A comparison of automated segmentation and manual tracing for quantifying hippocampal and amygdala volumes

Effects of low-level sarin and cyclosarin exposure on hippocampal subfields in Gulf War Veterans

BACKGROUND

More than 100,000 US troops were potentially exposed to chemical warfare agents sarin (GB) and cyclosarin (GF) when an ammunition dump at Khamisiyah, Iraq was destroyed during the 1991 Gulf War (GW). We previously reported reduced hippocampal volume in GW veterans with suspected GB/GF exposure relative to matched, unexposed GW veterans estimated from 1.5T magnetic resonance images (MRI). Here we investigate, in a different cohort of GW veterans, whether low-level GB/GF exposure is associated with structural alterations in specific hippocampal subfields, estimated from 4T MRI.

METHODS

The Automatic Segmentation of Hippocampal Subfields (ASHS) technique was used to quantify CA1, CA2, CA3 and dentate gyrus (DG), and subiculum (SUB) subfields volumes from high-resolution T2-weighted images acquired on a 4T MR scanner in 56 GW veterans with suspected GB/GF exposure and 56 "matched" unexposed GW veterans (mean age 49±7 years).

RESULTS

GB/GF exposed veterans had smaller CA2 (p=0.003) and CA3/DG (p=0.01) subfield volumes compared to matched, unexposed GW veterans. There were no group difference in total hippocampal volume, quantified with FreeSurfer, and no dose-response relationship between estimated levels of GB/GF exposure and total hippocampal or subfield volume.

CONCLUSIONS

These findings extend our previous report of structural alterations in the hippocampi of GW veterans with suspected GB/GF exposure to volume changes in the CA2, CA3, and DG hippocampal subfields in a different cohort of GW veterans with suspected GB/GF exposure.

In vivo mapping of hippocampal subfields in mesial temporal lobe epilepsy: relation to histopathology

A particularly popular automated magnetic resonance imaging (MRI) hippocampal subfield mapping technique is the one described by Van Leemput et al. (2009: Hippocampus 19:549-557) that is currently distributed with FreeSurfer software. This method assesses the probabilistic locations of subfields based on a priori knowledge of subfield topology determined from high-field MRI. Many studies have applied this technique to conventionally acquired T1-weighted MRI data. In the present study, we investigated the relationship between this technique applied to conventional T1-weighted MRI data acquired at 3 T and postsurgical hippocampal histology in patients with medically intractable mesial temporal lobe epilepsy (mTLE) and hippocampal sclerosis (HS). Patients with mTLE (n = 82) exhibited significant volume loss of ipsilateral CA1, CA2-3, CA4-dentate gyrus (DG), subiculum, and fimbria relative to controls (n = 81). Histopathological analysis indicated that the most significant neuronal loss was observed in CA1, then CA4 and CA3, and more subtle neuronal loss in CA2, consistent with classical HS. Neuronal density of CA1 significantly correlated with MRI-determined volume of CA1, and increasingly so with CA2-3 and CA4-DG. Patients with increased HS based on histopathology had greater volume loss of the ipsilateral hippocampal regions on MRI. We conclude by suggesting that whilst time efficient and fully reproducible when applied to conventional single acquisition sequences, the use of the automated subfield technique described here may necessitate the application to multiacquisition high-resolution MR sequences for accurate delineation of hippocampal subfields.

Cortical thickness estimation in longitudinal stroke studies: A comparison of 3 measurement methods

There is considerable controversy about the causes of cognitive decline after stroke, with evidence for both the absence and coexistence of Alzheimer pathology. A reduction in cortical thickness has been shown to be an important biomarker for the progression of many neurodegenerative diseases, including Alzheimer's disease (AD). However, brain volume changes following stroke are not well described. Cortical thickness estimation presents an ideal way to detect regional and global post-stroke brain atrophy. In this study, we imaged a group of patients in the first month after stroke and at 3 months. We compared three methods of estimating cortical thickness on unmasked images: one surface-based (FreeSurfer) and two voxel-based methods (a Laplacian method and a registration method, DiRecT). We used three benchmarks for our analyses: accuracy of segmentation (especially peri-lesional performance), reproducibility, and biological validity. We found important differences between these methods in cortical thickness values and performance in high curvature areas and peri-lesional regions, but similar reproducibility metrics. FreeSurfer had less reliance on manual boundary correction than the other two methods, while reproducibility was highest in the Laplacian method. A discussion of the caveats for each method and recommendations for use in a stroke population is included. We conclude that both surface- and voxel-based methods are valid for estimating cortical thickness in stroke populations.

Comparison of human septal nuclei MRI measurements using automated segmentation and a new manual protocol based on histology

Septal nuclei, located in basal forebrain, are strongly connected with hippocampi and important in learning and memory, but have received limited research attention in human MRI studies. While probabilistic maps for estimating septal volume on MRI are now available, they have not been independently validated against manual tracing of MRI, typically considered the gold standard for delineating brain structures. We developed a protocol for manual tracing of the human septal region on MRI based on examination of neuroanatomical specimens. We applied this tracing protocol to T1 MRI scans (n=86) from subjects with temporal epilepsy and healthy controls to measure septal volume. To assess the inter-rater reliability of the protocol, a second tracer used the same protocol on 20 scans that were randomly selected from the 72 healthy controls. In addition to measuring septal volume, maximum septal thickness between the ventricles was measured and recorded. The same scans (n=86) were also analyzed using septal probabilistic maps and DARTEL toolbox in SPM. Results show that our manual tracing algorithm is reliable, and that septal volume measurements obtained via manual and automated methods correlate significantly with each other (p<.001). Both manual and automated methods detected significantly enlarged septal nuclei in patients with temporal lobe epilepsy in accord with a proposed compensatory neuroplastic process related to the strong connections between septal nuclei and hippocampi. Septal thickness, which was simple to measure with excellent inter-rater reliability, correlated well with both manual and automated septal volume, suggesting it could serve as an easy-to-measure surrogate for septal volume in future studies. Our results call attention to the important though understudied human septal region, confirm its enlargement in temporal lobe epilepsy, and provide a reliable new manual delineation protocol that will facilitate continued study of this critical region.

Physical activity level and medial temporal health in youth at ultra high-risk for psychosis

A growing body of evidence suggests that moderate to vigorous activity levels can affect quality of life, cognition, and brain structure in patients diagnosed with schizophrenia. However, physical activity has not been systematically studied during the period immediately preceding the onset of psychosis. Given reports of exercise-based neurogenesis in schizophrenia, understanding naturalistic physical activity levels in the prodrome may provide valuable information for early intervention efforts. The present study examined 29 ultra high-risk (UHR) and 27 matched controls to determine relationships between physical activity level, brain structure (hippocampus and parahippocampal gyrus), and symptoms. Participants were assessed with actigraphy for a 5-day period, MRI, and structured clinical interviews. UHR participants showed a greater percentage of time in sedentary behavior while healthy controls spent more time engaged in light to vigorous activity. There was a strong trend to suggest the UHR group showed less total physical activity. The UHR group exhibited smaller medial temporal volumes when compared with healthy controls. Total level of physical activity in the UHR group was moderately correlated with parahippocampal gyri bilaterally (right: r = .44, left: r = .55) and with occupational functioning (r = -.36; of negative symptom domain), but not positive symptomatology. Results suggest that inactivity is associated with medial temporal lobe health. Future studies are needed to determine if symptoms are driving inactivity, which in turn may be affecting the health of the parahippocampal structure and progression of illness. Although causality cannot be determined from the present design, these findings hold important implications for etiological conceptions and suggest promise for an experimental trial.

The neuroanatomical correlates of anxiety in a healthy population: differences between the State-Trait Anxiety Inventory and the Hamilton Anxiety Rating Scale

OBJECTIVES

The State-Trait Anxiety Inventory (STAI) and the Hamilton scale for anxiety (HARS) are two of the most important scales employed in clinical and psychological realms for the evaluation of anxiety. Although the reliability and sensibility of these scales are widely demonstrated there is an open debate on what exactly their scores reflect. Neuroimaging provides the potential to validate the quality and reliability of clinical scales through the identification of specific biomarkers. For this reason, we evaluated the neural correlates of these two scales in a large cohort of healthy individuals using structural neuroimaging methods.

CASE REPORT

Neuroimaging analysis included thickness/volume estimation of cortical and subcortical limbic structures, which were regressed on anxiety inventory scores with age and gender used for assessing discriminant validity. A total of 121 healthy subjects were evaluated. Despite the two anxiety scales, at a behavioral level, displaying significant correlations among them (HARS with STAI-state (r = 0.24; P = 0.006) and HARS with STAI-trait (r = 0.42; P < 0.001)), multivariate neuroimaging analyses demonstrated that anatomical variability in the anterior cingulate cortex was the best predictor of the HARS scores (all β's ≥ 0.31 and P's ≤ 0.01), whereas STAI-related measures did not show any significant relationship with regions of limbic circuits, but their scores were predicted by gender (all β's ≥ 0.23 and P's ≤ 0.02).

CONCLUSION

Although the purpose of HARS and STAI is to quantify the degree and characteristics of anxiety-like behaviors, our neuroimaging data indicated that these scales are neurobiologically different, confirming that their scores might reflect different aspects of anxiety: the HARS is more related to subclinical expression of anxiety disorders, whereas the STAI captures sub-dimensions of personality linked to anxiety.

Diagnosis of autism spectrum disorders using regional and interregional morphological features

This article describes a novel approach to identify autism spectrum disorder (ASD) utilizing regional and interregional morphological patterns extracted from structural magnetic resonance images. Two types of features are extracted to characterize the morphological patterns: (1) Regional features, which includes the cortical thickness, volumes of cortical gray matter, and cortical-associated white matter regions, and several subcortical structures extracted from different regions-of-interest (ROIs); (2) Interregional features, which convey the morphological change pattern between pairs of ROIs. We demonstrate that the integration of regional and interregional features via multi-kernel learning technique can significantly improve the classification performance of ASD, compared with using either regional or interregional features alone. Specifically, the proposed framework achieves an accuracy of 96.27% and an area of 0.9952 under the receiver operating characteristic curve, indicating excellent diagnostic power and generalizability. The best performance is achieved when both feature types are weighted approximately equal, indicating complementary between these two feature types. Regions that contributed the most to classification are in line with those reported in the previous studies, particularly the subcortical structures that are highly associated with human emotional modulation and memory formation. The autistic brains demonstrate a significant rightward asymmetry pattern particularly in the auditory language areas. These findings are in agreement with the fact that ASD is a behavioral- and language-related neurodevelopmental disorder. By concurrent consideration of both regional and interregional features, the current work presents an effective means for better characterization of neurobiological underpinnings of ASD that facilitates its identification from typically developing children.

Amount of lifetime video gaming is positively associated with entorhinal, hippocampal and occipital volume

Playing video games is a popular leisure activity among children and adults, and may therefore potentially influence brain structure. We have previously shown a positive association between probability of gray matter (GM) volume in the ventral striatum and frequent video gaming in adolescence. Here we set out to investigate structural correlates of video gaming in adulthood, as the effects observed in adolescents may reflect only a fraction of the potential neural long-term effects seen in adults. On magnetic resonance imaging (MRI) scans of 62 male adults, we computed voxel-based morphometry to explore the correlation of GM with the lifetime amount of video gaming (termed joystick years). We found a significant positive association between GM in bilateral parahippocamal region (entorhinal cortex) and left occipital cortex/inferior parietal lobe and joystick years (P<0.001, corrected for multiple comparisons). An exploratory analysis showed that the entorhinal GM volume can be predicted by the video game genres played, such as logic/puzzle games and platform games contributing positively, and action-based role-playing games contributing negatively. Furthermore, joystick years were positively correlated with hippocampus volume. The association of lifetime amount of video game playing with bilateral entorhinal cortex, hippocampal and occipital GM volume could reflect adaptive neural plasticity related to navigation and visual attention.

Development of hippocampal subfield volumes from 4 to 22 years

The hippocampus supports several important cognitive functions known to undergo substantial development during childhood and adolescence, for example, encoding and consolidation of vivid personal memories. However, diverging developmental effects on hippocampal volume have been observed across studies. It is possible that the inconsistent findings may attribute to varying developmental processes and functions related to different hippocampal subregions. Most studies to date have measured global hippocampal volume. We aimed to explore early hippocampal development both globally and regionally within subfields. Using cross-sectional 1.5 T magnetic resonance imaging data from 244 healthy participants aged 4-22 years, we performed automated hippocampal segmentation of seven subfield volumes; cornu ammonis (CA) 1, CA2/3, CA4/dentate gyrus (DG), presubiculum, subiculum, fimbria, and hippocampal fissure. For validation purposes, seven subjects were scanned at both 1.5 and 3 T, and all subfields except fimbria showed strong correlations across field strengths. Effects of age, left and right hemisphere, sex and their interactions were explored. Nonparametric local smoothing models (smoothing spline) were used to depict age-trajectories. Results suggested nonlinear age functions for most subfields where volume increases until 13-15 years, followed by little age-related changes during adolescence. Further, the results showed greater right than left hippocampal volumes that seemed to be augmenting in older age. Sex differences were also found for subfields; CA2/3, CA4/DG, presubiculum, subiculum, and CA1, mainly driven by participants under 13 years. These results provide a detailed characterization of hippocampal subfield development from early childhood.

Reduced thalamic volume in Parkinson disease with REM sleep behavior disorder: volumetric study

INTRODUCTION

REM sleep behavior disorder (RBD) is a common non motor feature of Parkinson's Disease (PD) affecting about half the patients with this disease. Distinct structural brain tissue abnormalities have been reported in several regions modulating REM sleep of the patients with idiopathic RBD. At the present time, there are no conventional MRI studies investigating patients with PD associated with RBD.

METHODS

Herein, we used voxel-based morphometry (VBM) to detect the neuroanatomical profile of PD patients with and without RBD. Optimized VBM was applied to the MRI brain images in 11 PD patients with RBD (PD-RBD), 11 PD patients without RBD (PD) and 18 age-and sex-matched controls. To corroborate VBM findings we used automated volumetric method (FreeSurfer) to quantify subcortical brain regions volumes. Patients and controls also underwent DAT-SPECT and cardiac MIBG scintigraphies.

RESULTS

The VBM analysis showed markedly reduced gray matter volume in the right thalamus of PD-RBD patients in comparison with PD patients and controls. Automatic thalamic segmentation in PD-RBD patients showed a bilaterally reduced thalamic volume as compared with PD patients or controls. All PD patients (with and without RBD) showed a reduced tracer uptake on DAT-SPECT and cardiac MIBG scintigraphies as compared to controls.

CONCLUSIONS

Our findings suggest that the presence of RBD symptoms in PD patients is associated with a reduced thalamic volume suggesting a pathophysiologic role of the thalamus in the complex circuit causing RBD.

Spontaneous mentalizing captures variability in the cortical thickness of social brain regions

Theory of mind (ToM)--or thinking about the mental states of others--is a cornerstone of successful everyday social interaction. However, the brain bases of ToM are most frequently measured via explicit laboratory tasks that pose direct questions about mental states (e.g. "In this story, what does Steve think Julia believes?"). Neuroanatomical measures may provide a way to explore the brain bases of individual differences in more naturalistic everyday mentalizing. In the current study, we examined the relation between cortical thickness and spontaneous ToM using the novel Spontaneous Theory of Mind Protocol (STOMP), which measures participants' spontaneous descriptions of the beliefs, emotions and goals of characters in naturalistic videos. We administered standard ToM tasks and the STOMP to young adults (aged 18-26 years) and collected structural magnetic resonance imaging data from a subset of these participants. The STOMP produced robust individual variability and was correlated with performance on traditional ToM tasks. Further, unlike the traditional ToM tasks, STOMP performance was related to cortical thickness for a set of brain regions that have been functionally linked to ToM processing. These findings offer novel insight into the brain bases of variability in naturalistic mentalizing performance, with implications for both typical and atypical populations.

Methods and considerations for longitudinal structural brain imaging analysis across development

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There have now been several longitudinal studies of structural brain development.

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We discuss current methods and analysis techniques in longitudinal MRI.

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We relate MRI measures to possible underlying physiological mechanisms.

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We encourage more open discussion amongst researchers regarding best practices.

Magnetic resonance imaging (MRI) has allowed the unprecedented capability to measure the human brain in vivo. This technique has paved the way for longitudinal studies exploring brain changes across the entire life span. Results from these studies have given us a glimpse into the remarkably extended and multifaceted development of our brain, converging with evidence from anatomical and histological studies. Ever-evolving techniques and analytical methods provide new avenues to explore and questions to consider, requiring researchers to balance excitement with caution. This review addresses what MRI studies of structural brain development in children and adolescents typically measure and how. We focus on measurements of brain morphometry (e.g., volume, cortical thickness, surface area, folding patterns), as well as measurements derived from diffusion tensor imaging (DTI). By integrating finding from multiple longitudinal investigations, we give an update on current knowledge of structural brain development and how it relates to other aspects of biological development and possible underlying physiological mechanisms. Further, we review and discuss current strategies in image processing, analysis techniques and modeling of brain development. We hope this review will aid current and future longitudinal investigations of brain development, as well as evoke a discussion amongst researchers regarding best practices.

Automated MRI parcellation of the frontal lobe

Examination of associations between specific disorders and physical properties of functionally relevant frontal lobe sub-regions is a fundamental goal in neuropsychiatry. Here, we present and evaluate automated methods of frontal lobe parcellation with the programs FreeSurfer(FS) and TOADS-CRUISE(T-C), based on the manual method described in Ranta et al. [2009]: Psychiatry Res 172:147-154 in which sulcal-gyral landmarks were used to manually delimit functionally relevant regions within the frontal lobe: i.e., primary motor cortex, anterior cingulate, deep white matter, premotor cortex regions (supplementary motor complex, frontal eye field, and lateral premotor cortex) and prefrontal cortex (PFC) regions (medial PFC, dorsolateral PFC, inferior PFC, lateral orbitofrontal cortex [OFC] and medial OFC). Dice's coefficient, a measure of overlap, and percent volume difference were used to measure the reliability between manual and automated delineations for each frontal lobe region. For FS, mean Dice's coefficient for all regions was 0.75 and percent volume difference was 21.2%. For T-C the mean Dice's coefficient was 0.77 and the mean percent volume difference for all regions was 20.2%. These results, along with a high degree of agreement between the two automated methods (mean Dice's coefficient = 0.81, percent volume difference = 12.4%) and a proof-of-principle group difference analysis that highlights the consistency and sensitivity of the automated methods, indicate that the automated methods are valid techniques for parcellation of the frontal lobe into functionally relevant sub-regions. Thus, the methodology has the potential to increase efficiency, statistical power and reproducibility for population analyses of neuropsychiatric disorders with hypothesized frontal lobe contributions.

A multi-scanner study of subcortical brain volume abnormalities in schizophrenia

Schizophrenia patients show significant subcortical brain abnormalities. We examined these abnormalities using automated image analysis software and provide effect size estimates for prospective multi-scanner schizophrenia studies. Subcortical and intracranial volumes were obtained using FreeSurfer 5.0.0 from high-resolution structural imaging scans from 186 schizophrenia patients (mean age±S.D.=38.9±11.6, 78% males) and 176 demographically similar controls (mean age±S.D.=37.5±11.2, 72% males). Scans were acquired from seven 3-Tesla scanners. Univariate mixed model regression analyses compared between-group volume differences. Weighted mean effect sizes (and number of subjects needed for 80% power at α=0.05) were computed based on the individual single site studies as well as on the overall multi-site study. Schizophrenia patients have significantly smaller intracranial, amygdala, and hippocampus volumes and larger lateral ventricle, putamen and pallidum volumes compared with healthy volunteers. Weighted mean effect sizes based on single site studies were generally larger than effect sizes computed based on analysis of the overall multi-site sample. Prospectively collected structural imaging data can be combined across sites to increase statistical power for meaningful group comparisons. Even when using similar scan protocols at each scanner, some between-site variance remains. The multi-scanner effect sizes provided by this study should help in the design of future multi-scanner schizophrenia imaging studies.

Sensitive periods of amygdala development: the role of maltreatment in preadolescence

The amygdala is vulnerable to stress-dependent disruptions in neural development. Animal models have shown that stress increases dendritic arborization leading to larger amygdala volumes. Human studies of early stress and amygdala volume, however, remain inconclusive. This study compared amygdala volume in adults with childhood maltreatment to that in healthy controls. Eighteen participants from a longitudinal cohort and 33 cross-sectional controls (17 M/34 F, 25.5±3.1 years) completed a structural magnetic resonance imagining scan and the Maltreatment and Abuse Chronology of Exposure scale. Random forest regression with conditional trees was used to assess relative importance of exposure to adversity at each age on amygdala, thalamic or caudate volume. Severity of exposure to adversity across age accounted for 27% of the variance in right amygdala volume. Peak sensitivity occurred at 10-11 years of age, and importance of exposure at this time was highly significant based on permutation tests (p=0.003). The regression model showed that exposure during this sensitive period resulted in steep dose-response function with maximal response to even modest levels of exposure. Subjects in the highest exposure quartile (MACE-11, range=11-54) had a 9.1% greater right amygdala volume than subjects in the lowest exposure quartile (MACE-11, ≤3.5). No associations emerged between age of exposure and volume of the left amygdala or bilateral caudate or thalamus. Severity of adversity experienced at age 10-11 contributed to larger right but not left amygdala volume in adulthood. Results provide preliminary evidence that the amygdala may have a developmental sensitive period in preadolescence.

The association of the BDNF Val66Met polymorphism and the hippocampal volumes in healthy humans: a joint meta-analysis of published and new data

BACKGROUND

The brain-derived neurotrophic factor (BDNF) Val66Met polymorphism (refSNP Cluster Report: rs6265) is a common and functionally relevant single nucleotide polymorphism (SNP). The gene itself, as well as the SNP rs6265, have been implicated in hippocampal learning and memory. However, imaging genetic studies have produced controversial results about the impact of this SNP on hippocampal volumes in healthy subjects.

METHODS

We examined the association between the rs6265 polymorphism and hippocampal volume in 643 healthy young subjects using automatic segmentation and subsequently included these data in a meta-analysis based on published studies with 5298 healthy subjects in total.

RESULTS

We found no significant association between SNP rs6265 and hippocampal volumes in our sample (g=0.05, p=0.58). The meta-analysis revealed a small, albeit significant difference in hippocampal volumes between genotype groups, such that Met-carriers had slightly smaller hippocampal volumes than Val/Val homozygotes (g=0.09, p=0.04), an association that was only evident when manual (g=0.22, p=0.01) but not automatic tracing approaches (g=0.04, p=0.38) were used. Studies using manual tracing showed evidence for publication bias and a significant decrease in effect size over the years with increasing sample sizes.

CONCLUSIONS

This study does not support the association between SNP rs6265 and hippocampal volume in healthy individuals. The weakly significant effect observed in the meta-analysis is mainly driven by studies with small sample sizes. In contrast, our original data and the meta-analysis of automatically segmented hippocampal volumes, which was based on studies with large samples sizes, revealed no significant genotype effect. Thus, meta-analyses of the association between rs6265 and hippocampal volumes should consider possible biases related to measuring technique and sample size.

Visualization of the amygdalo-hippocampal border and its structural variability by 7T and 3T magnetic resonance imaging

The amygdala and the hippocampus are two adjacent structures in the medial temporal lobe that have been broadly investigated in functional and structural neuroimaging due to their central importance in sensory perception, emotion, and memory. Exact demarcation of the amygdalo-hippocampal border (AHB) is, however, difficult in conventional structural imaging. Recent evidence suggests that, due to this difficulty, functional activation sites with high probability of being located in the hippocampus may erroneously be assigned to the amygdala, and vice versa. In the present study, we investigated the potential of ultra-high-field magnetic resonance imaging (MRI) in single sessions for detecting the AHB in humans. We show for the first time the detailed structure of the AHB as it can be visualized in T1-weighted 7T in vivo images at 0.5-mm(3) isotropic resolution. Compared to data acquired at 3T, 7T images revealed considerably more structural detail in the AHB region. Thus, we observed a striking inter-hemispheric and interindividual variability of the exact anatomical configuration of the AHB that points to the necessity of individual imaging of the AHB as a prerequisite for accurate anatomical assignment in this region. The findings of the present study demonstrate the usefulness of ultra-high-field structural MRI to resolve anatomical ambiguities of the human AHB. Highly accurate morphometric and functional investigations in this region at 7T may allow addressing such hitherto unexplored issues as whether the structural configuration of the AHB is related to functional differences in amygdalo-hippocampal interaction.

Hippocampal volume is decreased in adults with hypothyroidism

BACKGROUND

Thyroid hormones are important for the adult brain, particularly regions of the hippocampus including the dentate gyrus and CA1 and CA3 regions. The hippocampus is a thyroid hormone receptor-rich region of the brain involved in learning and memory. Consequently, alterations in thyroid hormone levels have been reported to impair hippocampal-associated learning and memory, synaptic plasticity, and neurogenesis. While these effects have been shown primarily in developing rats, as well as in adult rats, little is known about the effects in adult humans. There are currently no data regarding structural changes in the hippocampus as a result of adult-onset hypothyroidism. We aimed to establish whether hippocampal volume was reduced in patients with untreated adult-onset hypothyroidism compared to age-matched healthy controls.

METHODS

High-resolution magnetization-prepared rapid acquisition with gradient echo (MPRAGE) scans were performed on 11 untreated hypothyroid adults and 9 age-matched control subjects. Hypothyroidism was diagnosed based on increased levels of thyrotropin (TSH) and reduced levels of free thyroxine (fT4).

RESULTS

Volumetric analysis of the right and left hippocampal regions, using functional magnetic resonance imaging of the brain (FMRIB) integrated registration and segmentation tool (FIRST), demonstrated significant volume reduction in the right hippocampus in the hypothyroid patients relative to the control group.

CONCLUSIONS

These findings provide preliminary evidence that hypothyroidism results in structural deficits in the adult human brain. Decreases in volume in the right hippocampus were evident in patients with adult-onset overt hypothyroidism, supporting some of the findings in animal models.

A semi-automated pipeline for the segmentation of rhesus macaque hippocampus: validation across a wide age range

This report outlines a neuroimaging pipeline that allows a robust, high-throughput, semi-automated, template-based protocol for segmenting the hippocampus in rhesus macaque (Macaca mulatta) monkeys ranging from 1 week to 260 weeks of age. The semiautomated component of this approach minimizes user effort while concurrently maximizing the benefit of human expertise by requiring as few as 10 landmarks to be placed on images of each hippocampus to guide registration. Any systematic errors in the normalization process are corrected using a machine-learning algorithm that has been trained by comparing manual and automated segmentations to identify systematic errors. These methods result in high spatial overlap and reliability when compared with the results of manual tracing protocols. They also dramatically reduce the time to acquire data, an important consideration in large-scale neuroradiological studies involving hundreds of MRI scans. Importantly, other than the initial generation of the unbiased template, this approach requires only modest neuroanatomical training. It has been validated for high-throughput studies of rhesus macaque hippocampal anatomy across a broad age range.

Comparing manual and automatic segmentation of hippocampal volumes: reliability and validity issues in younger and older brains

We compared hippocampal volume measures obtained by manual tracing to automatic segmentation with FreeSurfer in 44 younger (20-30 years) and 47 older (60-70 years) adults, each measured with magnetic resonance imaging (MRI) over three successive time points, separated by four months. Retest correlations over time were very high for both manual and FreeSurfer segmentations. With FreeSurfer, correlations over time were significantly lower in the older than in the younger age group, which was not the case with manual segmentation. Pearson correlations between manual and FreeSurfer estimates were sufficiently high, numerically even higher in the younger group, whereas intra-class correlation coefficient (ICC) estimates were lower in the younger than in the older group. FreeSurfer yielded higher volume estimates than manual segmentation, particularly in the younger age group. Importantly, FreeSurfer consistently overestimated hippocampal volumes independently of manually assessed volume in the younger age group, but overestimated larger volumes in the older age group to a less extent, introducing a systematic age bias in the data. Age differences in hippocampal volumes were significant with FreeSurfer, but not with manual tracing. Manual tracing resulted in a significant difference between left and right hippocampus (right > left), whereas this asymmetry effect was considerably smaller with FreeSurfer estimates. We conclude that FreeSurfer constitutes a feasible method to assess differences in hippocampal volume in young adults. FreeSurfer estimates in older age groups should, however, be interpreted with care until the automatic segmentation pipeline has been further optimized to increase validity and reliability in this age group.

Hippocampal volume change measurement: quantitative assessment of the reproducibility of expert manual outlining and the automated methods FreeSurfer and FIRST

BACKGROUND

To measure hippocampal volume change in Alzheimer's disease (AD) or mild cognitive impairment (MCI), expert manual delineation is often used because of its supposed accuracy. It has been suggested that expert outlining yields poorer reproducibility as compared to automated methods, but this has not been investigated.

AIM

To determine the reproducibilities of expert manual outlining and two common automated methods for measuring hippocampal atrophy rates in healthy aging, MCI and AD.

METHODS

From the Alzheimer's Disease Neuroimaging Initiative (ADNI), 80 subjects were selected: 20 patients with AD, 40 patients with mild cognitive impairment (MCI) and 20 healthy controls (HCs). Left and right hippocampal volume change between baseline and month-12 visit was assessed by using expert manual delineation, and by the automated software packages FreeSurfer (longitudinal processing stream) and FIRST. To assess reproducibility of the measured hippocampal volume change, both back-to-back (BTB) MPRAGE scans available for each visit were analyzed. Hippocampal volume change was expressed in μL, and as a percentage of baseline volume. Reproducibility of the 1-year hippocampal volume change was estimated from the BTB measurements by using linear mixed model to calculate the limits of agreement (LoA) of each method, reflecting its measurement uncertainty. Using the delta method, approximate p-values were calculated for the pairwise comparisons between methods. Statistical analyses were performed both with inclusion and exclusion of visibly incorrect segmentations.

RESULTS

Visibly incorrect automated segmentation in either one or both scans of a longitudinal scan pair occurred in 7.5% of the hippocampi for FreeSurfer and in 6.9% of the hippocampi for FIRST. After excluding these failed cases, reproducibility analysis for 1-year percentage volume change yielded LoA of ±7.2% for FreeSurfer, ±9.7% for expert manual delineation, and ±10.0% for FIRST. Methods ranked the same for reproducibility of 1-year μL volume change, with LoA of ±218 μL for FreeSurfer, ±319 μL for expert manual delineation, and ±333 μL for FIRST. Approximate p-values indicated that reproducibility was better for FreeSurfer than for manual or FIRST, and that manual and FIRST did not differ. Inclusion of failed automated segmentations led to worsening of reproducibility of both automated methods for 1-year raw and percentage volume change.

CONCLUSION

Quantitative reproducibility values of 1-year microliter and percentage hippocampal volume change were roughly similar between expert manual outlining, FIRST and FreeSurfer, but FreeSurfer reproducibility was statistically significantly superior to both manual outlining and FIRST after exclusion of failed segmentations.

Hippocampal and amygdalar volumetric differences in pathological gambling: a preliminary study of the associations with the behavioral inhibition system

The behavioral inhibition system (BIS) and behavioral activation system (BAS) are hypothesized to underlie motivated behavior, relate to hippocampal and amygdalar function, and link to pathological gambling (PG). Prior studies have not investigated hippocampal and amygdalar volumes in PG and their relationships to BIS/BAS measures. Structural MRI scans and BIS/BAS and other clinical measures were obtained from 32 PG individuals and 47 healthy comparison (HC) individuals. Volumetric measures of the hippocampus and amygdala were assessed using FreeSurfer and related to BIS/BAS measures. PG relative to HC individuals demonstrated diminished volume in the left hippocampus and right amygdala and higher BIS and BAS scores. BIS scores were positively correlated with left hippocampal and left amygdalar volumes in PG individuals. The findings of relatively diminished hippocampal and amygdalar volumes in PG individuals resonate with findings from substance-dependent groups. Relationships between amygdalar and hippocampal volumes and BIS measures in PG suggest that individual differences in these structures may contribute to avoidance behaviors in PG.

Distinct neural systems underlying reduced emotional enhancement for positive and negative stimuli in early Alzheimer's disease

Emotional information is typically better remembered than neutral content, and previous studies suggest that this effect is subserved particularly by the amygdala together with its interactions with the hippocampus. However, it is not known whether amygdala damage affects emotional memory performance at immediate and delayed recall, and whether its involvement is modulated by stimulus valence. Moreover, it is unclear to what extent more distributed neocortical regions involved in e.g., autobiographical memory, also contribute to emotional processing. We investigated these questions in a group of patients with Alzheimer's disease (AD), which affects the amygdala, hippocampus and neocortical regions. Healthy controls (n = 14), patients with AD (n = 15) and its putative prodrome amnestic mild cognitive impairment (n = 11) completed a memory task consisting of immediate and delayed free recall of a list of positive, negative and neutral words. Memory performance was related to brain integrity in region of interest and whole-brain voxel-based morphometry analyses. In the brain-behavioral analyses, the left amygdala volume predicted the immediate recall of both positive and negative material, whereas at delay, left and right amygdala volumes were associated with performance with positive and negative words, respectively. Whole-brain analyses revealed additional associations between left angular gyrus integrity and the immediate recall of positive words as well as between the orbitofrontal cortex and the delayed recall of negative words. These results indicate that emotional memory impairments in AD may be underpinned by damage to regions implicated in emotional processing as well as frontoparietal regions, which may exert their influence via autobiographical memories and organizational strategies.

Neurobiological effects of physical exercise in schizophrenia: a systematic review

PURPOSE

The aim of the present systematic review was to provide a summary of neurobiological effects of physical exercise for people with schizophrenia.

METHODS

A systematic review was conducted in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement. Searches were conducted up to April 2013 across three databases: Medline, PsycINFO, and Embase. A methodological quality assessment using the Downs and Black Quality Index was carried out with all of the included studies.

RESULTS

Of the 654 initial data search results, two studies reported in 3 articles including 48 patients (six women) with schizophrenia, met the eligibility criteria. The methodological quality of each study was high. Data on hippocampal volume changes following physical exercise were conflicting while physical exercise-induced changes in other brain areas were absent. Increases in hippocampal volume following physical exercise were correlated with improvements in aerobic fitness and short-term memory.

CONCLUSIONS

Future research is needed to investigate whether brain health in people with schizophrenia is activity-dependent. Additionally, research that considers the neurobiological mechanisms and associated functional outcomes of physical exercise in individuals with schizophrenia is required.

IMPLICATIONS FOR REHABILITATION

Understanding the neurobiological effects of physical exercise in patients with schizophrenia may contribute to the development of new rehabilitation strategies. There is currently insufficient evidence to determine if physical exercise has a beneficial influence on the brain health of people with schizophrenia.

Interactive effects of chronic cigarette smoking and age on hippocampal volumes

BACKGROUND

Previous cross-sectional MRI studies with healthy, young-to-middle-aged adults reported no significant differences between smokers and non-smokers on total hippocampal volume. However, these studies did not specifically test for greater age-related volume loss in the total hippocampus or hippocampal subregions in smokers, and did they did not examine relationships between hippocampal and subfield volumes and episodic learning and memory performance.

METHODS

Healthy, young-to-middle-aged (45 ± 12 years of age) smokers (n=39) and non-smokers (n=43) were compared on total hippocampal and subfield volumes derived from high-resolution 4 Tesla MRI, emphasizing testing for greater age-related volume losses in smokers. Associations between hippocampal volumes and measures of episodic learning and memory were examined.

RESULTS

Smokers showed significantly smaller volumes, as well as greater volume loss with increasing age than non-smokers in the bilateral total hippocampus and multiple subfields. In smokers, greater pack-years were associated with smaller volumes of the total hippocampus, presubiculum, and subiculum. In the entire cohort, performance on measures of learning and memory was related to larger total hippocampal and several subfield volumes, predominately in the left hemisphere.

CONCLUSIONS

Chronic cigarette smoking in this young-to-middle aged cohort was associated with smaller total hippocampal and subfield volumes, which were exacerbated by advancing age. Findings also indicated an adverse smoking dose/duration response (i.e., pack-years) with total hippocampal and select subfield volumes. These hippocampal volume abnormalities in smokers may be related to the deficiencies in episodic learning and memory in young-to-middle-aged smokers reported in previous studies.

Measurement and genetics of human subcortical and hippocampal asymmetries in large datasets

Functional and anatomical asymmetries are prevalent features of the human brain, linked to gender, handedness, and cognition. However, little is known about the neurodevelopmental processes involved. In zebrafish, asymmetries arise in the diencephalon before extending within the central nervous system. We aimed to identify genes involved in the development of subtle, left-right volumetric asymmetries of human subcortical structures using large datasets. We first tested the feasibility of measuring left-right volume differences in such large-scale samples, as assessed by two automated methods of subcortical segmentation (FSL|FIRST and FreeSurfer), using data from 235 subjects who had undergone MRI twice. We tested the agreement between the first and second scan, and the agreement between the segmentation methods, for measures of bilateral volumes of six subcortical structures and the hippocampus, and their volumetric asymmetries. We also tested whether there were biases introduced by left-right differences in the regional atlases used by the methods, by analyzing left-right flipped images. While many bilateral volumes were measured well (scan-rescan r = 0.6-0.8), most asymmetries, with the exception of the caudate nucleus, showed lower repeatabilites. We meta-analyzed genome-wide association scan results for caudate nucleus asymmetry in a combined sample of 3,028 adult subjects but did not detect associations at genome-wide significance (P < 5 × 10(-8) ). There was no enrichment of genetic association in genes involved in left-right patterning of the viscera. Our results provide important information for researchers who are currently aiming to carry out large-scale genome-wide studies of subcortical and hippocampal volumes, and their asymmetries.

Diagnostic accuracy of markers for prodromal Alzheimer's disease in independent clinical series

OBJECTIVE

To capitalize on data from different clinical series to compare sensitivity and specificity of individual biomarkers for predicting mild cognitive impairment (MCI) progression to Alzheimer's disease (AD).

METHODS

Medial temporal atrophy, cortical hypometabolism, and cerebrospinal fluid biomarkers were assessed in 18 patients with mild cognitive impairment (MCI) with prodromal AD (pAD; conversion time, 26 ± 12 months) and 18 stable MCI (sMCI) patients from the Translational Outpatient Memory Clinic cohort, as well as in 24 pAD patients (conversion time, 36 ± 12 months) and 33 sMCI patients from the Alzheimer's Disease Neuroimaging Initiative cohort. Medial temporal atrophy was measured by manual, semi-automated, and automated hippocampal volumetry; cortical hypometabolism was measured using several indices of AD-related hypometabolism pattern; and cerebrospinal fluid markers were amyloid β (Aβ)42 and total tau protein concentrations. For each biomarker, sensitivity for pAD, specificity for sMCI, and diagnostic accuracy were computed.

RESULTS

Sensitivity to predict MCI conversion to AD in the Alzheimer's Disease Neuroimaging Initiative and Translational Outpatient Memory Clinic cohorts was 79% and 94% based on Aβ42, 46% and 28% based on hippocampal volumes, 33% to 66% and 56% to 78% based on different hypometabolism indices, and 46% and 61% based on total tau levels, respectively. Specificity to exclude sMCI was 27% and 50% based on Aβ42, 76% and 94% based on hippocampal volumes, 58% to 67% and 55% to 83% based on different hypometabolism indices, and 61% and 83% based on total tau levels, respectively.

CONCLUSIONS

Current findings suggest that Aβ42 concentrations and hippocampal volumes may be used in combination to best identify pAD.

Development and validation of an unsupervised scoring system (Autonomate) for skin conductance response analysis

The skin conductance response (SCR) is increasingly being used as a measure of sympathetic activation concurrent with neuroscience measurements. We present a method of automated analysis of SCR data in the contexts of event-related cognitive tasks and nonspecific responding to complex stimuli. The primary goal of the method is to accurately measure the classical trough-to-peak amplitude of SCR in a fashion closely matching manual scoring. To validate the effectiveness of the method in event-related paradigms, three archived datasets were analyzed by two manual raters, the fully-automated method (Autonomate), and three alternative software packages. Further, the ability of the method to score non-specific responses to complex stimuli was validated against manual scoring. Results indicate high concordance between fully-automated and computer-assisted manual scoring methods. Given that manual scoring is error prone, subject to bias, and time consuming, the automated method may increase the efficiency and accuracy of SCR data analysis.

The influence of puberty on subcortical brain development

Puberty is characterized by hormonal, physical and psychological transformation. The human brain undergoes significant changes between childhood and adulthood, but little is known about how puberty influences its structural development. Using a longitudinal sample of 711 magnetic resonance imaging scans from 275 individuals aged 7–20 years, we examined how subcortical brain regions change in relation to puberty. Our regions of interest included the amygdala, hippocampus and corpus striatum including the nucleus accumbens (NA), caudate, putamen and globus pallidus (GP). Pubertal development was significantly related to structural volume in all six regions in both sexes. Pubertal development and age had both independent and interactive influences on volume for the amygdala, hippocampus and putamen in both sexes, and the caudate in females. There was an interactive puberty-by-age effect on volume for the NA and GP in both sexes, and the caudate in males. These findings suggest a significant role for puberty in structural brain development.

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Subcortical regions continue to develop through puberty in females and males.

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The developmental trajectories vary between subcortical regions.

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Puberty and age have independent and interactive influences on this development.

Reduced thalamic volumes in major depressive disorder

Altered function in the limbic-cortical-striatial-pallidal-thalamic (LCSPT) circuit has been implicated in the pathophysiology of major depressive disorder (MDD). This study evaluated volumetric differences in subcortical volumes between depressed subjects with MDD (N=142), subjects with MDD in remission (N=72), and healthy controls (N=169). Participants underwent magnetic resonance imaging (MRI) scanning, and subcortical volumes were extracted using FMRIB's Integrated Registration and Segmentation Tool (FIRST), University of Oxford, UK. The depressed MDD subjects exhibited significantly smaller volumes in the bilateral thalamus and hippocampus compared to control subjects, and the differences in the bilateral thalamus remained significant after controlling for total intracranial volume. In a smaller subset of healthy controls and depressed MDD subjects matched to the remitted MDD subjects, significant differences in volume were observed across groups in the bilateral thalamus, as well as the right lateralized caudate, hippocampus, and pallidum; these were primarily accounted for by differences between the depressed MDD subjects versus both the remitted and healthy subjects, though none of these changes remained significant after controlling for total intracranial volume (TIV). Volumetric reductions in the thalamus and hippocampus may contribute to dysfunction within subcortical-cortical networks, consistent with previous evidence of metabolic and hemodynamic abnormalities in these regions in MDD.

Amygdala volume linked to individual differences in mental state inference in early childhood and adulthood

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Children and adults interpreted cognitive and affective states from pictures of eyes.

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For children, a larger amygdala was correlated with better cognitive mental state inference.

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For adults, a larger amygdala was correlated with better affective mental state inference.

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Amygdala size was not related to performance on story-based mental inference tasks.

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The amygdala's role in social cognition is task-specific and may change with age.

We investigated the role of the amygdala in mental state inference in a sample of adults and in a sample of children aged 4 and 6 years. This period in early childhood represents a time when mentalizing abilities undergo dramatic changes. Both children and adults inferred mental states from pictures of others’ eyes, and children also inferred the mental states of others from stories (e.g., a false belief task). We also collected structural MRI data from these participants, to determine whether larger amygdala volumes (controlling for age and total gray matter volume) were related to better face-based and story-based mentalizing. For children, larger amygdala volumes were related to better face-based, but not story-based, mentalizing. In contrast, in adults, amygdala volume was not related to face-based mentalizing. We next divided the face-based items into two subscales: cognitive (e.g., thinking, not believing) versus affective (e.g., friendly, kind) items. For children, performance on cognitive items was positively correlated with amygdala volume, but for adults, only performance on affective items was positively correlated with amygdala volume. These results indicate that the amygdala's role in mentalizing may be specific to face-based tasks and that the nature of its involvement may change over development.

Increased cortical thickness in a frontoparietal network in social anxiety disorder

Social anxiety disorder (SAD) is the second leading anxiety disorder. On the functional neurobiological level, specific brain regions involved in the processing of anxiety-laden stimuli and in emotion regulation have been shown to be hyperactive and hyper-responsive in SAD such as amygdala, insula and orbito- and prefrontal cortex. On the level of brain structure, prior studies on anatomical differences in SAD resulted in mixed and partially contradictory findings. Based on previous functional and anatomical models of SAD, this study examined cortical thickness in structural magnetic resonance imaging data of 46 patients with SAD without comorbidities (except for depressed episode in one patient) compared with 46 matched healthy controls in a region of interest-analysis and in whole-brain. In a theory-driven ROI-analysis, cortical thickness was increased in SAD in left insula, right anterior cingulate and right temporal pole. Furthermore, the whole-brain analysis revealed increased thickness in right dorsolateral prefrontal and right parietal cortex. This study detected no regions of decreased cortical thickness or brain volume in SAD. From the perspective of brain networks, these findings are in line with prior functional differences in salience networks and frontoparietal networks associated with executive-controlling and attentional functions.

Widespread reductions in gray matter volume in depression

Abnormalities in functional limbic–anterior cingulate–prefrontal circuits associated with emotional reactivity, evaluation and regulation have been implicated in the pathophysiology of major depressive disorder (MDD). However, existing knowledge about structural alterations in depression is equivocal and based on cohorts of limited sample size. This study used voxel-based morphometry (VBM) and surface-based cortical thickness to investigate the structure of these circuits in a large and well-characterized patient cohort with MDD.

Non-geriatric MDD outpatients (n = 102) and age- and gender-matched healthy control participants (n = 34) provided T1-weighted magnetic resonance imaging data during their baseline visit as part of the International Study to Predict Optimized Treatment for Depression. Whole-brain VBM volumetric and surface-based cortical thickness assessments were performed voxel-wise and compared (at p < 0.05 corrected for multiple comparisons) between the MDD and control groups.

MDD participants had reduced gray matter volume in the anterior cingulate cortex, regions of the prefrontal circuits, including dorsolateral and dorsomedial prefrontal cortices, and lateral and medial orbitofrontal cortices, but not in limbic regions. Additional reductions were observed cortically in the posterior temporal and parieto-occipital cortices and, subcortically in the basal ganglia and cerebellum. Focal cortical thinning in the medial orbitofrontal cortex was also observed for the MDD group. These alterations in volume and cortical thickness were not associated with severity of depressive symptoms.

The findings demonstrate that widespread gray matter structural abnormalities are present in a well-powered study of patients with depression. The patterns of gray matter loss correspond to the same brain functional network regions that were previously established to be abnormal in MDD, which may support an underlying structural abnormality for these circuits.

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Focal gray matter volume decrease in depression exceeded loss via aging 11–50 years.

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Gray matter differences were found in regions with established roles in depression.

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Structural change findings support the idea of depression as a network abnormality.

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Hippocampal gray matter volume loss likely has no role in non-geriatric depression.

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Amygdala gray matter volume loss likely plays no role in depression pathophysiology.

Detection of hippocampal atrophy in patients with temporal lobe epilepsy: a 3-Tesla MRI shape

In patients with mesial temporal lobe epilepsy (MTLE), brain MRI often detects hippocampal sclerosis (HS). Almost half of patients with MTLE do not show any hippocampal damage on visual or volumetric assessment. Here, we wished to prospectively assess 65 patients with MTLE (41 women, mean age: 39±10years, range: 21-69; right (12/65 patients) (MRI-negative) nMTLE; right (14/65 patients) (MRI-positive with HS) pMTLE; left (24/65 patients) nMTLE; and left (15/65 patients) pMTLE) using shape analysis (SA). There were significant differences among pMTLE versus nMTLE for age at seizure onset (20.2±12.8 vs. 31.8±16.7years; p=.0029), duration of epilepsy (14.6±12.7 vs. 21.3±9.6years; p=.0227), risk of refractoriness (p=.0067), frequency of antecedent febrile convulsions (FCs) (p<.001), as well as a history of epilepsy or FCs (p=.0104). All the subjects underwent the same 3-Tesla MRI protocol. Shape analysis of hippocampal formation was conducted comparing each group versus 44 matched controls. In all four subgroups, SA detected a significant atrophy in the corresponding hippocampus that coincided with the epileptogenic area. The damage was significantly more severe in patients with pMTLE (F value: 5.00) than in subgroups with nMTLE (F value: 3.50) and mainly corresponded to the CA1 subregion and subiculum. In the patients with MTLE, SA detects hippocampal damage that lateralizes with the epileptogenic area. Such damage is most prominent in the CA1 subregion and subiculum that are crucial in the pathogenesis of MTLE.

Socioeconomic deprivation and cortical morphology: psychological, social, and biological determinants of ill health study

OBJECTIVE

Neighborhood-level socioeconomic deprivation has been associated with poor cognitive function pertaining to language and the executive control. Few studies have explored the cortical morphology of regions most commonly associated with these functions. The aim of this study was to examine the association between neighborhood-level deprivation and the morphology of cortical regions associated with language and executive control in adults.

METHODS

Using a cross-sectional study design, we compared the cortical morphology of 42 neurologically healthy adult men from the least deprived and most deprived neighborhoods of Glasgow. We performed surface-based morphometry on 3-T structural magnetic resonance imaging (MRI) images to extract the cortical morphology--volume, thickness (CT), and surface area (SA) of regions commonly associated with language and executive control. Cortical morphology was compared between the two groups. We used mediation analysis to examine whether cardiometabolic risk factors mediated the relationship between deprivation status and cortical morphology.

RESULTS

Intracranial volume and mean total CT did not differ between groups. The deprived group had significantly smaller left posterior parietal cortex SA (Cohen d = 0.89) and fusiform cortex SA (Cohen d = 1.05). They also had thinner left Wernicke's area (Cohen d =0.93) and its right homologue (Cohen d = 1.12). Among the cardiometabolic markers, a composite factor comprising inflammatory markers mediated the relationship between deprivation status and Wernicke's area CT.

CONCLUSIONS

A group of neurologically healthy men from deprived neighborhoods showed significantly smaller cortical morphology--both SA and CT--in regions of the brain pertaining to language and executive function. We provide additional evidence of a relationship between socioeconomic deprivation and cortical morphology.

History of mild traumatic brain injury is associated with deficits in relational memory, reduced hippocampal volume, and less neural activity later in life

Evidence suggests that a history of head trauma is associated with memory deficits later in life. The majority of previous research has focused on moderate-to-severe traumatic brain injury (TBI), but recent evidence suggests that even a mild TBI (mTBI) can interact with the aging process and produce reductions in memory performance. This study examined the association of mTBI with memory and the brain by comparing young and middle-aged adults who have had mTBI in their recent (several years ago) and remote (several decades ago) past, respectively, with control subjects on a face-scene relational memory paradigm while they underwent functional magnetic resonance imaging (fMRI). Hippocampal volumes were also examined from high-resolution structural images. Results indicated middle-aged adults with a head injury in their remote past had impaired memory compared to gender, age, and education matched control participants, consistent with previous results in the study of memory, aging, and TBI. The present findings extended previous results by demonstrating that these individuals also had smaller bilateral hippocampi, and had reduced neural activity during memory performance in cortical regions important for memory retrieval. These results indicate that a history of mTBI may be one of the many factors that negatively influence cognitive and brain health in aging.

A longitudinal study of brain atrophy over two years in community-dwelling older individuals

Most previous neuroimaging studies of age-related brain structural changes in older individuals have been cross-sectional and/or restricted to clinical samples. The present study of 345 community-dwelling non-demented individuals aged 70-90years aimed to examine age-related brain volumetric changes over two years. T1-weighted magnetic resonance imaging scans were obtained at baseline and at 2-year follow-up and analyzed using the FMRIB Software Library and FreeSurfer to investigate cortical thickness and shape and volumetric changes of subcortical structures. The results showed significant atrophy across much of the cerebral cortex with bilateral transverse temporal regions shrinking the fastest. Atrophy was also found in a number of subcortical structures, including the CA1 and subiculum subfields of the hippocampus. In some regions, such as left and right entorhinal cortices, right hippocampus and right precentral area, the rate of atrophy increased with age. Our analysis also showed that rostral middle frontal regions were thicker bilaterally in older participants, which may indicate its ability to compensate for medial temporal lobe atrophy. Compared to men, women had thicker cortical regions but greater rates of cortical atrophy. Women also had smaller subcortical structures. A longer period of education was associated with greater thickness in a number of cortical regions. Our results suggest a pattern of brain atrophy with non-demented people that resembles a less extreme form of the changes associated with Alzheimer's disease (AD).

Exercise therapy, cardiorespiratory fitness and their effect on brain volumes: a randomised controlled trial in patients with schizophrenia and healthy controls

The objective of this study was to examine exercise effects on global brain volume, hippocampal volume, and cortical thickness in schizophrenia patients and healthy controls. Irrespective of diagnosis and intervention, associations between brain changes and cardiorespiratory fitness improvement were examined. Sixty-three schizophrenia patients and fifty-five healthy controls participated in this randomised controlled trial. Global brain volumes, hippocampal volume, and cortical thickness were estimated from 3-Tesla MRI scans. Cardiorespiratory fitness was assessed with a cardiopulmonary ergometer test. Subjects were assigned exercise therapy or occupational therapy (patients) and exercise therapy or life-as-usual (healthy controls) for six months 2h weekly. Exercise therapy effects were analysed for subjects who were compliant at least 50% of sessions offered. Significantly smaller baseline cerebral (grey) matter, and larger third ventricle volumes, and thinner cortex in most areas of the brain were found in patients versus controls. Exercise therapy did not affect global brain and hippocampal volume or cortical thickness in patients and controls. Cardiorespiratory fitness improvement was related to increased cerebral matter volume and lateral and third ventricle volume decrease in patients and to thickening in the left hemisphere in large areas of the frontal, temporal and cingulate cortex irrespective of diagnosis. One to 2h of exercise therapy did not elicit significant brain volume changes in patients or controls. However, cardiorespiratory fitness improvement attenuated brain volume changes in schizophrenia patients and increased thickness in large areas of the left cortex in both schizophrenia patients and healthy controls.

Human amygdala volume is predicted by common DNA variation in the stathmin and serotonin transporter genes

Despite the relevance of changes in amygdala volume to psychiatric illnesses and its heritability in both health and disease, the influence of common genetic variation on amygdala morphology remains largely unexplored. In the present study, we investigated the influence of a number of novel genetic variants on amygdala volume in 139 neurologically healthy individuals of European descent. Amygdala volume was significantly associated with allelic variation in the stathmin (STMN1) and serotonin transporter (SLC6A4) genes, which have been linked to healthy and disordered affective processing. These results were replicated across both manual and automated methods of amygdala parcellation, although manual tracing showed stronger effects, providing a cautionary note to studies relying on automated parcellation methods. Future studies will need to determine whether amygdala volume mediates the impact of stathmin and serotonin transporter gene variants on normal and dysfunctional emotion processing.

Structural development of the hippocampus and episodic memory: developmental differences along the anterior/posterior axis

The hippocampus is critically involved in episodic memory, yet relatively little is known about how the development of this structure contributes to the development of episodic memory during middle to late childhood. Previous research has inconsistently reported associations between hippocampal volume and episodic memory performance during this period. We argue that this inconsistency may be due to assessing the hippocampus as a whole, and propose to examine associations separately for subregions along the longitudinal axis of the hippocampus. In the present study, we examined age-related differences in volumes of the hippocampal head, body, and tail, and collected episodic memory measures in children ages 8-11 years and young adults (N = 62). We found that adults had a smaller right hippocampal head, larger hippocampal body bilaterally, and smaller right hippocampal tail compared with children. In adults, but not in children, better episodic memory performance was associated with smaller right hippocampal head and larger hippocampal body. In children, but not in adults, better episodic memory was associated with larger left hippocampal tail. Overall, the results suggest that protracted development of hippocampal subregions contribute to age-related differences in episodic memory.

Bayesian Parameter Estimation and Segmentation in the Multi-Atlas Random Orbit Model

This paper examines the multiple atlas random diffeomorphic orbit model in Computational Anatomy (CA) for parameter estimation and segmentation of subcortical and ventricular neuroanatomy in magnetic resonance imagery. We assume that there exist multiple magnetic resonance image (MRI) atlases, each atlas containing a collection of locally-defined charts in the brain generated via manual delineation of the structures of interest. We focus on maximum a posteriori estimation of high dimensional segmentations of MR within the class of generative models representing the observed MRI as a conditionally Gaussian random field, conditioned on the atlas charts and the diffeomorphic change of coordinates of each chart that generates it. The charts and their diffeomorphic correspondences are unknown and viewed as latent or hidden variables. We demonstrate that the expectation-maximization (EM) algorithm arises naturally, yielding the likelihood-fusion equation which the a posteriori estimator of the segmentation labels maximizes. The likelihoods being fused are modeled as conditionally Gaussian random fields with mean fields a function of each atlas chart under its diffeomorphic change of coordinates onto the target. The conditional-mean in the EM algorithm specifies the convex weights with which the chart-specific likelihoods are fused. The multiple atlases with the associated convex weights imply that the posterior distribution is a multi-modal representation of the measured MRI. Segmentation results for subcortical and ventricular structures of subjects, within populations of demented subjects, are demonstrated, including the use of multiple atlases across multiple diseased groups.

Mapping subcortical brain maturation during adolescence: evidence of hemisphere- and sex-specific longitudinal changes

Early to mid-adolescence is an important developmental period for subcortical brain maturation, but longitudinal studies of these neurodevelopmental changes are lacking. The present study acquired repeated magnetic resonance images from 60 adolescent subjects (28 female) at ages 12.5 and 16.5 years to map changes in subcortical structure volumes. Automated segmentation techniques optimized for longitudinal measurement were used to delineate volumes of the caudate, putamen, nucleus accumbens, pallidum, hippocampus, thalamus and the whole brain. Amygdala volumes were described using manual tracing methods. The results revealed heterogeneous maturation across the regions of interest (ROIs), and change was differentially moderated by sex and hemisphere. The caudate, thalamus and putamen declined in volume, more for females relative to males, and decreases in the putamen and thalamus were greater in the left hemisphere. The pallidum increased in size, but more so in the left hemisphere. While the left nucleus accumbens increased in size, the right accumbens decreased in size over the follow-up period. Increases in hippocampal volume were greater in the right hemisphere. While amygdala volume did not change over time, the left hemisphere was consistently larger than the right. These results suggest that subcortical brain development from early to middle adolescence is characterized by striking hemispheric specialization and sexual dimorphisms, and provide a framework for interpreting normal and abnormal changes in cognition, affect and behavior. Moreover, the differences in findings compared to previous cross-sectional research emphasize the importance of within-subject assessment of brain development during adolescence.

Imaging patients with psychosis and a mouse model establishes a spreading pattern of hippocampal dysfunction and implicates glutamate as a driver

VIDEO ABSTRACT

The hippocampus in schizophrenia is characterized by both hypermetabolism and reduced size. It remains unknown whether these abnormalities are mechanistically linked. Here we addressed this question by using MRI tools that can map hippocampal metabolism and structure in patients and mouse models. In at-risk patients, hypermetabolism was found to begin in CA1 and spread to the subiculum after psychosis onset. CA1 hypermetabolism at baseline predicted hippocampal atrophy, which occurred during progression to psychosis, most prominently in similar regions. Next, we used ketamine to model conditions of acute psychosis in mice. Acute ketamine reproduced a similar regional pattern of hypermetabolism, while repeated exposure shifted the hippocampus to a hypermetabolic basal state with concurrent atrophy and pathology in parvalbumin-expressing interneurons. Parallel in vivo experiments using the glutamate-reducing drug LY379268 and direct measurements of extracellular glutamate showed that glutamate drives both neuroimaging abnormalities. These findings show that hippocampal hypermetabolism leads to atrophy in psychotic disorder and suggest glutamate as a pathogenic driver.

Increased prefrontal cortical thickness is associated with enhanced abilities to regulate emotions in PTSD-free women with borderline personality disorder

Previous studies suggest that amygdala, insula and prefrontal cortex (PFC) disintegrity play a crucial role in the failure to adequately regulate emotions in Borderline Personality Disorder (BPD). However, prior results are confounded by the high rate of comorbidity with Posttraumatic Stress Disorder (PTSD), which itself has been associated with changes in frontolimbic circuitry. We thus scrutinized the link between PFC, amygdala, insula, and the ability to regulate emotions, contrasting 17 women with BPD without comorbid PTSD to 27 non-clinical control women and in addition to those with BPD and PTSD (n = 14). BPD women without PTSD, but not those with comorbid PTSD, had increased cortical thickness in the dorsolateral PFC (DLPFC) in comparison to control women. Furthermore, cortical thickness in the DLPFC of BPD women without PTSD positively correlated with emotion regulation scores and furthermore was positively associated with amygdala volume, as well as cortical thickness of the insula. Our findings highlight the importance of disentangling the impact of BPD and PTSD on the brain and suggest possible compensatory mechanisms for the impaired emotion regulation in BPD women without PTSD.

The effect of threat on novelty evoked amygdala responses

A number of recent papers have suggested that the amygdala plays a role in the brain's novelty detection circuit. In a recent study, we showed that this role may be specific to certain classes of biologically-relevant stimuli, such as human faces. The purpose of the present experiment was to determine whether other biologically-relevant stimuli also evoke novelty specific amygdala responses. To test this idea, we presented novel and repeated images of snakes and flowers while measuring BOLD. Surprisingly, we found that novel images of snakes and flowers evoke more amygdala activity than repeated images of snakes and flowers. Our results further confirm the robustness of the novelty evoked amygdala responses, even when compared with effects more traditionally associated with the amygdala. In addition, our results suggest that threatening stimuli may prime the amygdala to respond to other types of stimuli as well.