Hippocampus and amygdala volumes in a random community-based sample of 60-64 year olds and their relationship to cognition

The effect of estrogen therapy on cerebral metabolism in diabetic female rats

The impact of estrogen on brain function, especially in individuals with diabetes, remains uncertain. This study aims to compare cerebral glucose metabolism levels in intact rats, ovariectomized (OVX) rats, and 17β-estradiol (E2)-treated OVX diabetic female rats. Sixteen rats were administered a single intraperitoneal injection of 70 mg/kg streptozotocin (STZ) to induce diabetes (intact, n = 6; OVX, n = 6; OVX+E2-treated, n = 4). Additionally, 18 rats received an equivalent solvent dose via intraperitoneal injection (intact, n = 6; OVX, n = 6; OVX+E2-treated, n = 6). After 4 weeks of STZ or solvent administration, positron emission tomography scans with 18F-fluorodeoxyglucose (18F-FDG) injection were employed to assess cerebral glucose metabolism. The diabetic rats exhibited substantial reductions in 18F-FDG uptake across all brain regions (all P < 0.01), in contrast to the control rats. Moreover, intact and OVX + E2-treated diabetic female rats displayed more pronounced decreases in cerebral glucose metabolism in the amygdala and hippocampus compared to OVX diabetic female rats (P < 0.05). These findings suggest that diabetes creates an environment wherein estrogen exacerbates neuropathology and intensifies neuronal activity.

Coupling Between Hippocampal Parenchymal Fraction and Cortical Grey Matter Atrophy at Different Stages of Cognitive Decline

BACKGROUND

Hippocampal atrophy is a significant brain marker of pathology in Alzheimer's disease (AD). The hippocampal parenchymal fraction (HPF) was recently developed to better assess the hippocampal volumetric integrity, and it has been shown to be a sensitive measure of hippocampal atrophy in AD.

OBJECTIVE

To investigate the clinical relevance of hippocampal volumetric integrity as measured by the HPF and the coupling between the HPF and brain atrophy during AD progression.

METHODS

We included data from 143 cognitively normal (CN), 101 mild cognitive impairment (MCI), and 125 AD participants. We examined group differences in the HPF, associations between HPF and cognitive ability, and coupling between the HPF and cortical grey matter volume in the CN, MCI, and AD groups.

RESULTS

We observed progressive decreases in HPF from CN to MCI and from MCI to AD, and increases in the asymmetry of HPF, with the lowest asymmetry index (AI) in the CN group and the highest AI in the AD group. There was a significant association between HPF and cognitive ability across participants. The coupling between HPF and cortical regions was observed in bilateral hippocampus, parahippocampal gyrus, temporal, frontal, and occipital regions, thalamus, and amygdala in CN, MCI, and AD groups, with a greater involvement of temporal, occipital, frontal, and subcortical regions in MCI and AD patients, especially in AD patients.

CONCLUSION

This study provides novel evidence for the neuroanatomical basis of cognitive decline and brain atrophy during AD progression, which may have important clinical implications for the prognosis of AD.

Interpretation for Individual Brain Age Prediction Based on Gray Matter Volume

The relationship between age and the central nervous system (CNS) in humans has been a classical issue that has aroused extensive attention. Especially for individuals, it is of far greater importance to clarify the mechanisms between CNS and age. The primary goal of existing methods is to use MR images to derive high-accuracy predictions for age or degenerative diseases. However, the associated mechanisms between the images and the age have rarely been investigated. In this paper, we address the correlation between gray matter volume (GMV) and age, both in terms of gray matter themselves and their interaction network, using interpretable machine learning models for individuals. Our goal is not only to predict age accurately but more importantly, to explore the relationship between GMV and age. In addition to targeting each individual, we also investigate the dynamic properties of gray matter and their interaction network with individual age. The results show that the mean absolute error (MAE) of age prediction is 7.95 years. More notably, specific locations of gray matter and their interactions play different roles in age, and these roles change dynamically with age. The proposed method is a data-driven approach, which provides a new way to study aging mechanisms and even to diagnose degenerative brain diseases.

Profile of Hippocampal Volume of Adults in North Sumatera

BACKGROUND: Hippocampus is a brain region that includes in the limbic lobe. It is formed by two groups of neurons that look such as letter C, which were facing each other – dentate gyrus and Ammon’s horn and played an essential role in the development of memory. AIM: The objective of this study is to find the volume of the right and left hippocampal volume and the measurement of the total volume. To the best of our knowledge, this is the first study in Indonesia that measures the hippocampal volume of healthy adults. METHODS: We collected 54 subjects of healthy adults in Medan Indonesia, with the inclusion criteria: Age 15–40 years, cooperative and willing to be interviewed, and did not have a family history of mental disorders. Exclusion criteria for the control group were excluded from the study: Having a history of previous mental disorders and a general medical condition that affected brain structure, and obesity. We used MINI ICD-10 structured clinical interview to rule out the mental disorders. Hippocampal measurement was done by manual segmentation using AnalyzePro software that was developed by Mayo Clinic and followed the protocol of manual segmentation of hippocampal measurement from the Alzheimer’s Disease Neuroimaging Initiative: Magnetic resonance imaging methods. RESULTS: We found that the total hippocampal volume was 3979.77 ± 678.51 mm3. COCLUSION: Our findings of hippocampal volume were smaller than other Asian people. Few conditions had been thought related to it, that is, chronic stress exposure inducing prolonged hypothalamic-pituitary-adrenal axis activation that leads to loss of hippocampal neurons and neural level conditions resulting from gene-environment interaction. This smaller hippocampal volume can also predict verbal memory function in the future.

Longitudinal Effects of Physical Activity Change on Hippocampal Volumes over up to 12 Years in Middle and Older Age Community-Dwelling Individuals

The objectives of this study were to investigate the long-term associations between changes in physical activity levels and hippocampal volumes over time, while considering the influence of age, sex, and APOE-ε4 genotype. We investigated the effects of change in physical activity on hippocampal volumes in 411 middle age (mean age = 47.2 years) and 375 older age (mean age = 63.1 years) adults followed up to 12 years. An annual volume decrease was observed in the left (middle age: 0.46%; older age: 0.51%) but not in the right hippocampus. Each additional 10 metabolic equivalents (METs, ~2 h of moderate exercise) increase in weekly physical activity was associated with 0.33% larger hippocampal volume in middle age (equivalent to ~1 year of typical aging). In older age, each additional MET was associated with 0.05% larger hippocampal volume; however, the effects declined with time by 0.005% per year. For older age APOE-ε4 carriers, each additional MET was associated with a 0.10% increase in hippocampal volume. No sex effects of physical activity change were found. Increasing physical activity has long-term positive effects on hippocampal volumes and appears especially beneficial for older APOE-ε4 carriers. To optimize healthy brain aging, physical activity programs should focus on creating long-term exercise habits.

A Mixed-Effects Model of Associations between Interleukin-6 and Hippocampal Volume

Previous studies report hippocampal volume loss can help predict conversion from normative aging to mild cognitive impairment (MCI) to dementia. Additionally, a growing literature indicates that stress-related allostatic load may increase disease vulnerability. The current study examined the relationship between stress related cytokines (i.e., interleukin-6 - IL-6), cognition as measured by Mini Mental Status scores (MMSE), and hippocampal volume. Mixed-models were employed to examine both within (across time) and between subjects effects of IL-6 and hippocampal volume on MMSE score among 566 participants from the Alzheimer's Disease Neuroimaging Initiative (ADNI). The within subjects analysis found left hippocampal volume significantly (p= .009) predicted MMSE score. Between subjects analysis found the effect of IL-6 on MMSE was moderated by right hippocampal volume (p = .001). These results replicate previous findings and also extend prior work demonstrating stress-related cytokines may play a role in Alzheimer's disease (AD) progression.

Effect of Gender on Development of Hippocampal Subregions From Childhood to Adulthood

The hippocampus is known to be comprised of several subfields, but the developmental trajectories of these subfields are under debate. In this study, we analyzed magnetic resonance imaging (MRI) data from a cross-sectional sample (198 healthy Chinese) using an automated segmentation tool to delineate the development of the hippocampal subregions from 6 to 26 years of age. We also examined whether gender and hemispheric differences influence the development of these subregions. For the whole hippocampus, the trajectory of development was observed to be an inverse-u. A significant increase in volume with age was found for most of the subregions, except for the L/R-parasubiculum, L/R-fimbria, and L-HATA. Gender-related differences were also found in the development of most subregions, especially for the hippocampal tail, CA1, molecular layer HP, GC-DG, CA3, and CA4, which showed a consistent increase in females and an early increase followed by a decrease in males. A comparison of the average volumes showed that the right whole hippocampus was significantly larger, along with the R-presubiculum, R-hippocampal-fissure, L/R-CA1, and L/R-molecular layer HP in males in comparison to females. Additionally, the average volume of the right hemisphere was shown to be significantly larger for the hippocampal tail, CA1, molecular layer HP, GC-DG, CA3, and CA4. However, for the presubiculum, parasubiculum, and fimbria, the left side was shown to be larger. In conclusion, the hippocampal subregions appear to develop in various ways from childhood to adulthood, with both gender and hemispheric differences affecting their development.

Longitudinal trajectories of hippocampal volume in middle to older age community dwelling individuals

Understanding heterogeneity in brain aging trajectories is important to estimate the extent to which aging outcomes can be optimized. Although brain changes in late life are well-characterized, brain changes in middle age are not well understood. In this study, we investigated hippocampal change in a generally healthy community-living population of middle (n = 421, mean age 47.2 years) and older age (n = 411, mean age 63.0 years) individuals, over a follow-up of up to 12 years. Manually traced hippocampal volumes were analyzed using multilevel models and latent class analysis to investigate longitudinal aging trajectories and laterality and sex effects, and to identify subgroups that follow different aging trajectories. Hippocampal volumes decreased on average by 0.18%/year in middle age and 0.3%/year in older age. Men tended to experience steeper declines than women in middle age only. Three subgroups of individuals following different trajectories were identified in middle age and 2 in older age. Contrary to expectations, the subgroup containing two-thirds of older age participants maintained stable hippocampal volumes across the follow-up.

Effects of sex, age, and apolipoprotein E genotype on hippocampal parenchymal fraction in cognitively normal older adults

Early detection of Alzheimer's disease (AD) is important for timely interventions and developing new treatments. Hippocampus atrophy is an early biomarker of AD. The hippocampal parenchymal fraction (HPF) is a promising measure of hippocampal structural integrity computed from structural MRI. It is important to characterize the dependence of HPF on covariates such as age and sex in the normal population to enhance its utility as a disease biomarker. We measured the HPF in 4239 structural MRI scans from 340 cognitively normal (CN) subjects aged 59-89 years from the AD Neuroimaging Initiative database, and studied its dependence on age, sex, apolipoprotein E (APOE) genotype, brain hemisphere, intracranial volume (ICV), and education using a linear mixed-effects model. In this CN cohort, HPF was inversely associated with ICV; was greater on the right hemisphere compared to left in both sexes with the degree of right > left asymmetry being slightly more pronounced in men; declined quadratically with age and faster in APOE ϵ4 carriers compared to non-carriers; and was significantly associated with cognitive ability. Consideration of HPF as an AD biomarker should be in conjunction with other subject attributes that are shown in this research to influence HPF levels in CN older individuals.

Sex differences in gray matter volume: how many and how large are they really?

Background

Studies assessing volumetric sex differences have provided contradictory results. Total intracranial volume (TIV) is a major confounding factor when estimating local volumes of interest (VOIs). We investigated how the number, size, and direction of sex differences in gray matter volume (GMv) vary depending on how TIV variation is statistically handled.

Methods

Sex differences in the GMv of 116 VOIs were assessed in 356 participants (171 females) without correcting for TIV variation or after adjusting the data with 5 different methods (VBM8 non-linear-only modulation, proportions, power-corrected-proportions, covariation, and the residuals method). The outcomes obtained with these procedures were compared to each other and to those obtained in three criterial subsamples, one comparing female-male pairs matched on their TIV and two others comparing groups of either females or males with large/small TIVs. Linear regression was used to quantify TIV effects on raw GMv and the efficacy of each method in controlling for them.

Results

Males had larger raw GMv than females in all brain areas, but these differences were driven by direct TIV-VOIs relationships and more closely resembled the differences observed between individuals with large/small TIVs of sex-specific subsamples than the sex differences observed in the TIV-matched subsample. All TIV-adjustment methods reduced the number of sex differences but their results were very different. The VBM8- and the proportions-adjustment methods inverted TIV-VOIs relationships and resulted in larger adjusted volumes in females, promoting sex differences largely attributable to TIV variation and very distinct from those observed in the TIV-matched subsample. The other three methods provided results unrelated to TIV and very similar to those of the TIV-matched subsample. In these datasets, sex differences were bidirectional and achieved satisfactory replication rates in 19 VOIs, but they were “small” (d < ∣0.38∣) and most of them faded away after correcting for multiple comparisons.

Conclusions

There is not just one answer to the question of how many and how large the sex differences in GMv are, but not all the possible answers are equally valid. When TIV effects are ruled out using appropriate adjustment methods, few sex differences (if any) remain statistically significant, and their size is quite reduced.

Electronic supplementary material

The online version of this article (10.1186/s13293-019-0245-7) contains supplementary material, which is available to authorized users.

Sexual Dimorphism and Hemispheric Asymmetry of Hippocampal Volumetric Integrity in Normal Aging and Alzheimer Disease

BACKGROUND AND PURPOSE

Asymmetric atrophy of the hippocampus is an important clinical finding in normal aging and Alzheimer disease. In this study, we investigate the associations between the magnitude and asymmetry of hippocampal volumetric integrity and age, sex, and dementia severity.

MATERIALS AND METHODS

We have recently developed a rapid fully automatic algorithm to measure the hippocampal parenchymal fraction, an index of hippocampal volumetric integrity on structural MR imaging of the brain. We applied this algorithm to measure the hippocampal parenchymal fraction bilaterally on 775 MR imaging volumes scanned from 198 volunteers in a publicly available data base. All subjects were right-handed and older than 60 years of age. Subjects were categorized as cognitively healthy (n = 98), with mild cognitive impairment (n = 70), or with mild/moderate Alzheimer disease (n = 30). We used linear mixed-effects models to analyze the hippocampal parenchymal fraction and its asymmetry with respect to age, sex, dementia severity, and intracranial volume.

RESULTS

After controlling for age, sex, and intracranial volume, we found that the magnitude of the hippocampal parenchymal fraction decreased and its asymmetry increased significantly with dementia severity. Also, hippocampal parenchymal fraction asymmetry was significantly higher in men after controlling for all other variables, but there was no sex effect on hippocampal parenchymal fraction magnitude. The magnitude of the hippocampal parenchymal fraction decreased and its asymmetry increased significantly with age in subjects who were cognitively healthy, but associations with age were different in nature in the mild cognitive impairment and Alzheimer disease groups.

CONCLUSIONS

Hippocampal atrophy progresses asymmetrically with age in cognitively healthy subjects. Hippocampal parenchymal fraction asymmetry is significantly higher in men than women and in mild cognitive impairment/Alzheimer disease relative to cognitively healthy individuals.

Gender Differences in Cognitive Test Performance in Adults With Heart Failure

BACKGROUND

Cognitive deficits are found in up to 73% of persons with heart failure (HF) and are associated with increased mortality and other poor clinical outcomes. It is known that women have better memory test performance than men do in healthy samples, but gender differences in cognitive performance in the context of HF are not well understood and may have important clinical implications.

OBJECTIVE

The objective of this study was to examine possible gender differences in cognitive function in a sample of individuals with HF (98.9% New York Heart Association class II and III).

METHODS

A total of 183 adults with HF (116 men and 67 women) completed a neuropsychological test battery as part of a larger project. Measures were chosen to assess functioning in attention/executive function and memory.

RESULTS

After controlling for demographic and medical factors, multivariate analysis of covariance revealed that men and women differed on memory test performance (λ = 0.90, F4, 169 = 4.76, P = .001). Post hoc comparisons revealed that women performed better on California Verbal Learning Test Learning, Short Recall, and Delayed Recall. No differences emerged on tests of attention/executive function (λ = 0.97, F5, 168 = 0.96, P = .44).

CONCLUSIONS

In this sample of persons with HF, men exhibited poorer performance on memory measures than women did. Future studies are needed to determine the underlying mechanisms for this pattern and its possible influence on daily function.

Gender differences of neuropsychological profiles in cognitively normal older people without amyloid pathology

OBJECTIVE

To investigate the impact of sex on cognition among cognitively normal older people without amyloid pathology.

METHODS

The study sample consisted of 83 males (mean age 74years, ranging from 65 to 88years) and 111 females (mean age 72years, ranging from 65 to 89years) who were cognitively normal without amyloid pathology confirmed by Pittsburgh compound B PET scan. We examined the sex discrepancies in cognition using a comprehensive neuropsychological battery.

RESULTS

Our data showed significantly greater advantage for women than men on the tasks of verbal memory and category fluency while better performance of naming in men than women when age, education and depressive symptoms were considered.

CONCLUSION

These findings highlight the importance of considering sex differences in the interpretation of cognitive data which contribute to clinical diagnosis of neurodegenerative disorders, such as Alzheimer's disease.

Meta-analysis reveals a lack of sexual dimorphism in human amygdala volume

The amygdala plays a key role in many affective behaviors and psychiatric disorders that differ between men and women. To test whether human amygdala volume (AV) differs reliably between the sexes, we performed a systematic review and meta-analysis of AVs reported in MRI studies of age-matched healthy male and female groups. Using four search strategies, we identified 46 total studies (58 matched samples) from which we extracted effect sizes for the sex difference in AV. All data were converted to Hedges g values and pooled effect sizes were calculated using a random-effects model. Each dataset was further meta-regressed against study year and average participant age. We found that uncorrected amygdala volume is about 10% larger in males, with pooled sex difference effect sizes of g=0.581 for right amygdala (κ=28, n=2022), 0.666 for left amygdala (κ=28, n=2006), and 0.876 for bilateral amygdala (κ=16, n=1585) volumes (all p values < 0.001). However, this difference is comparable to the sex differences in intracranial volume (ICV; g=1.186, p<.001, 11.9% larger in males, κ=11) and total brain volume (TBV; g=1.278, p<0.001, 11.5% larger in males, κ=15) reported in subsets of the same studies, suggesting the sex difference in AV is a product of larger brain size in males. Among studies reporting AVs normalized for ICV or TBV, sex difference effect sizes were small and not statistically significant: g=0.171 for the right amygdala (p=0.206, κ=13, n=1560); 0.233 for the left amygdala (p=0.092, κ=12, n=1512); and 0.257 for bilateral volume (p=0.131, κ=5, n=1629). These values correspond to less than 0.1% larger corrected right AV and 2.5% larger corrected left AV in males compared to females. In summary, AV is not selectively enhanced in human males, as often claimed. Although we cannot rule out subtle male-female group differences, it is not accurate to refer to the human amygdala as "sexually dimorphic."

White matter correlates of episodic memory encoding and retrieval in schizophrenia

Episodic memory (EM) impairments in schizophrenia (SZ) are predictive of functional outcome and are a potential endophenotype of the disorder. The current study investigated the neuroanatomical correlates of EM encoding and retrieval in SZ with structural magnetic resonance and diffusion tensor imaging (DTI) measures in 22 patients with SZ and 22 age- and gender-matched healthy controls. Tract-based Spatial Statistics (TBSS) was used to investigate microstructural alterations in white matter (WM), while FreeSurfer surface-based analysis was used to determine abnormalities in grey matter (GM) and WM volumetrics and cortical thickness. Compared to controls, patients demonstrated GM deficits in temporal and parietal regions and lower fractional anisotropy (FA) of WM in diffuse brain regions. Patients also demonstrated reduced functioning in both encoding and retention of auditory-verbal EM. Among patients but not controls, EM encoding correlated with WM volume in the orbitofrontal cortex and increased radial diffusivity in the fornix, whereas EM retrieval correlated with WM volume in posterior parietal cortex. These findings suggest a differential role for frontal and parietal WM in EM encoding and retrieval processes, while myelin integrity of the fornix may play a specific role in mediating EM encoding processes in SZ.

Western diet is associated with a smaller hippocampus: a longitudinal investigation

BACKGROUND

Recent meta-analyses confirm a relationship between diet quality and both depression and cognitive health in adults. While the biological pathways that underpin these relationships are likely multitudinous, extensive evidence from animal studies points to the involvement of the hippocampus. The aim of this study was to examine the association between dietary patterns and hippocampal volume in humans, and to assess whether diet was associated with differential rates of hippocampal atrophy over time.

METHODS

Data were drawn from the Personality and Total Health Through Life Study and focused on a subsample of the cohort (n = 255) who were aged 60-64 years at baseline in 2001, completed a food frequency questionnaire, and underwent two magnetic resonance imaging scans approximately 4 years apart. Longitudinal generalized estimating equation linear regression models were used to assess the association between dietary factors and left and right hippocampal volumes over time.

RESULTS

Every one standard deviation increase in healthy "prudent" dietary pattern was associated with a 45.7 mm(3) (standard error 22.9 mm(3)) larger left hippocampal volume, while higher consumption of an unhealthy "Western" dietary pattern was (independently) associated with a 52.6 mm(3) (SE 26.6 mm(3)) smaller left hippocampal volume. These relationships were independent of covariates including age, gender, education, labour-force status, depressive symptoms and medication, physical activity, smoking, hypertension and diabetes. While hippocampal volume declined over time, there was no evidence that dietary patterns influenced this decline. No relationships were observed between dietary patterns and right hippocampal volume.

CONCLUSIONS

Lower intakes of nutrient-dense foods and higher intakes of unhealthy foods are each independently associated with smaller left hippocampal volume. To our knowledge, this is the first human study to demonstrate associations between diet and hippocampal volume concordant with data previously observed in animal models.

Quantitative Measurements in the Human Hippocampus and Related Areas: Correspondence between Ex-Vivo MRI and Histological Preparations

The decrease of volume estimates in different structures of the medial temporal lobe related to memory correlate with the decline of cognitive functions in neurodegenerative diseases. This study presents data on the association between MRI quantitative parameters of medial temporal lobe structures and their quantitative estimate in microscopic examination. Twelve control cases had ex-vivo MRI, and thereafter, the temporal lobe of both hemispheres was sectioned from the pole as far as the level of the splenium of the corpus callosum. Nissl stain was used to establish anatomical boundaries between structures in the medial temporal lobe. The study included morphometrical and stereological estimates of the amygdaloid complex, hippocampus, and temporal horn of the lateral ventricle, as well as different regions of grey and white matter in the temporal lobe. Data showed a close association between morphometric MRI images values and those based on the histological determination of boundaries. Only values in perimeter and circularity of the piamater were different. This correspondence is also revealed by the stereological study, although irregular compartments resulted in a lesser agreement. Neither age (< 65 yr and > 65 yr) nor hemisphere had any effect. Our results indicate that ex-vivo MRI is highly associated with quantitative information gathered by histological examination, and these data could be used as structural MRI biomarker in neurodegenerative diseases.

Hippocampal atrophy is associated with subjective memory decline: The PATH Through Life study

OBJECTIVE

To investigate whether subjective memory decline (SMD) in cognitively healthy individuals is associated with hippocampal atrophy.

METHODS

Multiple regression analyses assessing the relationship between hippocampal atrophy over 4 years and SMD at baseline and follow-up in 305 cognitively healthy individuals aged 60-64 years free from dementia, mild cognitive impairment, and other neurological disorders.

RESULTS

SMD at baseline was not a significant predictor of hippocampal atrophy. However, SMD at follow-up was associated with greater hippocampal atrophy. Associations were reduced but remained significant after controlling for anxiety and depression symptomatology.

CONCLUSION

Hippocampal atrophy was associated with incident/persisting SMD and this association was not, or only partly, explained by anxiety and depression symptomatology. These results are consistent with a biological origin to subjective memory decline. SMD should be included in screening and neuropsychological batteries.

Executive functions in men and postmenopausal women

INTRODUCTION

This study was designed to assess sex differences in older adults (55-65 years old) in executive functions and to examine the influence of hormone therapy (HT) in postmenopausal women.

METHOD

We have assessed task performance in memory, visuospatial, and executive functions in 29 women using HT, 29 women who never used HT, and 30 men.

RESULTS

Men outperformed never users in task switching and updating. HT users outperformed never users in updating. HT users outperformed never users and men in visual divided attention.

DISCUSSION

The present study support previous findings that sex and HT impact cognition and bring new insights on sex and HT-related differences in executive functions.

Intracranial volume estimated with commonly used methods could introduce bias in studies including brain volume measurements

In brain volumetric studies, intracranial volume (ICV) is often used as an estimate of pre-morbid brain size as well as to compensate for inter-subject variations in head size. However, if the estimated ICV is biased by for example gender or atrophy, it could introduce errors in study results. To evaluate how two commonly used methods for ICV estimation perform, computer assisted reference segmentations were created and evaluated. Segmentations were created for 399 MRI volumes from 75-year-old subjects, with 53 of these subjects having an additional scan and segmentation created at age 80. ICV estimates from Statistical Parametric Mapping (SPM, version 8) and Freesurfer (FS, version 5.1.0) were compared to the reference segmentations, and bias related to skull size (approximated with the segmentation measure), gender or atrophy were tested for. The possible ICV related effect on associations between normalized hippocampal volume and factors gender, education and cognition was evaluated by normalizing hippocampal volume with different ICV measures. Excellent agreement was seen for inter- (r=0.999) and intra- (r=0.999) operator reference segmentations. Both SPM and FS overestimated ICV. SPM showed bias associated with gender and atrophy while FS showed bias dependent on skull size. All methods showed good correlation between time points in the longitudinal data (reference: 0.998, SPM: 0.962, FS: 0.995). Hippocampal volume showed different associations with cognition and gender depending on which ICV measure was used for hippocampal volume normalization. These results show that the choice of method used for ICV estimation can bias results in studies including brain volume measurements.

Hippocampal and amygdala volumes in an older bipolar disorder sample

BACKGROUND

Brain volumetric magnetic resonance imaging (MRI) studies of adult bipolar disorder samples, compared with healthy controls, have reported conflicting results in hippocampal and amygdala volumes. Among these, few have studied older bipolar samples, which would allow for examination of the effects of greater duration in mood episodes on brain volumes. The aim of this study was to compare hippocampal and amygdala volumes in older bipolar patients with controls.

METHODS

High-resolution MRI scans were used to determine hippocampal and amygdala volumes that were manually traced using established protocols in 18 euthymic patients with DSM-IV bipolar I disorder (mean age 57 years) and 21 healthy controls (mean age 61 years). Analysis of covariance (ANCOVA) was used to explore group differences while controlling for intracranial volume (ICV), age, sex, and years of education.

RESULTS

While gray matter, white matter, and cerebrospinal fluid volumes did not differ between the groups, bipolar disorder patients had smaller ICV (t = 2.54, p = 0.015). After correcting for ICV, the bipolar group had smaller hippocampal (left hippocampus F = 13.944, p = 0.001; right hippocampus F = 10.976, p = 0.002; total hippocampus F = 13.566; p = 0.001) and right amygdala (F = 13.317, p = 0.001) volumes. Total hippocampal volume was negatively associated with the duration of depressive (r = -0.636; p = 0.035) and manic (r = -0.659; p = 0.027) episodes, but not lithium use. Amygdala volumes were not associated with the duration of mood episodes.

CONCLUSIONS

Older bipolar disorder patients had smaller hippocampal and amygdala volumes. That smaller hippocampal volume was associated with the duration of mood episodes may suggest a neuroprogressive course related to the severity of the disorder.

Toward a better understanding of the savant brain

OBJECTIVE

The objectives of this study are to investigate the neuroanatomy, regional brain connectivity, and neurochemistry of a prodigious artistic savant; to place these findings within the context of existing neuroimaging literature of savant syndrome; and to discuss the utility of newer imaging modalities to extend our current understanding of mechanisms underlying savant skills.

METHODS

High-resolution magnetic resonance (MR) imaging, J-resolved MR spectroscopy, and diffusion tensor imaging data were acquired during a single scanning session for a 63-year-old male autistic savant with prodigious artistic skills. Regional and compartmental brain volumes, N-acetyl aspartate, choline, creatine, glutamate and γ-aminobutyric acid concentrations, fractional anisotropy values, and white matter bundle volumes as well as axial, radial, and mean diffusivities were calculated.

RESULTS

No gross anatomical differences were observed. By morphological assessment, cerebral volume (1362 mL) was larger than normative literature values for adult males. The corpus callosum was intact and did not exhibit abnormal structural features. The right cerebral hemisphere was 1.9% larger than the left hemisphere; the right amygdala and right caudate nuclei were 24% and 9.9% larger, respectively, compared with the left side. In contrast, the putamen was 8.3% larger on the left side. Fractional anisotropy was increased on the right side as compared with the left for 4 of the 5 bilateral regions studied (the amygdala, caudate, frontal lobe, and hippocampus). Fiber tract bundle volumes were larger on the right side for the amygdala, hippocampus, frontal lobe, and occipital lobe. Both the left and the right hippocampi had substantially increased axial and mean diffusivities as compared with those of a comparison sample of nonsavant adult males. The corpus callosum and left amygdala also exhibited high axial, radial, and mean diffusivities. MR spectroscopy revealed markedly decreased γ-aminobutyric acid and glutamate in the parietal lobe.

CONCLUSIONS

Although examination of brain gross morphometry demonstrated no clinically remarkable abnormalities, utilization of conventional as well as newer MR imaging technologies revealed several atypical structural and chemical features that may be involved in the special skills of this prodigious savant. The multimodal imaging approach presented in this study is suitable for the evaluation of larger samples of savants with a diverse range of talents to investigate common brain features that may underlie the exceptional cognitive capabilities characteristic of savant syndrome. Given the high co-occurrence of the two syndromes, elucidating the underlying neurophysiologic basis of savant syndrome may also lead to a better understanding of autism spectrum disorder.

Sex differences in cognition in healthy elderly individuals

Sex differences in patterns of cognitive test performance have been attributed to factors, such as sex hormones or sexual dimorphisms in brain structure, that change with normal aging. The current study examined sex differences in patterns of cognitive test performance in healthy elderly individuals. Cognitive test scores of 957 men and women (age 67-89), matched for overall level of cognitive test performance, age, education, and depression scale score, were compared. Men and women were indistinguishable on tests of auditory divided attention, category fluency, and executive functioning. In contrast, women performed better than men on tests of psychomotor speed and verbal learning and memory, whereas men outperformed women on tests of visuoconstruction and visual perception. Our finding that the pattern of sex differences in cognition observed in young adults is observed in old age has implications for future studies of both healthy elderly individuals and of those with cognitive disorders.

Mixed handedness is associated with greater age-related decline in volumes of the hippocampus and amygdala: the PATH through life study

Handedness has been found to be associated with structural and functional cerebral differences. Left handedness and mixed handedness also appear to be associated with an elevated risk of some developmental and immunological disorders that may contribute to pathological processes developing in ageing. Inconsistent reports show that left handedness may be more prevalent in early-onset as well as late-onset Alzheimer's disease, but might also be associated with slower decline. Such inconsistencies may be due to handedness being usually modeled as a binary construct while substantial evidence suggests it to be a continuous trait. The aim of this study was to investigate the relationship between brain structures known to be implicated in pathological ageing and strength and direction of handedness. The association between handedness and hippocampal and amygdalar atrophy was investigated in 327 cognitively healthy older individuals. Handedness was measured with the Edinburgh Inventory. Two measures were computed from this index, one reflecting the direction (left = 0/right = 1) and the other the degree of handedness (ranging from 0 to 1). Hippocampal and amygdalar volumes were manually traced on scans acquired 4 years apart. Regression analyses were used to assess the relationship between strength and direction of handedness and incident hippocampal and amygdalar atrophy. Analyses showed that strength but not direction of handedness was a significant predictor of hippocampal (Left: beta = 0.118, P = 0.013; Right: beta = 0.116, P = 0.010) and amygdalar (Right: beta = 0.105, P = 0.040) atrophy. The present findings suggest that mixed but not left handedness is associated with greater hippocampal and amygdalar atrophy. This effect may be due to genetic, environmental, or behavioural differences that will need further investigation in future studies.

Hippocampus, amygdala and global brain changes 10 years after childhood traumatic brain injury

Traumatic brain injury (TBI) in children results in damage to the developing brain, particularly in severely injured individuals. Little is known, however, of the long-term structural aspects of the brain following childhood TBI. This study investigated the integrity of the brain 10 years post-TBI using magnetic resonance imaging volumetrics in a sample of 49 participants with mild, moderate and severe TBI, evaluated against a normative sample of 20 individuals from a pediatric database with comparable age and gender distribution. Structural integrity was investigated in gray and white matter, and by manually segmenting two regions of interest (hippocampus, amygdala), potentially vulnerable to the effects of childhood TBI. The results indicate that more severe injuries caused a reduction in gray and white brain matter, while all TBI severity levels resulted in increased volumes of cerebrospinal fluid and smaller hippocampal volumes. In addition, enlarged amygdala volumes were detected in severely injured patients compared to their mild and moderate counterparts, suggesting that childhood TBI may disrupt the development of certain brain regions through diffuse pathological changes. The findings highlight the lasting impact of childhood TBI on the brain and the importance of monitoring brain structure in the long-term after early injury.

Hippocampal sulcal cavities: prevalence, risk factors and relationship to memory impairment

While hippocampal volumes have been extensively examined in neuropsychiatric disorders and ageing, small areas of signal variation within the hippocampus commonly observed on MRI, described as hippocampal sulcal cavities (HSCs), have received less attention. We review the published literature on HSCs to examine their prevalence, putative aetiological factors such as hypertension, and possible cognitive correlates. HSCs were reported in 77% (66% weighted mean) of patients with memory disorders and 48% (47% weighted mean) of controls, and the prevalence increased with age in healthy subjects (r=0.64, p=0.047). A number of studies reported hypertension as a risk factor, and related their presence to poorer memory function. Further work is needed to fully understand the clinical significance of these lesions.

Hippocampal volumetrics in treatment-resistant depression and schizophrenia: the devil's in de-tail

Studies of patients with major depressive disorder (MDD) and schizophrenia (SCH) have revealed reduced hippocampal volumes, but findings have been inconsistent due to sample and measurement differences. The current study sought to measure this structure in a large sample of MDD, SCH, and healthy subjects, using a strict measurement protocol, to elucidate morphological-specific volumetric differences. Patients with treatment-resistant MDD (N = 182) and treatment-resistant SCH with auditory-verbal hallucinations (N = 52), and healthy controls (N = 76) underwent psychiatric assessments and brain MRI. The findings indicate that (1) MDD and SCH patients have reduced total hippocampal volume which was marked in the tails (more so in patients with MDD), (2) region of interest estimation protocols and sample characteristics may help explain volumetric differences between previous SCH studies.

Enlargement of the hippocampal angle: a new index of Alzheimer disease

BACKGROUND

Imaging diagnosis of Alzheimer disease (AD), the leading cause of dementia, requires evaluation of the extent of hippocampal atrophy. Coronal magnetic resonance (MR) images of patients with AD often demonstrate outward rotation of the hippocampus that is altered from a long horizontal elliptical to a long vertical elliptical shape. Such rotation may be related to the disease process of AD.

PURPOSE AND METHODS

To determine whether hippocampal rotation is associated with AD, we investigated MR images from 11 patients with AD and 11 normal controls, measuring the hippocampal angle (HA) and the volume of the left hippocampus on coronal T(1)-weighted MR images. The HA is the angle between a horizontal line orthogonal to the falx cerebri and the uncal sulcus line between the deepest point of the uncal sulcus and the point nearest to the side of the ambient cistern in the uncal gyrus facing the uncal sulcus. The HA is measured on the most rostral slice in which the uncal sulcus can be identified and increases with hippocampal rotation.

RESULTS

We found correlation between the HA and standardized hippocampal volume in the AD group, but not in controls.

CONCLUSION

Hippocampal rotation is a new marker associated with the pathology of AD.

Small baseline volume of left hippocampus is associated with subsequent conversion of MCI into dementia: the Göteborg MCI study

BACKGROUND

Earlier studies have reported that hippocampal atrophy can to some extent predict which patients with mild cognitive impairment (MCI) will subsequently convert to dementia, and that converters have an enhanced rate of hippocampal volume loss.

OBJECTIVE

To further validate the hypothesis that hippocampal atrophy predicts conversion from MCI to dementia, to relate baseline hippocampal volume to different forms of dementia, and to investigate the role of hippocampal side differences and rate of volume loss over time.

PATIENTS

The subjects (N=68) include patients with MCI at baseline and progression to dementia at the two-year follow-up (N=21), stable MCI patients (N=21), and controls (N=26). Among the progressing patients, 13 were diagnosed as having AD.

METHODS

The Göteborg MCI study is a clinically based longitudinal study with biannual clinical assessments. Hippocampal volumetry was performed manually on the MRI investigations at baseline and at the two-year follow-up.

RESULTS

Hippocampal volumetry could predict conversion to dementia in both the AD and the non-AD subgroup of converters. Left hippocampal volume in particular discriminated between converting and stable MCI. Cut off points for individual discrimination were shown to be potentially useful. The converting MCI group had a significantly higher rate of hippocampal volume loss as compared to the stable MCI group.

CONCLUSIONS

In MCI patients, hippocampal volumetry at baseline gives prognostic information about possible development of AD and non-AD dementia. Contrary to earlier studies, we found that left hippocampal volume has the best predictive power. Reliable predictions appear to be possible in many individual cases.