if pulsed arterial spin-labeling perfusion magnetic resonance (MR) imaging depicts regional cerebral hypoperfusion in subjects with Alzheimer disease (AD) and mild cognitive impairment (MCI), compared with perfusion in cognitively normal (CN) subjects, that is consistent with results of fluorodeoxyglucose (FDG) positron emission tomography (PET) and hexamethylpropyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT) studies of similar populations.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Twenty subjects with AD (13 men, seven women; mean age, 72.9 years), 18 with MCI (nine men, nine women; mean age, 73.3 years), and 23 CN subjects (10 men, 13 women; mean age, 72.9 years) underwent arterial spin-labeling and volumetric T1-weighted structural MR imaging. Perfusion images were coregistered to structural images, corrected for partial volume effects (PVEs) with information from the structural image to determine tissue content of perfusion voxels, and normalized to a study-specific template. Analyses of perfusion differences between groups, with and without corrections for PVEs, were performed on a voxel-by-voxel basis with a one-tailed fixed-effects analysis of covariance model adjusted for age. In addition, tests were performed with and without accounting for global perfusion.

RESULTS

The AD group showed significant regional hypoperfusion, compared with the CN group, in the right inferior parietal cortex extending into the bilateral posterior cingulate gyri (P <.001), bilateral superior and middle frontal gyri (P <.001), and left inferior parietal lobe (P=.007). When PVEs from underlying cortical gray matter atrophy were accounted for, the AD group still showed hypoperfusion in the right inferior parietal lobe extending into the bilateral posterior cingulate gyri (P <.001) and left (P=.003) and right (P=.012) middle frontal gyri. With a more liberal voxel-level threshold of P <.01, the MCI group showed significant regional hypoperfusion relative to the CN group in the inferior right parietal lobe (P=.046), similar to the region of greatest significance in the AD group.

CONCLUSION

Arterial spin-labeling MR imaging showed regional hypoperfusion with AD, in brain regions similar to those seen in FDG PET and HMPAO SPECT studies of similar populations; this hypoperfusion persists after accounting for underlying cortical gray matter atrophy.

Gray matter volume reduction in the chronic fatigue syndrome

The chronic fatigue syndrome (CFS) is a disabling disorder of unknown etiology. The symptomatology of CFS (central fatigue, impaired concentration, attention and memory) suggests that this disorder could be related to alterations at the level of the central nervous system. In this study, we have used an automated and unbiased morphometric technique to test whether CFS patients display structural cerebral abnormalities. We mapped structural cerebral morphology and volume in two cohorts of CFS patients (in total 28 patients) and healthy controls (in total 28 controls) from high-resolution structural magnetic resonance images, using voxel-based morphometry. Additionally, we recorded physical activity levels to explore the relation between severity of CFS symptoms and cerebral abnormalities. We observed significant reductions in global gray matter volume in both cohorts of CFS patients, as compared to matched control participants. Moreover, the decline in gray matter volume was linked to the reduction in physical activity, a core aspect of CFS. These findings suggest that the central nervous system plays a key role in the pathophysiology of CFS and point to a new objective and quantitative tool for clinical diagnosis of this disabling disorder.

Brain tissue damage in dementia with Lewy bodies: an in vivo diffusion tensor MRI study

The aim of the present study was to apply diffusion tensor MRI (DT-MRI), a quantitative MRI measure which reflects tissue organization, to dementia with Lewy bodies (DLB). DT-MRI scans were obtained from 15 patients with probable DLB and 10 sex- and age-matched healthy controls. Abnormalities were found in the corpus callosum, pericallosal areas and the frontal, parietal, occipital and, less prominently, temporal white matter of patients compared with controls. Abnormalities were also found in the caudate nucleus and the putamen. The average grey matter volume was lower in patients than in controls. These findings of concomitant grey matter atrophy and white matter abnormalities (as detected by DT-MRI) in regions with a high prevalence of long connecting fibre tracts might suggest the presence of neurodegeneration involving associative cortices. The modest involvement of the temporal lobe fits with the relative preservation of global neuropsychological measures and memory tasks in the early stage of DLB. The selective involvement of parietal, frontal and occipital lobes might explain some of the clinical and neuropsychological features of DLB, providing a possible distinctive marker for this disease. The abnormalities found in the subcortical grey matter may indicate that DLB and Parkinson's disease share a similar nigrostriatal involvement caused by common pathophysiological mechanisms.

Unified segmentation

A probabilistic framework is presented that enables image registration, tissue classification, and bias correction to be combined within the same generative model. A derivation of a log-likelihood objective function for the unified model is provided. The model is based on a mixture of Gaussians and is extended to incorporate a smooth intensity variation and nonlinear registration with tissue probability maps. A strategy for optimising the model parameters is described, along with the requisite partial derivatives of the objective function.

Preclinical detection of Alzheimer's disease: hippocampal shape and volume predict dementia onset in the elderly

Structural deformity of the hippocampus is characteristic of individuals with very mild and mild forms of dementia of the Alzheimer type (DAT). The purpose of this study was to determine whether a similar deformity of the hippocampus can predict the onset of dementia in nondemented elders. Using high dimensional diffeomorphic transformations of a neuroanatomical template, hippocampal volumes and surfaces were defined in 49 nondemented elders; the hippocampal surface was subsequently partitioned into three zones (i.e., lateral, superior and inferior-medial), which were proximal to the underlying CA1 subfield, CA2-4 subfields plus dentate gyrus, and subiculum, respectively. Annual clinical assessments using the Clinical Dementia Rating scale (CDR), where CDR 0 indicates no dementia and CDR 0.5 indicates very mild dementia, were then performed for a mean of 4.9 years (range 0.9-7.1 years) to monitor subjects who converted from CDR 0 to CDR 0.5. Inward variation of the lateral zone and left hippocampal volume significantly predicted conversion to CDR 0.5 in separate Cox proportional hazards models. When hippocampal surface variation and volume were included in a single model, inward variation of the lateral zone of the left hippocampal surface was selected as the only significant predictor of conversion. The pattern of hippocampal surface deformation observed in nondemented subjects who later converted to CDR 0.5 was similar to the pattern of hippocampal surface deformation previously observed to discriminate subjects with very mild DAT and nondemented subjects. These results suggest that inward deformation of the left hippocampal surface in a zone corresponding to the CA1 subfield is an early predictor of the onset of DAT in nondemented elderly subjects.

Volume changes in gray matter in first-episode neuroleptic-naive schizophrenic patients treated with risperidone

Structural neuroimaging techniques have consistently shown that treatment of schizophrenic patients with conventional antipsychotics causes an increase in basal ganglia volume. However, findings in schizophrenic patients treated with the newer atypical antipsychotic drugs are less consistently reported. To explore this issue, the authors used a whole-brain, unbiased, and automated technique for comparing brain structural features across scans in schizophrenic patients before and after a treatment with the atypical antipsychotic risperidone. T1-weighted images from 11 first-episode neuroleptic-naive schizophrenic patients were processed and analyzed for regions of interest (basal ganglia) by using optimized voxel-based morphometry. Scans were repeated after 3 months of continuous treatment with risperidone. Region of interest-based voxel-based morphometry analyses revealed increases in gray matter volume for the right and left caudate nuclei and for the left accumbens after the treatment with risperidone. Hence, in our sample of schizophrenic patients, treatment with risperidone was associated, in contrast to the findings for other atypical antipsychotics, with an increase in basal ganglia volume. Such discrepancy could be related to the pharmacodynamics of risperidone (the atypical antipsychotic showing the higher affinity for D2 receptors) and the rather high mean doses used in our study (ie, 6.05 mg/d).

Brain FDG PET study of normal aging in Japanese: effect of atrophy correction

PURPOSE

The aim of this study was to investigate the effects of atrophy correction on the results of 18F-fluorodeoxyglucose positron emission tomography (FDG PET) in the context of normal aging.

METHODS

Before the human study was performed, a Hoffman 3D brain phantom experiment was carried out in order to validate a newly developed correction method for partial volume effects (PVEs). Brain FDG PET was then performed in 139 healthy Japanese volunteers (71 men, 68 women; age 24-81 years). PET images were corrected for PVEs using grey matter volume, which was segmented from co-registered magnetic resonance images and convoluted with the spatial resolution of the PET scanner. We investigated the correlation between advancing age and relative regional FDG activity, which was normalised to the global activity before and after PVE correction using Statistical Parametric Mapping 99.

RESULTS

The PET image, when corrected for PVEs, provided more homogeneous tracer distribution in the whole phantom than in the original PET image. The human PET study of both sexes revealed significant negative correlations between age and relative FDG activity in the bilateral perisylvian and medial frontal areas before PVE correction. However, these negative correlations were largely resolved after PVE correction.

CONCLUSION

Correction for PVEs was effective in our FDG PET study. The reduction in FDG uptake with advancing age that was detected by FDG PET without PVE correction could be accounted for largely by an age-related cerebral volume loss in the bilateral perisylvian and medial frontal areas.

Non-rigid image registration: theory and practice

Image registration is an important enabling technology in medical image analysis. The current emphasis is on development and validation of application-specific non-rigid techniques, but there is already a plethora of techniques and terminology in use. In this paper we discuss the current state of the art of non-rigid registration to put on-going research in context and to highlight current and future clinical applications that might benefit from this technology. The philosophy and motivation underlying non-rigid registration is discussed and a guide to common terminology is presented. The core components of registration systems are described and outstanding issues of validity and validation are confronted.

Voxel-based analysis of MTR images: a method to locate gray matter abnormalities in patients at the earliest stage of multiple sclerosis

PURPOSE

To determine whether voxel-based analysis of magnetization transfer ratio (MTR) maps can provide evidence of a coherent pattern of gray matter (GM) macroscopic and microscopic tissue damage in patients at the earliest stage of multiple sclerosis (MS).

MATERIALS AND METHODS

We acquired GM MTR maps in 18 patients with clinically isolated syndrome suggestive of MS (CISSMS), and 18 sex- and age-matched healthy controls. We evaluated the clinical status of the patients using the MS functional composite score and the expanded disability status scale. A two-sample t-test (P <0.0001, k=20, uncorrected for height threshold) was used to compare GM MTR maps from patients and controls on a voxel-by-voxel basis. We then extracted data from regions with t-values above the statistical threshold to verify the significance of differences using a nonparametric Mann-Whitney U-test.

RESULTS

A between-groups comparison of GM maps revealed large abnormalities in the basal ganglia, including the bilateral thalamus, bilateral lenticular nucleus, bilateral head of caudate, and protuberance, and smaller abnormalities in the right insula, right BA 4, and left BA 40. The MTR measured in the left caudate and right insula was inversely correlated with duration following the first clinical event.

CONCLUSION

These results suggest that although MS is a multifocal demyelinating disease that affects white matter (WM), a pattern of tissue damage is present inside the GM involving predominantly basal ganglia at the earliest stage of the disease.

Age-related structural changes in the young adult brain shown by magnetic resonance diffusion tensor imaging

RATIONALE AND OBJECTIVE

Structure of the brain is generally thought to remain stationary over the course of young adulthood. However, there is some evidence that microstructural changes of the brain do occur during this period. Magnetic resonance diffusion tensor imaging (DTI) provides quantitative measures of structural changes in the brain. We used DTI to detect possible age-related structural changes in the brains of young adults.

MATERIALS AND METHODS

Twenty-five healthy adults in their 20s and 30s were studied using DTI. Maps of mean diffusivity and fractional anisotropy (FA) were created for subsequent histogram and region-of-interest analyses, and the results were correlated with the respective ages of the subjects.

RESULTS

The histogram analysis revealed a significant increase in the mean FA value (r = 0.407, P < .05) and a significant decrease in FA peak height (r = -0.578, P < .002) with increasing age. No age-related changes were observed in indices derived from mean diffusivity maps. Region-of-interest analysis showed no focal white matter regions with significant FA change.

CONCLUSION

Quantitative DTI revealed age-related structural changes in the brains of young adults. Changes on FA histograms observed in this study were considered to be related to changes in the relative volumes of gray and white matter and may represent maturational changes.