Brainwide functional networks associated with anatomically- and functionally-defined hippocampal subfields using ultrahigh-resolution fMRI

Chang, Wei-Tang; Langella, Stephanie; Tang, Yichuan; Ahmad, Sahar; Zhang, Han; Yap, Pew-Thian; Giovanello, Kelly S.; Lin, Weili

doi:10.1038/s41598-021-90364-7

Cited by 4 publications

(4 citation statements)

References 59 publications

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“…The anatomic side of memory is mainly situated in the hippocampus [25]. It is a neural structure with complex efferent and afferent connections with various brain cortices, that exerts a fundamental role in learning [26]. Consequently, STM and LTM are archived mainly in the hippocampus, but also in other cortex regions.…”

Section: Cognitive Functions Memory and Agingmentioning

confidence: 99%

From Exercise to Cognitive Performance: Role of Irisin

et al. 2021

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The beneficial effects of exercise on the brain are well known. In general, exercise offers an effective way to improve cognitive function in all ages, particularly in the elderly, who are considered the most vulnerable to neurodegenerative disorders. In this regard, myokines, hormones secreted by muscle in response to exercise, have recently gained attention as beneficial mediators. Irisin is a novel exercise-induced myokine, that modulates several bodily processes, such as glucose homeostasis, and reduces systemic inflammation. Irisin is cleaved from fibronectin type III domain containing 5 (FNDC5), a transmembrane precursor protein expressed in muscle under the control of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α). The FNDC5/irisin system is also expressed in the hippocampus, where it stimulates the expression of the neurotrophin brain-derived neurotrophic factor in this area that is associated with learning and memory. In this review, we aimed to discuss the role of irisin as a key mediator of the beneficial effects of exercise on synaptic plasticity and memory in the elderly, suggesting its roles within the main promoters of the beneficial effects of exercise on the brain.

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Section: Cognitive Functions Memory and Agingmentioning

confidence: 99%

From Exercise to Cognitive Performance: Role of Irisin

et al. 2021

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“…Recent studies suggest that hippocampal subfields may not be distinct functional units. For instance, Chang et al 72 report that the functional organization within the hippocampus is more intricate than what lamellar anatomical divisions might capture. For one, the posterior and anterior hippocampus may be biased towards pattern separation and completion, respectively.…”

Section: Discussionmentioning

confidence: 99%

Hippocampal subfield associations with memory depend on stimulus modality and retrieval mode

Aumont,

Bussy,

Bedard

et al. 2023

Brain Communications

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Hippocampal atrophy is a well-known feature of age-related memory decline, and hippocampal subfields may contribute differently to this decline. In this cross-sectional study, we investigated the associations between hippocampal subfield volumes and performance in free recall and recognition memory tasks in both verbal and visual modalities in older adults without dementia. We collected MRIs from 97 (41 males) right-handed participants aged over 60. We segmented the right and left hippocampi into 1) dentate gyrus and cornu ammonis 4 (DG/CA4); 2) CA2 and CA3 (CA2/CA3); 3) CA1; 4) strata radiatum, lacunosum and moleculare (SRLM); and 5) subiculum. Memory was assessed with verbal free recall and recognition tasks, as well as visual free recall and recognition tasks. Amyloid-β and hippocampal tau positivity were assessed using [18F]AZD4694 and [18F]MK6240 PET tracers, respectively. The verbal free recall and verbal recognition performances were positively associated with CA1 and SRLM volumes. The verbal free recall and visual free recall were positively correlated with the right DG/CA4. The visual free recall, but not verbal free recall, was also associated with the right CA2/CA3. The visual recognition was not significantly associated with any subfield volume. Hippocampal tau positivity, but not amyloid-β positivity, was associated with reduced DG/CA4, CA2/CA3 and SRLM volumes. Our results suggest that memory performances are linked to specific subfields. CA1 appears to contribute to the verbal modality, irrespective of the free recall or recognition mode of retrieval. In contrast, DG/CA4 seems to be involved in the free recall mode, irrespective of verbal or visual modalities. These results are concordant with the view that DG/CA4 plays a primary role in encoding a stimulus’ distinctive attributes, and that CA2/CA3 could be instrumental in recollecting a visual memory from one of its fragments. Overall, we show that hippocampal subfield segmentation can be useful for detecting early volume changes and improve our understanding of the hippocampal subfields’ roles in memory.

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“…The hippocampus exhibits cytoarchitectural differences among subfields [14], which may lead to functional distinctions across them. Connectomic and neurophysiological studies have shown differences in the regions they connect to and the directions of connections [15,16]. These differences may be due to genetic determinants, as hippocampal subfields have unique genetic correlates that associate with specific biological processes [17,18].…”

Section: Introductionmentioning

confidence: 99%

Revealing complexity: Segmentation of hippocampal subfields in adolescents with major depressive disorder reveals specific links to cognitive dysfunctions

Zhang,

Liu,

Yang

et al. 2024

Eur. Psychiatr.

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BackgroundHippocampal disruptions represent potential neuropathological biomarkers in depressed adolescents with cognitive dysfunctions. Given heterogeneous outcomes of whole-hippocampus analyses, we investigated subregional abnormalities in depressed adolescents, and their associations with symptom severity and cognitive dysfunctions. MethodsSeventy-nine first-episode depressive patients (age = 15.54±1.83) and seventy-one healthy controls (age = 16.18±2.85) were included. All participants underwent T1 and T2 weighted imaging, completed depressive severity assessments and performed cognitive assessments on memory, emotional recognition, cognitive control, and attention abilities. Freesurfer v6.0 was used to segment each hippocampus into 12 subfields. Multivariable analyses of variance were performed to identify overall and disease severity related abnormalities in patients. LASSO regression was also conducted to explore the associations between hippocampal subfields and cognitive abilities in patients. ResultsDepressed adolescents showed decreases in the dentate gyrus, CA1, CA2/3, CA4, fimbria, tail, and molecular layer. Analyses of overall symptom severity, duration, selfharm behaviour and suicidality suggested that severity-related decreases mainly manifested in CA regions and involved surrounding subfields with disease severity increases. LASSO regression indicated that hippocampal subfields abnormalities had strongest associations with memory impairments, with CA regions and dentate gyrus showing highest weights. ConclusionsHippocampal abnormalities are widespread in depressed adolescents and such abnormalities may spread from CA regions to surrounding areas with the disease progresses. Abnormalities in CA regions and dentate gyrus among these subfields primarily link with memory impairments in patients. These results demonstrate that hippocampal subsections may serve as useful biomarkers of depression progression in adolescents, offering new directions for early clinical intervention.

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Brainwide functional networks associated with anatomically- and functionally-defined hippocampal subfields using ultrahigh-resolution fMRI

Cited by 4 publications

References 59 publications

From Exercise to Cognitive Performance: Role of Irisin

From Exercise to Cognitive Performance: Role of Irisin

Hippocampal subfield associations with memory depend on stimulus modality and retrieval mode

Revealing complexity: Segmentation of hippocampal subfields in adolescents with major depressive disorder reveals specific links to cognitive dysfunctions

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