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

Fetal Fornix-Hippocampus Complex and Hippocampus Height Measurements Between 18 and 24 Weeks of Gestation and the Effect of Maternal Iron Deficiency Anemia

PURPOSE

To construct nomograms for both sides of the fetal fornix-hippocampus complex (FHC) length and hippocampus height between 18 + 0 and 23 + 6 weeks of gestation using two-dimensional sonography. Additionally, we evaluated the effects of laterality, fetal sex, and maternal iron deficiency anemia on these measurements.

METHODS

This was a prospective cross-sectional study of 223 singleton pregnancies between 18 + 0 and 23 + 6 weeks of gestation. The FHC length and hippocampus height were measured on both sides in the parasagittal cranial plane of the fetus by 2D ultrasonography. Measurements from 30 women with iron deficiency anemia, out of 223 patients, were compared to those of normal controls.

RESULTS

Nomograms for FHC length and hippocampus height were constructed, showing a strong correlation with gestational age. No significant differences were found between the right and left side FHC lengths or hippocampus heights (p > 0.05), nor between male and female fetuses (p > 0.05). The FHC lengths (p > 0.05) and hippocampus heights (p > 0.05) of fetuses in anemic and non-anemic pregnancies also showed no significant differences.

CONCLUSION

2D ultrasound morphology of the fetal hippocampus and fornix during the second trimester is not significantly different between pregnancies with iron deficiency anemia and nonanemic women.

Morphological characterization of the hippocampus: a first database in Ecuador

Introduction

The hippocampal volume is a well-known biomarker to detect and diagnose neurological, psychiatric, and psychological diseases. However, other morphological descriptors are not analyzed. Furthermore, not available databases, or studies, were found with information related to the hippocampal morphology from Latin-American patients living in the Andean highlands.

Methods

The hippocampus is manually segmented by two medical imaging specialists on normal brain magnetic resonance images. Then, its morphological qualitative and quantitative descriptors (volume, sphericity, roundness, diameter, volume-surface ratio, and aspect ratio) are computed via 3D digital level-set-based mathematical representation. Furthermore, other morphological descriptors and their possible correlation with the hippocampal volume is analyzed.

Results

We introduce a first database with the hippocampus' morphological characterization of 63 patients from Quito, Ecuador, male and female, aged between 18 and 95 years old.

Discussion

This study provides new research opportunities to neurologists, psychologists, and psychiatrists, to further understand the hippocampal morphology of Andean and Latin American patients.

Hippocampal subfield plasticity is associated with improved spatial memory

Physical exercise studies are generally underrepresented in young adulthood. Seventeen subjects were randomized into an intervention group (24.2 ± 3.9 years; 3 trainings/week) and 10 subjects into a passive control group (23.7 ± 4.2 years), over a duration of 6 months. Every two months, performance diagnostics, computerized spatial memory tests, and 3 Tesla magnetic resonance imaging were conducted. Here we find that the intervention group, compared to controls, showed increased cardiorespiratory fitness, spatial memory performance and subregional hippocampal volumes over time. Time-by-condition interactions occurred in right cornu ammonis 4 body and (trend only) dentate gyrus, left hippocampal tail and left subiculum. Increases in spatial memory performance correlated with hippocampal body volume changes and, subregionally, with left subicular volume changes. In conclusion, findings support earlier reports of exercise-induced subregional hippocampal volume changes. Such exercise-related plasticity may not only be of interest for young adults with clinical disorders of hippocampal function, but also for sedentary normal cohorts.

Age-related differences in hippocampal subfield volumes across the human lifespan: A meta-analysis

The human hippocampus (Hc) is critical for memory function across the lifespan. It is comprised of cytoarchitectonically distinct subfields: dentate gyrus (DG), cornu ammonis sectors (CA) 1-4, and subiculum, each of which may be differentially susceptible to neurodevelopmental and neurodegenerative mechanisms. Identifying age-related differences in Hc subfield volumes can provide insights into neural mechanisms of memory function across the lifespan. Limited evidence suggests that DG and CA3 volumes differ across development while other regions remain relatively stable, and studies of adulthood implicate a downward trend in all subfield volumes with prominent age effects on CA1. Due to differences in methods and limited sampling for any single study, the magnitude of age effects on Hc subfield volumes and their probable lifespan trajectories remain unclear. Here, we conducted a meta-analysis on cross-sectional studies (n = 48,278 participants, ages = 4-94 years) to examine the association between age and Hc subfield volumes in development (n = 11 studies), adulthood (n = 30 studies), and a combined lifespan sample (n = 41 studies) while adjusting estimates for sample sizes. In development, age was positively associated with DG and CA3-4 volumes, whereas in adulthood a negative association was observed with all subfield volumes. Notably, the observed age effects were not different across subfield volumes within each age group. All subfield volumes showed a nonlinear age pattern across the lifespan with DG and CA3-4 volumes showing a more distinct age trajectory as compared to the other subfields. Lastly, among all the study-level variables, only female percentage of the study sample moderated the age effect on CA1 volume: a higher female-to-male ratio in the study sample was linked to the greater negative association between age and CA1 volume. These results document that Hc subfield volumes differ as a function of age offering broader implications for constructing theoretical models of lifespan memory development.

Associations between alcohol use and sex-specific maturation of subcortical gray matter morphometry from adolescence to adulthood: Replication across two longitudinal samples

Subcortical brain morphometry matures across adolescence and young adulthood, a time when many youth engage in escalating levels of alcohol use. Initial cross-sectional studies have shown alcohol use is associated with altered subcortical morphometry. However, longitudinal evidence of sex-specific neuromaturation and associations with alcohol use remains limited. This project used generalized additive mixed models to examine sex-specific development of subcortical volumes and associations with recent alcohol use, using 7 longitudinal waves (n = 804, 51% female, ages 12-21 at baseline) from the National Consortium on Alcohol and Neurodevelopment in Adolescence (NCANDA). A second, independent, longitudinal dataset, with up to four waves of data (n = 467, 43% female, ages 10-18 at baseline), was used to assess replicability. Significant, replicable non-linear normative volumetric changes with age were evident in the caudate, putamen, thalamus, pallidum, amygdala and hippocampus. Significant, replicable negative associations between subcortical volume and alcohol use were found in the hippocampus in all youth, and the caudate and thalamus in female but not male youth, with significant interactions present in the caudate, thalamus and putamen. Findings suggest a structural vulnerability to alcohol use, or a predisposition to drink alcohol based on brain structure, with female youth potentially showing heightened risk, compared to male youth.

Impact of e-cigarette vaping aerosol exposure in pregnancy on mTOR signaling in rat fetal hippocampus

Electronic cigarette (e-cig) use during pregnancy has become a major health concern in recent years and many view them as less harmful and may help quit or reduce combustible cigarettes. Implementing a state-of-the-art engineered vaping system, comprising an atomizer similar to those sold in vape shops, we aimed to utilize a translational e-cig inhalation delivery method to provide crucial information on the impact of prenatal e-cig aerosols on the developing brain hippocampal mTOR system in a rat model system. Gestational e-cig vaping significantly increased P-mTOR levels (p < 0.05) in the rat fetal hippocampi in the nicotine group (comprising of VG/PG + nicotine) compared to the control and the juice (comprising of VG/PG) groups. Total mTOR expression was not different among groups. Immunofluorescence imaging demonstrated P-mTOR was detected exclusively in the granule cells of the dentate gyrus of the fetal hippocampus. E-cig did not alter DEPTOR, but RAPTOR and RICTOR were higher (p < 0.05) in the Nicotine group. Gestational e-cig vaping with nicotine increased (p < 0.05) the activity and expression of 4EBP1, p70S6K, but decreased (p < 0.05) P-PKCα in the fetal hippocampi. In summary, dysregulation of mTORC1 and the related mTORC2, their activity, and downstream proteins together may play a critical role in e-cig-vaping-induced neurobiological phenotypes during development.

Variation in maternal sensitivity and the development of memory biases in preschoolers

Introduction

Links between maternal sensitivity, hippocampal development, and memory abilities suggests early life insensitive care may shape structures and schemas influencing future decisions and stress management, biasing children to negative information. While it is possible that this pattern of neurodevelopment may have adaptive consequences, for example, preventing children from encountering untoward experience with future adversity, it may also leave some children at risk for the development of internalizing problems.

Methods

Here, in a Two Wave Study, we examine whether insensitive care predicts sub sequentially assessed memory biases for threatening (but not happy) stimuli in preschoolers (n = 49), and if such relations cut across different forms of relational memory, i.e., memory for relations between two "items," between an "item" and its spatial location, and an "item" and its temporal sequence. In a subset (n = 18) we also examine links between caregiving, memory, and hippocampal subregion volume.

Results

Results indicate no main or interactive influence of gender on relational memory. However, insensitive caregiving predicted the difference between Angry and Happy memory during the Item-Space condition (B = 2.451, se = 0.969, p = 0.014, 95% CI (0.572, 4.340)], as well as memory for Angry (but not Happy) items [B = -2.203, se = 0.551, p < 0.001, 95% CI (-3.264,-1.094)]. Memory for the difference between Angry and Happy stimuli in the Space condition associated with larger right hippocampal body volumes (Rho = 0.639, p = 0.004). No relations were observed with internalizing problems.

Discussion

Results are discussed with reference to developmental stage and in consideration of whether negative biases may serve as an intermediate factor linking early life insensitive care and later socioemotional problems including an increased incidence of internalizing disorders.

Genetic Specificity of Hippocampal Subfield Volumes, Relative to Hippocampal Formation, Identified in 2148 Young Adult Twins and Siblings

The hippocampus is a complex brain structure with key roles in cognitive and emotional processing and with subregion abnormalities associated with a range of disorders and psychopathologies. Here we combine data from two large independent young adult twin/sibling cohorts to obtain the most accurate estimates to date of genetic covariation between hippocampal subfield volumes and the hippocampus as a single volume. The combined sample included 2148 individuals, comprising 1073 individuals from 627 families (mean age = 22.3 years) from the Queensland Twin IMaging (QTIM) Study, and 1075 individuals from 454 families (mean age = 28.8 years) from the Human Connectome Project (HCP). Hippocampal subfields were segmented using FreeSurfer version 6.0 (CA4 and dentate gyrus were phenotypically and genetically indistinguishable and were summed to a single volume). Multivariate twin modeling was conducted in OpenMx to decompose variance into genetic and environmental sources. Bivariate analyses of hippocampal formation and each subfield volume showed that 10%-72% of subfield genetic variance was independent of the hippocampal formation, with greatest specificity found for the smaller volumes; for example, CA2/3 with 42% of genetic variance being independent of the hippocampus; fissure (63%); fimbria (72%); hippocampus-amygdala transition area (41%); parasubiculum (62%). In terms of genetic influence, whole hippocampal volume is a good proxy for the largest hippocampal subfields, but a poor substitute for the smaller subfields. Additive genetic sources accounted for 49%-77% of total variance for each of the subfields in the combined sample multivariate analysis. In addition, the multivariate analyses were sufficiently powered to identify common environmental influences (replicated in QTIM and HCP for the molecular layer and CA4/dentate gyrus, and accounting for 7%-16% of total variance for 8 of 10 subfields in the combined sample). This provides the clearest indication yet from a twin study that factors such as home environment may influence hippocampal volumes (albeit, with caveats).