Hippocampal Subregion Volumes Research Articles

Hippocampal Glutamate Levels and Their Correlation With Subregion Volume in School-Aged Children With MRI-Negative Epilepsy: A Preliminary Study.

Abnormal levels of glutamate constitute a key pathophysiologic mechanism in epilepsy. The use of glutamate chemical exchange saturation transfer (GluCEST) imaging to measure glutamate levels in pediatric epilepsy is rarely reported in research. To investigate hippocampal glutamate level variations in pediatric epilepsy and the correlation between glutamate and hippocampal subregional volumes. Cross-sectional, prospective. A total of 38 school-aged pediatric epilepsy patients with structurally normal MRI as determined by at least two independent radiologists (60% males; 8.7 ± 2.5 years; including 20 cases of focal pediatric epilepsy [FE] and 18 cases of generalized pediatric epilepsy [GE]) and 17 healthy controls (HC) (41% males; 9.0 ± 2.5 years). 3.0 T; 3D magnetization prepared rapid gradient echo (MPRAGE) and 2D turbo spin echo GluCEST sequences. The relative concentration of glutamate was calculated through pixel-wise magnetization transfer ratio asymmetry (MTRasym) analysis of the GluCEST data. Hippocampal subfield volumes were computed from MPRAGE data using FreeSurfer. This study used t tests, one-way analysis of variance, Kruskal-Wallis tests, and Pearson correlation analysis. P < 0.05 was considered statistically significant. The MTRasym values of both the left and right hippocampi were significantly elevated in GE (left: 2.51 ± 0.23 [GE] vs. 2.31 ± 0.12 [HCs], right: 2.50 ± 0.22 [GE] vs. 2.27 ± 0.22 [HCs]). The MTRasym values of the ipsilateral hippocampus were significantly elevated in FE (2.49 ± 0.28 [ipsilateral] vs. 2.29 ± 0.16 [HCs]). The MTRasym values of the ipsilateral hippocampus were significantly increased compared to the contralateral hippocampus in FE (2.49 ± 0.28 [ipsilateral] vs. 2.35 ± 0.34 [contralateral]). No significant differences in hippocampal volume were found between different groups (left hippocampus, P = 0.87; right hippocampus, P = 0.87). GluCEST imaging have potential for the noninvasive measurement of glutamate levels in the brains of children with epilepsy. 2 TECHNICAL EFFICACY: Stage 1.

Differential Vulnerability of Hippocampal Subfields to Amyloid and Tau Deposition in the Lewy Body Diseases.

Alzheimer disease (AD) copathologies of β-amyloid and tau are common in the Lewy body diseases (LBD), dementia with Lewy bodies (DLB) and Parkinson disease (PD), and target distinct hippocampal subfields compared with Lewy pathology, including subiculum and CA1. We investigated the hypothesis that AD copathologies impact the pattern of hippocampal subregion volume loss and cognitive function in LBD. This was a cross-sectional and longitudinal, single-center, observational cohort study. Participants underwent neuropsychological testing and 3T-MRI with hippocampal segmentation using FreeSurferV7. PiB-PET and flortaucipir-PET imaging of comorbid β-amyloid (A) and tau (T) were acquired. The association of functional cognition, β-amyloid, and tau loads with hippocampal subregion volume was assessed. The contribution of subregion volumes to the relationship of AD-related deposits on functional cognition was examined with mediation analysis. The effects of AD-related deposits on the rate of subregion atrophy were evaluated with mixed-effects models. Of 103 participants (mean age: 70.3 years; 37.3% female), 52 had LBD with impaired cognition (LBD-I), 26 had normal cognition (LBD-N), and 25 were A- healthy controls (HCs). Volumes of hippocampal subregions prone to AD copathologies, including subiculum (F = 6.9, p = 0.002), presubiculum (F = 7.3, p = 0.001), and parasubiculum (F = 5.9, p = 0.004), were reduced in LBD-I compared with LBD-N and HC. Volume was preserved in CA2/3, Lewy pathology susceptible subregions. In LBD-I, reduced CA1, subiculum, and presubiculum volumes were associated with greater functional cognitive impairment (all p < 0.05). Compared with HC, subiculum volume was reduced in A+T+ but not A-T- participants (F = 2.62, p = 0.043). Reduced subiculum volume mediated the effect of amyloid on functional cognition (0.12, 95% CI: 0.005 to 0.26, p = 0.040). In 26 longitudinally-evaluated participants, baseline tau deposition was associated with faster CA1 (p = 0.021) and subiculum (p = 0.002) atrophy. In LBD, volume loss in hippocampal output subregions-particularly the subiculum-is associated with functional cognition and AD-related deposits. Tau deposition appears to accelerate subiculum and CA1 atrophy, whereas Aβ does not. Subiculum volume may have value as a biomarker of AD copathology-mediated neurodegeneration and disease progression.

Atrophy patterns in hippocampal subregions and their relationship with cognitive function in fibromyalgia patients with mild cognitive impairment

ObjectivesFibromyalgia (FM) has been associated with decreased hippocampal volume; however, the atrophy patterns of hippocampal subregions have not yet been identified. We therefore aimed to evaluate the volumes of hippocampal subregions in FM patients with mild cognitive impairment (MCI), and to explore the relationship between different subregional alterations and cognitive function.MethodsThe study included 35 FM patients (21 with MCI and 14 without MCI) and 35 healthy subjects. All subjects performed the Montreal Cognitive Assessment (MoCA) to assess cognitive function. FreeSurfer V.7.3.2 was used to calculate hippocampal subregion volumes. We then compared hippocampal subregion volumes between the groups, and analyzed the relationship between hippocampal subregion volume and cognitive function using a partial correlation analysis method.ResultsCompared with the healthy subjects, FM patients with MCI had smaller hippocampal volumes in the left and right CA1 head, Molecular layer head, GC-DG head, and CA4 head, and in the left Presubiculum head. Poorer executive function, naming ability, and attention were associated with left CA1 head and left Molecular layer head atrophy. By contrast, hippocampal subregion volumes in the FM patients without MCI were slightly larger than or similar to those in the healthy subjects, and were not significantly correlated with cognitive function.ConclusionSmaller volumes of left CA1 head and left Molecular layer head were associated with poorer executive function, naming ability, and attention in FM patients with MCI. However, these results were not observed in the FM patients without MCI. These findings suggest that the hippocampal subregions of FM patients might present compensatory mechanisms before cognitive decline occurs.

Hippocampal subfields in remitted schizophrenia.

Current evidence of volume changes in hippocampal subdivisions in schizophrenia remains inconsistent, and few studies have investigated the relationship between regional hippocampal volumes and symptom remission. In this cross-sectional study, we recruited 31 patients with schizophrenia and 31 healthy controls (HCs). Symptomatic remission in schizophrenia was determined according to Remission in Schizophrenia Working Group criteria. The volumes of hippocampal longitudinal subregions and transverse subfields were measured using manual and automatic techniques, respectively. Between-group regional hippocampal volume differences were analyzed using multivariate analysis of covariance followed by univariate analysis of covariance. Compared with the HCs, the patients with schizophrenia had smaller bilateral heads and tails along the longitudinal axis; they also had reduced volumes of the bilateral CA1, CA3, CA4, GC-ML-DG, molecular layer, tail, left subiculum, left HATA, and right parasubiculum along the transverse axis in the hippocampus (all corrected p < 0.05). Furthermore, compared with the HCs and patients with remitted schizophrenia, the patients with nonremitted schizophrenia had smaller bilateral hippocampal tail subfields (corrected p < 0.05). Our results indicated that the pathophysiology and symptomatic remission of schizophrenia are related to changes in the volumes of hippocampal subdivisions. These volume changes might be clinically relevant as biomarkers for schizophrenia identification and treatment.

Selective vulnerability of hippocampal sub-regions in patients with subcortical vascular mild cognitive impairment.

Early diagnosis of subcortical vascular mild cognitive impairment (svMCI) is clinically essential because it is the most reversible subtype of all cognitive impairments. Since structural alterations of hippocampal sub-regions have been well studied in neurodegenerative diseases with pathophysiological cognitive impairments, we were eager to determine whether there is a selective vulnerability of hippocampal sub-fields in patients with svMCI. Our study included 34 svMCI patients and 34 normal controls (NCs), with analysis of T1 images and Montreal Cognitive Assessment (MoCA) scores. Gray matter volume (GMV) of hippocampal sub-regions was quantified and compared between the groups, adjusting for age, sex, and education. Additionally, we explored correlations between altered GMV in hippocampal sub-fields and MoCA scores in svMCI patients. Patients with svMCI exhibited selectively reduced GMV in several left hippocampal sub-regions, such as the hippocampal tail, hippocampal fissure, CA1 head, ML-HP head, CA4 head, and CA3 head, as well as decreased GMV in the right hippocampal tail. Specifically, GMV in the left CA3 head was inversely correlated with MoCA scores in svMCI patients. Our findings indicate that the atrophy pattern of patients with svMCI was predominantly located in the left hippocampal sub-regions. The left CA3 might be a crucial area underlying the distinct pathophysiological mechanisms of cognitive impairments with subcortical vascular origins.

Cannabis Dependence is Associated with Reduced Hippocampal Subregion Volumes Independently of Sex: Findings from an ENIGMA Addiction Working Group Multi-Country Study.

Background: Males and females who consume cannabis can experience different mental health and cognitive problems. Neuroscientific theories of addiction postulate that dependence is underscored by neuroadaptations, but do not account for the contribution of distinct sexes. Further, there is little evidence for sex differences in the neurobiology of cannabis dependence as most neuroimaging studies have been conducted in largely male samples in which cannabis dependence, as opposed to use, is often not ascertained. Methods: We examined subregional hippocampus and amygdala volumetry in a sample of 206 people recruited from the ENIGMA Addiction Working Group. They included 59 people with cannabis dependence (17 females), 49 cannabis users without cannabis dependence (20 females), and 98 controls (33 females). Results: We found no group-by-sex effect on subregional volumetry. The left hippocampal cornu ammonis subfield 1 (CA1) volumes were lower in dependent cannabis users compared with non-dependent cannabis users (p<0.001, d=0.32) and with controls (p=0.022, d=0.18). Further, the left cornu ammonis subfield 3 (CA3) and left dentate gyrus volumes were lower in dependent versus non-dependent cannabis users but not versus controls (p=0.002, d=0.37, and p=0.002, d=0.31, respectively). All models controlled for age, intelligence quotient (IQ), alcohol and tobacco use, and intracranial volume. Amygdala volumetry was not affected by group or group-by-sex, but was smaller in females than males. Conclusions: Our findings suggest that the relationship between cannabis dependence and subregional volumetry was not moderated by sex. Specifically, dependent (rather than non-dependent) cannabis use may be associated with alterations in selected hippocampus subfields high in cannabinoid type 1 (CB1) receptors and implicated in addictive behavior. As these data are cross-sectional, it is plausible that differences predate cannabis dependence onset and contribute to the initiation of cannabis dependence. Longitudinal neuroimaging work is required to examine the time-course of the onset of subregional hippocampal alterations in cannabis dependence, and their progression as cannabis dependence exacerbates or recovers over time.

Volumetric analysis of hippocampal subregions and subfields in left and right semantic dementia.

Two variants of semantic dementia are recognized based on the laterality of temporal lobe involvement: a left-predominant variant associated with verbal knowledge impairment and a right-predominant variant associated with behavioural changes and non-verbal knowledge loss. This cross-sectional clinicoradiologic study aimed to assess whole hippocampal, subregion, and/or subfield volume loss in semantic dementia versus controls and across its variants. Thirty-five semantic dementia participants and 15 controls from the Neurodegenerative Research Group at Mayo Clinic who had completed 3.0-T volumetric magnetic resonance imaging and 18F-fluorodeoxyglucose-positron emission tomography were included. Classification as left-predominant (n = 25) or right-predominant (n = 10) variant was based on temporal lobe hypometabolism. Volumes of hippocampal subregions (head, body, and tail) and subfields (parasubiculum, presubiculum, subiculum, cornu ammonis 1, cornu ammonis 3, cornu ammonis 4, dentate gyrus, molecular layer, hippocampal-amygdaloid transition area, and fimbria) were obtained using FreeSurfer 7. Subfield volumes were measured separately from head and body subregions. We fit linear mixed-effects models using log-transformed whole hippocampal/subregion/subfield volumes as dependent variables; age, sex, total intracranial volume, hemisphere and a group-by-hemisphere interaction as fixed effects; and subregion/subfield nested within hemisphere as a random effect. Significant results (P < 0.05) are hereby reported. At the whole hippocampal level, the dominant (predominantly involved) hemisphere of both variants showed 23-27% smaller volumes than controls. The non-dominant (less involved) hemisphere of the right-predominant variant also showed volume loss versus controls and the left-predominant variant. At the subregional level, both variants showed 17-28% smaller dominant hemisphere head, body, and tail than controls, with the right-predominant variant also showing 8-12% smaller non-dominant hemisphere head than controls and left-predominant variant. At the subfield level, the left-predominant variant showed 12-36% smaller volumes across all dominant hemisphere subfields and 14-15% smaller non-dominant hemisphere parasubiculum, presubiculum (head and body), subiculum (head) and hippocampal-amygdaloid transition area than controls. The right-predominant variant showed 16-49% smaller volumes across all dominant hemisphere subfields and 14-22% smaller parasubiculum, presubiculum, subiculum, cornu ammonis 3, hippocampal-amygdaloid transition area (all from the head) and fimbria of non-dominant hemisphere versus controls. Comparison of dominant hemispheres showed 16-29% smaller volumes of the parasubiculum, presubiculum (head) and fimbria in the right-predominant than left-predominant variant; comparison of non-dominant hemispheres showed 12-15% smaller cornu ammonis 3, cornu ammonis 4, dentate gyrus, hippocampal-amygdaloid transition area (all from the head) and cornu ammonis 1, cornu ammonis 3 and cornu ammonis 4 (all from the body) in the right-predominant variant. All hippocampal subregion/subfield volumes are affected in semantic dementia, although some are more affected in both dominant and non-dominant hemispheres of the right-predominant than the left-predominant variant by the time of presentation. Involvement of hippocampal structures is apparently more subregion dependent than subfield dependent, indicating possible superiority of subregion volumes as disease biomarkers.

Atrophy of hippocampal subfields and amygdala nuclei in subjects with mild cognitive impairment progressing to Alzheimer's disease

The hippocampus and amygdala are the first brain regions to show early signs of Alzheimer's Disease (AD) pathology. AD is preceded by a prodromal stage known as Mild Cognitive Impairment (MCI), a crucial crossroad in the clinical progression of the disease. The topographical development of AD has been the subject of extended investigation. However, it is still largely unknown how the transition from MCI to AD affects specific hippocampal and amygdala subregions. The present study is set to answer that question. We analyzed data from 223 subjects: 75 healthy controls, 52 individuals with MCI, and 96 AD patients obtained from the ADNI. The MCI group was further divided into two subgroups depending on whether individuals in the 48 months following the diagnosis either remained stable (N = 21) or progressed to AD (N = 31). A MANCOVA test evaluated group differences in the volume of distinct amygdala and hippocampal subregions obtained from magnetic resonance images. Subsequently, a stepwise linear discriminant analysis (LDA) determined which combination of magnetic resonance imaging parameters was most effective in predicting the conversion from MCI to AD. The predictive performance was assessed through a Receiver Operating Characteristic analysis. AD patients displayed widespread subregional atrophy. MCI individuals who progressed to AD showed selective atrophy of the hippocampal subiculum and tail compared to stable MCI individuals, who were undistinguishable from healthy controls. Converter MCI showed atrophy of the amygdala's accessory basal, central, and cortical nuclei. The LDA identified the hippocampal subiculum and the amygdala's lateral and accessory basal nuclei as significant predictors of MCI conversion to AD. The analysis returned a sensitivity value of 0.78 and a specificity value of 0.62. These findings highlight the importance of targeted assessments of distinct amygdala and hippocampus subregions to help dissect the clinical and pathophysiological development of the MCI to AD transition.

Hippocampal Subregions Volume and Texture for the Diagnosis of Mild Cognitive Impairment

ABSTRACT The aim was to examine the diagnostic efficacy of hippocampal subregions volume and texture in differentiating amnestic mild cognitive impairment (MCI) from normal aging changes. Ninety MCI subjects and eighty-eight well-matched healthy controls (HCs) were selected. Twelve hippocampal subregions volume and texture features were extracted using Freesurfer and MaZda based on T1 weighted MRI. Then, two-sample t-test and Least Absolute Shrinkage and Selection Operator (LASSO) regression were developed to select a subset of the original features. Support vector machine (SVM) was used to perform the classification task and the area under the curve (AUC), sensitivity, specificity and accuracy were calculated to evaluate the diagnostic efficacy of the model. The volume features with high discriminative power were mainly located in the bilateral CA1 and CA4, while texture feature were gray-level non-uniformity, run length non-uniformity and fraction. Our model based on hippocampal subregions volume and texture features achieved better classification performance with an AUC of 0.90. The volume and texture of hippocampal subregions can be utilized for the diagnosis of MCI. Moreover, we found that the features that contributed most to the model were mainly textural features, followed by volume. These results may guide future studies using structural scans to classify patients with MCI.

Atrophy patterns in hippocampus and amygdala subregions of depressed patients with Parkinson's disease

We aimed to explore the subregional atrophy patterns of the amygdala and hippocampus in Parkinson's disease (PD) with depression and their correlation with the severity of the depressive symptom. MRI scans were obtained for 34 depressed PD patients (DPD), 22 nondepressed PD patients (NDPD), and 28 healthy controls (HC). Amygdala and hippocampal subregions were automatically segmented, and the intergroup volume difference was compared. The relationships between the volumes of the subregions and depression severity were investigated. Logistic analysis and Receiver operator characteristic curve were used to find independent predictors of DPD. Compared with the HC group, atrophy of the bilateral lateral nucleus, left accessory basal nucleus, right cortical nucleus, right central nucleus, and right medial nucleus subregions of the amygdala were visible in the DPD group, while the right lateral nucleus subregion of the amygdala was smaller in the DPD group than in the NDPD group. The DPD group showed significant atrophy in the left molecular layer, left GC-DG, left CA3, and left CA4 subregions compared with the HC group for hippocampal subregion volumes. Also, the right lateral nuclei volume and disease duration were independent predictors of DPD. To sum up, DPD patients showed atrophy in multiple amygdala subregions and left asymmetric hippocampal subregions. The decreased amygdala and hippocampal subregion volumes were correlated with the severity of depressive symptoms. The volume of right lateral nuclei and disease duration could be used as a biomarker to detect DPD.

Depression and Hippocampal Subfield Volume in Older Adults

AbstractBackgroundMajor Depressive Disorder (MDD) is associated with higher risk for developing Alzheimer’s Disease (AD), (Bennett &amp; Thomas, 2014). Both conditions are associated with smaller hippocampal subfield volumes, and both preferentially affect females (Shi et al., 2021). We examined the relationship between depression diagnosis and hippocampal subfield volume, by carrier status for AD genetic risk variant APOE4 and sex. We hypothesized that the association between depression and subfield volume would be stronger in females due to the higher rate of depression.MethodWe examined 1726 cognitively intact older adults from the Health and Aging Brain Study ‐ Health Disparities (HABS‐HD) cohort (Table1) who had available hippocampal high resolution MRI scans (Siemens Skyra or Vida‐3T). Scans were segmented into CA1, CA23DG, and subiculum using Automatic Segmentation of Hippocampal Subfields (ASHS) software and subfield volume was averaged bilaterally. We used separate multiple linear regressions to assess the association between depression and each hippocampal subfield volume, covarying for age, sex, years of education, number of MRI slices segmented, intracranial volume, and scanner. We corrected for multiple comparisons across regions using FDR correction. We also evaluated CA1 and CA23DG volume to depression diagnosis, stratifying by APOE4 positivity and sex and testing for formal interactions.ResultSee Table 2 for results. Depression was associated with smaller CA1 and CA23DG volume across all participants. Depression was associated with smaller CA1 and CA23DG in the APOE4 negative group, but not the APOE4 positive group. The depression by APOE4 interaction was significant for CA23DG volume (𝛽 = 0.25, p = 0.049). Depression was associated with smaller CA1 and CA23DG volumes in males, but not in females, with trend level interaction effects in the CA1 (𝛽 = 0.13, p = 0.095) and CA23DG (𝛽 = 0.17, p = 0.067).ConclusionDepression was associated with smaller CA1 and CA23DG volumes in older adults consistent with past literature. In contrast to our hypotheses, depression was associated with lower hippocampal subregional volumes more in those with lower risk for Alzheimer’s disease (male and APOE4‐ adults).Variability induced by other AD risk factors may mask the relationship between depression and hippocampal subregion volume when AD risk is higher.

Shared and unique heritability of hippocampal subregion volumes in children and adults

Behavioral genetic analyses have not demonstrated robust, unique, genetic correlates of hippocampal subregion volume. Genetic differentiation of hippocampal longitudinal axis subregion volume has not yet been investigated in population-based samples, although this has been demonstrated in rodent and post-mortem human tissue work. The following study is the first population-based investigation of genetic factors that contribute to gray matter volume along the hippocampal longitudinal axis. Twin-based biometric analyses demonstrated that longitudinal axis subregions are associated with significant, unique, genetic variance, and that longitudinal axis subregions are also associated with significant shared, hippocampus-general, genetic factors. Our study’s findings suggest that genetic differences in hippocampal longitudinal axis structure can be detected in individual differences in gray matter volume in population-level research designs.

58 Hippocampal Subregions Predict Executive Function Across the Adult Lifespan

Objective:Executive function is known to decline in later life, largely attributed to structural and functional changes in the prefrontal cortex. However, other regions of the brain are integral to executive functioning, including the hippocampus. The hippocampus plays a large role in memory but its intricate connections to limbic regions including the prefrontal cortex likely underlies associations between the hippocampus and executive functions. Due to the hippocampus’ complex structure, hippocampal subregions may be differentially associated with executive function, but this possibility remains largely unexplored. Therefore, we examined the association between volume of the hippocampus and its subregions with executive function to understand these relationships across the adult lifespan.Participants and Methods:The study included 32 healthy, community-dwelling participants (age range = 18-81, mean age = 51.06 ± 20.98, 91% white, 72% female) who received a 3-Tesla magnetic resonance imaging (MRI) scan and completed a cognitive battery. We calculated an executive composite based on Trail Making Test Part B and the interference score from the Stroop Color and Word Test. Freesurfer (version 5.3) as used to quantify total hippocampal volume and subfield volumes for CA1, CA2-3, CA4-dentate gyrus, subiculum, and presubiculum. We conducted mixed-effects regression analyses with total hippocampal and subfield volume, age group (young, middle-aged, and older), and their interaction predicting the executive function composite, controlling for total intracranial volume.Results:Larger hippocampal subregion volumes in CA1 (p = 0.03), the subiculum (p = 0.01), and the CA4-dentate gyrus (p = 0.04) predicted better executive function. Total hippocampal volume and the presubiculum were not significantly associated with the executive function composite. The age group interaction was not significant for any of the models. Follow-up analyses by hemisphere showed that the effects were right lateralized in CA1and CA4-dentate gyrus, and bilateral in the subiculum.Conclusions:These data support the literature demonstrating the involvement of the hippocampus in executive function and demonstrates variation across hippocampal subfields. The lack of significant age interactions suggests these relationships may not differ across the lifespan, although this finding would need to be replicated in larger samples. These findings support previous literature showing CA4-dentate gyrus’ association with neurogenesis may facilitate better executive function by increasing connection strength among CA1, CA2-3, and the frontal cortex. This study contributes to our understanding of how specific hippocampal subregions relate to executive function, which has both clinical and research implications.

Contributions of hippocampal subfields and subregions to episodic memory performance in healthy cognitive aging

In the present study we investigated whether hippocampal subfield (cornu ammonis 1–3, dentate gyrus, and subiculum) and anteroposterior hippocampal subregion (head,body, and tail) volumes can predict episodic memory function using high-field high resolution structural magnetic resonance imaging (MRI). We recruited 126 healthy participants (18–85 years). MRI datasets were collected on a 4.7 T system. Participants were administered the Wechsler Memory Scale (WMS–IV) to evaluate episodic memory function. Structural equation modeling was used to test the relationship between studied variables. We found that the volume of the dentate gyrus subfield and posterior hippocampus (body) showed a significant direct effect on visuospatial memory performance; additionally, an indirect effect of age on visuospatial memory mediated through these hippocampal subfield/subregion was significant. Logical and verbal memory were not significantly associated with hippocampal subfield or subregion volumes.

Altered hippocampal subfield volumes in major depressive disorder with and without anhedonia

BackgroundPrevious neuroimaging findings have demonstrated the association between anhedonia and the hippocampus. However, few studies have focused on the structural changes in the hippocampus in major depressive disorder (MDD) patients with anhedonia. Meanwhile, considering that multiple and functionally specialized subfields of the hippocampus have their own signatures, the present study aimed to investigate the volumetric alterations of the hippocampus as well as its subfields in MDD patients with and without anhedonia.MethodsA total of 113 subjects, including 30 MDD patients with anhedonia, 40 MDD patients without anhedonia, and 43 healthy controls (HCs), were recruited in the study. All participants underwent high-resolution brain magnetic resonance imaging (MRI) scans, and the automated hippocampal substructure module in FreeSurfer 6.0 was used to evaluate the volumes of hippocampal subfields. We compared the volumetric differences in hippocampal subfields among the three groups by analysis of variance (ANOVA, post hoc Bonferroni), and partial correlation was used to explore the association between hippocampal subregion volumes and clinical characteristics.ResultsANOVA showed significant volumetric differences in the hippocampal subfields among the three groups in the left hippocampus head, mainly in the cornu ammonis (CA) 1, granule cell layer of the dentate gyrus (GC-ML-DG), and molecular layer (ML). Compared with HCs, both groups of MDD patients showed significantly smaller volumes in the whole left hippocampus head. Interestingly, further exploration revealed that only MDD patients with anhedonia had significantly reduced volumes in the left CA1, GC-ML-DG and ML when compared with HCs. No significant difference was found in the volumes of the hippocampal subfields between MDD patients without anhedonia and HCs, either the two groups of MDD patients. However, no association between hippocampal subfield volumes and clinical characteristics was found in either the subset of patients with anhedonia or in the patient group as a whole.ConclusionsThese preliminary findings suggest that MDD patients with anhedonia exhibit unique atrophy of the hippocampus and that subfield abnormalities in the left CA1 and DG might be associated with anhedonia in MDD.

GluCEST Imaging and Structural Alterations of the Bilateral Hippocampus in First-Episode and Early-Onset Major Depression Disorder.

Glutamate dysregulation is one of the key pathogenic mechanisms of major depressive disorder (MDD), and glutamate chemical exchange saturation transfer (GluCEST) has been used for glutamate measurement in some brain diseases but rarely in depression. To investigate the GluCEST changes in hippocampus in MDD and the relationship between glutamate and hippocampal subregional volumes. Cross-sectional. Thirty-two MDD patients (34% males; 22.03 ± 7.21 years) and 47 healthy controls (HCs) (43% males; 22.00 ± 3.28 years). 3.0 T; magnetization prepared rapid gradient echo (MPRAGE) for three-dimensional T1-weighted images, two-dimensional turbo spin echo GluCEST, and multivoxel chemical shift imaging (CSI) for proton magnetic resonance spectroscopy (1 H MRS). GluCEST data were quantified by magnetization transfer ratio asymmetry (MTRasym ) analysis and assessed by the relative concentration of 1 H MRS-measured glutamate. FreeSurfer was used for hippocampus segmentation. The independent sample t test, Mann-Whitney U test, Spearman's correlation, and partial correlation analysis were used. P < 0.05 was considered statistically significant. In the left hippocampus, GluCEST values were significantly decreased in MDD (2.00 ± 1.08 [MDD] vs. 2.62 ± 1.41 [HCs]) and showed a significantly positive correlation with Glx/Cr (r = 0.37). GluCEST values were significantly positively correlated with the volumes of CA1 (r = 0.40), subiculum (r = 0.40) in the left hippocampus and CA1 (r = 0.51), molecular_layer_HP (r = 0.50), GC-ML-DG (r = 0.42), CA3 (r = 0.44), CA4 (r = 0.44), hippocampus-amygdala-transition-area (r = 0.46), and the whole hippocampus (r = 0.47) in the right hippocampus. Hamilton Depression Rating Scale scores showed significantly negative correlations with the volumes of the left presubiculum (r = -0.40), left parasubiculum (r = -0.47), and right presubiculum (r = -0.41). GluCEST can be used to measure glutamate changes and help to understand the mechanism of hippocampal volume loss in MDD. Hippocampal volume changes are associated with disease severity. 2 TECHNICAL EFFICACY: Stage 1.

Polygenic Risk for Schizophrenia, Major Depression, and Post-traumatic Stress Disorder and Hippocampal Subregion Volumes in Middle Childhood.

Studies demonstrate that individuals with diagnoses for Major Depressive Disorder (MDD), Post-traumatic Stress Disorder (PTSD), and Schizophrenia (SCZ) may exhibit smaller hippocampal gray matter relative to otherwise healthy controls, although the effect sizes vary in each disorder. Existing work suggests that hippocampal abnormalities in each disorder may be attributable to genetic liability and/or environmental variables. The following study uses baseline data from the Adolescent Brain and Cognitive Development[Formula: see text] Study (ABCD Study[Formula: see text]) to address three open questions regarding the relationship between genetic risk for each disorder and hippocampal volume reductions: (a) whether polygenic risk scores (PGRS) for MDD, PTSD, and SCZ are related to hippocampal volume; (b) whether PGRS for MDD, PTSD, and SCZ are differentially related to specific hippocampal subregions along the longitudinal axis; and (c) whether the association between PGRS for MDD, PTSD, and SCZ and hippocampal volume is moderated by sex and/or environmental adversity. In short, we did not find associations between PGRS for MDD, PTSD, and SCZ to be significantly related to any hippocampal subregion volumes. Furthermore, neither sex nor enviornmental adversity significantly moderated these associations. Our study provides an important null finding on the relationship genetic risk for MDD, PTSD, and SCZ to measures of hippocampal volume.

Insulin and hippocampal subregion volume in older adults

AbstractBackgroundType 2 diabetes (DM) is a risk factor for Alzheimer's disease (AD) and other dementias. DM, which is more common in Mexican Americans (MA) than non‐Hispanic Whites (NHW), is associated with high blood glucose levels and often with hyperinsulinemia. Hippocampal volume is an early neuroimaging marker of AD. We examined the relationship of blood insulin with hippocampal subregion volumes in MA and NHW.MethodIn a sample of 1588 older adults without dementia (age: 50‐92 years; 826 MA, 762 NHW; 387 DM, 1201 non‐DM; 1344 cognitively normal, 244 mild cognitive impairment; 613M/975F) from the Health and Aging Brain Study ‐ Health Disparities (HABS‐HD) cohort, we assessed whether fasting plasma insulin and glucose levels were associated with the volume of left and right hippocampal body subregions (CA1, CA23DG, subiculum) using hippocampal high resolution 3T MRI scans (Siemens 3T). We further examined the significant insulin relationship with CA23DG volume by ethnicity and diabetes diagnostic group. We used a multiple linear regression model, covarying for age, sex, cognitive diagnosis, diabetic status, years of education, number of MRI slices segmented, and intracranial volume. All p values were FDR corrected for multiple comparisons across regions.ResultHigher insulin levels were associated with a smaller volume in right and left CA23DG (right: FDR p=0.015, left: FDR p=0.015) across all participants. Glucose levels were not significantly associated with hippocampal subregion volume (Table 1). When we further investigated the significant relationship between insulin and CA23DG volume by ethnic group and diabetic status, we found that higher insulin was associated with lower CA23DG volume in NHW (right: p=0.014, left: p=0.013), MA (right only: p=0.034, left: p=0.115), and in non‐diabetics (right: p=0.027, left trend: p=0.056) (Figure 1).ConclusionHigher insulin levels were associated with lower CA23DG volume in older adults without dementia, with the strength of the negative association between blood insulin levels and hippocampal subfield volume varying by diabetic status.

Correlations between Hippocampus and Cognitive Score in Patients with Carotid Artery Stenosis Based on Resting State Functional Magnetic Resonance Imaging

Objective To investigate the correlations among brain functional connectivity,hippocampal subregion volume and cognitive score in the patients with carotid artery stenosis(CAS)based on resting state functional magnetic resonance imaging.Methods Forty CAS patients treated in the Nanjing Drum Tower Hospital Affiliated to Medical School of Nanjing University from January to December in 2019 and 31 healthy volunteers were enrolled in this study.All the participants underwent cognitive assessment,structural MRI for the measurement of hippocampal volume,and resting state functional magnetic resonance imaging for the examination of brain functional connectivity(FC).We compared the cognitive function,hippocampal subregion volumes,and brain functional connectivity between the two groups and investigated the correlations between the three indicators.Results The CAS patients had lower mini-mental state examination(MMSE)(F=13.346,P=0.001)and Montreal cognitive assessment(MoCA)(F=52.005,P<0.001)scores than the healthy volunteers.Compared with healthy volunteers,CAS patients showed small whole hippocampus(right side:t=2.176,P=0.033;left side:t=2.881,P=0.005;especially on the left side),small hippocampal tail(right side:t=2.394,P=0.019;left side:t=3.158,P=0.002),small hippocampal body(right side:t=2.336,P=0.022;left side:t=3.165,P=0.002),small subiculum(right side:t=2.211,P=0.030;left side:t=2.430;P=0.018),and small molecular layer(right side:t=2.103,P=0.039;left side:t=2.702,P=0.009).The whole hippocampal volume was positively correlated with MoCA and MMSE scores(left MoCA:r=0.289,P=0.015;right MMSE:r=0.249,P=0.038;left MMSE:r=0.316,P=0.008).The volume changes in the subiculum,presubiculum,and left molecular layer were positively correlated with MoCA(right subiculum:r=0.290,P=0.015;left subiculum:r=0.382,P=0.001;right presubiculum:r=0.293,P=0.014;left presubiculum:r=0.440,P<0.001;left molecular layer:r=0.259,P=0.031)and MMSE scores(right subiculum:r=0.278,P=0.020;left subiculum:r=0.419,P<0.001;right presubiculum:r=0.296,P=0.013;left presubiculum:r=0.506,P<0.001;left molecular layer:r=0.298,P=0.012),while the volume changes in the remaining hippocampal subregions were not correlated with cognitive scores(all P>0.05).Compared with healthy volunteers,the CAS patients presented low FC values of the left hippocampus to the occipital lobe and frontal lobe and of right hippocampus to the occipital lobe,temporal lobe,prefrontal lobe,and middle frontal gyrus(Gaussian random field correction,voxel P<0.01,cluster P<0.05).The volume changes of the left whole hippocampus,hippocampal head,and cornu ammonis 1(CA1)were positively correlated with the FC value of right hippocampus to the temporal lobe(left whole hippocampus:r=0.358,P=0.025;right hippocampal head:r=0.325,P=0.044;left hippocampal head:r=0.360,P=0.024;right CA1:r=0.326,P=0.043;left CA1:r=0.341,P=0.034).MoCA and MMSE scores were positively correlated with the FC value of right hippocampus to the frontal lobe(MoCA middle frontal gyrus:r=0.389,P=0.014;MoCA prefrontal lobe:r=0.363,P=0.023;MMSE prefrontal lobe:r=0.321,P=0.046).Conclusions CAS patients have different levels of cognitive impairment.Hippocampal atrophy and a decline in the FC value of hippocampus to the occipital lobe may play a role in cognitive impairment in CAS patients.This discovery lays a foundation for the future research on the mechanism of cognitive dysfunction in CAS patients.

Hippocampal subregional thinning related to tau pathology in early stages of Alzheimer’s disease

AbstractBackgroundSubregions in the medial temporal lobe (MTL) are affected early by Alzheimer’s disease (AD) pathology and subject to grey matter atrophy. Measuring the earliest AD‐related atrophy in the hippocampus is challenging as region‐of‐interest (ROI) analyses of hippocampal subregional volumes collapse across voxels within anatomical subregions. PET imaging studies, however, report accumulation of tau pathology between anatomical subregions in the earliest disease stages (Berron et al., 2021) fitting reports from the neuropathological literature (Lace et al., 2019; Ravikumar et al., 2021). Thus, sensitive in vivo methods of point‐wise structural measures are needed in order to detect the earliest hippocampal thinning in AD along the anterior‐posterior as well as the medial‐lateral hippocampal axis.MethodHere we analyzed data from 76 amyloid‐beta negative (Ab‐) cognitively normal (CN), 46 Ab+ CN individuals and 25 Ab+ patients with mild cognitive impairment (MCI) from the BioFINDER‐2 study, who underwent 7 Tesla T2‐weighted structural magnetic resonance imaging, tau positron emission tomography imaging (using 18F‐RO‐948) and cognitive assessments. First, we segmented hippocampal subfields and extrahippocampal subregions. Second, we calculated point‐wise hippocampal thickness estimates (Diers et al.) of hippocampal subfields subiculum, cornu ammonis (CA)1, CA2 and CA3 on the level of the hippocampal body. Thirdly, we extracted local tau‐PET SUVR from Area 35 (A35), entorhinal cortex and amygdala. Finally, we assessed relationships between hippocampal local thickness and tau accumulation as well as cognitive performance.ResultOur analyses revealed earliest hippocampal thinning associated with tau accumulation in an area spanning the boundary of subiculum and CA1 at the level of the anterior hippocampal body. Ab+ MCI patients showed more posterior thinning in comparison to Ab‐ CU participants. Median thickness in an ROI comprising vertices with A35 tau‐related thinning (A35‐TauThinning‐ROI) was significantly lower in MCI Ab+ and tended to be lower in CU Ab+ compared to CU Ab‐. Higher median thickness in the hippocampal A35‐TauThinning‐ROI, but not whole CA1 nor subiculum thickness, was associated with better 10‐Word‐Delayed‐Recall and higher PACC scores.ConclusionOur results suggest that tau‐related thinning of hippocampal subregions can be observed already in early disease stages. Tau‐related point‐wise thickness measures were more sensitive compared to volumetric measures of anatomical subregions.