Hippocampal volume, and the anterior-posterior sub regions relates to recall and recognition over five years: Bidirectional brain-behaviour associations

Associations Between Episodic Memory and Hippocampal Volume in Late Adulthood

Different tasks of episodic memory (EM) are only moderately correlated with each other. Furthermore, various EM tasks exhibit disproportional relationships with the hippocampus. This study examined the covariance structure of EM tasks and assessed whether this structure relates differently to hippocampal volume (HV) in a sample of 648 cognitively unimpaired older adults (mean age = 69.88). A confirmatory factor analysis (CFA) and linear regression models were used to test the associations between the observed factors of EM and HV. A model with three first-order subfactors (immediate verbal recall, delayed verbal recall, and visuospatial) derived from a second-order EM domain factor satisfied model fit (χ2 p value ≥ 0.05, CFI > 0.90, RMSEA < 0.08, SRMR < 0.08). Total, left, and right HV explained a similar amount of variance in all EM subfactors. CA1, CA3, subiculum, and entorhinal cortex volume were associated with all subfactors, while CA2 and dentate gyrus volume were not associated with EM. These results suggest that EM tasks are measuring the same construct, but different complex processes contribute to EM. Furthermore, HV accounted for a small portion of the variance in EM, suggesting that HV might not be a useful marker of EM in cognitively unimpaired older adults. Finally, this study provides evidence that various hippocampal subfield volumes may not be purely associated with any one aspect of EM processing.

Association of hippocampal atrophy with tau pathology of temporal regions in preclinical Alzheimer's disease

BackgroundHippocampal atrophy is linked to memory and cognitive deficits, preceding clinical diagnosis of mild cognitive impairment (MCI) by decades. Morphometry changes in the hippocampal formation (HF) and their relationship to tau deposition in non-demented individuals remains unclear.ObjectiveTo investigate morphometry changes in the HF and their association with tau deposition in a non-demented cohort.MethodsEighty-three subjects from the Alzheimer's Disease Neuroimaging Initiative (ADNI) underwent T1-weighted MRI and Tau-PET scans at baseline and longitudinal follow-up. Participants were divided into amyloid-negative (Aβ-) and amyloid-positive (Aβ+) groups. Hippocampal volume/thickness were measured, and associations with tau deposition in temporal regions were examined using multivariable linear regression.ResultsNo significant association was found between the hippocampal volume/thickness and tau deposition of temporal regions for the Aβ- group. For the Aβ+ group, the hippocampal thickness was significantly associated with tau deposition of entorhinal cortex (ERC) for both hemispheres, and temporal pole, inferior temporal, and middle temporal regions for right hippocampi with the longitudinal follow up scans, while no significant association with the baseline scans. It was interesting that there was strong association between the baseline tau deposition of ERC and temporal pole and the longitudinal follow up thickness of left hippocampi, while the associated regions for the right hemisphere were ERC, temporal pole, and inferior temporal regions.ConclusionsHippocampal atrophy may precede cognitive symptoms, with tau deposition in adjacent temporal regions contributing to hippocampal changes. The right HF appears more vulnerable than the left, indicating hemispheric differences in pathology.

Brain functional changes across mood states in bipolar disorder: from a large-scale network perspective

BACKGROUND

Exploring the neural basis related to different mood states is a critical issue for understanding the pathophysiology underlying mood switching in bipolar disorder (BD), but research has been scarce and inconsistent.

METHODS

Resting-state functional magnetic resonance imaging data were acquired from 162 patients with BD: 33 (hypo)manic, 64 euthymic, and 65 depressive, and 80 healthy controls (HCs). The differences of large-scale brain network functional connectivity (FC) between the four groups were compared and correlated with clinical characteristics. To validate the generalizability of our findings, we recruited a small longitudinal independent sample of BD patients (n = 11). In addition, we examined topological nodal properties across four groups as exploratory analysis.

RESULTS

A specific strengthened pattern of network FC, predominantly involving the default mode network (DMN), was observed in (hypo)manic patients when compared with HCs and bipolar patients in other mood states. Longitudinal observation revealed an increase in several network FCs in patients during (hypo)manic episode. Both samples evidenced an increase in the FC between the DMN and ventral attention network, and between the DMN and limbic network (LN) related to (hypo)mania. The altered network connections were correlated with mania severity and positive affect. Bipolar depressive patients exhibited decreased FC within the LN compared with HCs. The exploratory analysis also revealed an increase in degree in (hypo)manic patients.

CONCLUSIONS

Our findings identify a distributed pattern of large-scale network disturbances in the unique context of (hypo)mania and thus provide new evidence for our understanding of the neural mechanism of BD.

Effects of healthy aging and mnemonic strategies on verbal memory performance across the adult lifespan: Mediating role of posterior hippocampus

In this study, we aimed to understand the contributions of hippocampal anteroposterior subregions (head, body, tail) and subfields (cornu ammonis 1-3 [CA1-3], dentate gyrus [DG], and subiculum [Sub]) and encoding strategies to the age-related verbal memory decline. Healthy participants were administered the California Verbal Learning Test-II to evaluate verbal memory performance and encoding strategies and underwent 4.7 T magnetic resonance imaging brain scan with subsequent hippocampal subregions and subfields manual segmentation. While total hippocampal volume was not associated with verbal memory performance, we found the volumes of the posterior hippocampus (body) and Sub showed significant effects on verbal memory performance. Additionally, the age-related volume decline in hippocampal body volume contributed to lower use of semantic clustering, resulting in lower verbal memory performance. The effect of Sub on verbal memory was statistically independent of encoding strategies. While total CA1-3 and DG volumes did not show direct or indirect effects on verbal memory, exploratory analyses with DG and CA1-3 volumes within the hippocampal body subregion suggested an indirect effect of age-related volumetric reduction on verbal memory performance through semantic clustering. As semantic clustering is sensitive to age-related hippocampal volumetric decline but not to the direct effect of age, further investigation of mechanisms supporting semantic clustering can have implications for early detection of cognitive impairments and decline.

Lateral prefrontal cortex thickness is associated with stress but not cognitive fatigue in exhaustion disorder

Introduction

Impaired executive functioning, including cognitive fatigue, is a core feature of the long-term stress-related condition exhaustion disorder (ED). Recent research suggests that a key area for executive control, the lateral prefrontal cortex (LPFC), may be mechanistically linked to cognitive fatigue due to stress. Here, we therefore asked if and how stress, the LPFC and cognitive fatigue may be related in ED.

Methods

We used a multimodal cross-sectional study design with high-resolution structural magnetic resonance imaging (MRI), self-reported measures, and path analysis modeling in 300 participants with ED.

Results

We found positive associations between stress and cognitive fatigue, and stress and LPFC thickness,but no association between LPFC thickness and cognitive fatigue. Furthermore, LPFC thickness did not mediate or moderate the association between stress and cognitive fatigue.

Discussion

These findings suggest that LPFC brain morphology is related to perceived stress levels but not cognitive fatigue, expanding previous research on the role of the LPFC in executive functioning. Moreover, the results support the notion that the LPFC may be mechanistically involved in stress-related executive function impairment but prompt further research into if and how this may be related to cognitive symptoms in ED.

Age-related differences in associative memory recognition of Chinese characters and hippocampal subfield volumes

Associative memory is a type of hippocampal-dependent episodic memory that declines with age. Studies have examined the neural substrates underlying associative memory and considered the hippocampus holistically; however, the association between associative memory decline and volumetric change in hippocampal subfields in the context of normal aging remains uncharacterized. Leveraging the distinct linguistic features of Chinese characters to evaluate distinct types of false recognition, we investigated age-related differences in associative recognition and hippocampal subfield volumes, as well as the relationship between behavioral performance and hippocampal morphometry in 25 younger adults and 32 older adults. The results showed an age-related associative memory deficit, which was exacerbated after a 30-min delay. Older adults showed higher susceptibility to false alarm errors with recombined and orthographically related foils compared to phonologically or semantically related ones. Moreover, we detected a disproportionately age-related, time-dependent increase in orthographic errors. Older adults exhibited smaller volumes in all hippocampal subfields when compared to younger adults, with a less pronounced effect observed in the CA2/3 subfield. Group-collapsed correlational analyses revealed associations between specific hippocampal subfields and associative memory but not item memory. Additionally, multi-subfield regions had prominent associations with delayed recognition. These findings underscore the significance of multiple hippocampal subfields in various hippocampal-dependent processes including associative memory, recollection-based retrieval, and pattern separation ability. Moreover, our observations of age-related difficulty in differentiating perceptually similar foils from targets provide a unique opportunity for examining the essential contribution of individual hippocampal subfields to the pattern separation process in mnemonic recognition.