Hippocampus in health and disease: An overview

Sparing the Hippocampus in Prophylactic Cranial Irradiation Using Three Different Linear Accelerators: A Comparative Study

Hippocampus protection, as an organ at risk in brain radiotherapy, might protect patients' quality of life. Prophylactic cranial irradiation (PCI) has been used traditionally in small cell lung cancer (SCLC) patients as it increases survival. This study aimed to discover the contributing parameters for a successful PCI with simultaneous protection of the hippocampus by using three different treatment machines. For this purpose, treatment plans were generated for 45 SCLC patients using three half-arcs in three linear accelerators (LINACs; Elekta Infinity, Synergy, and Axesse; Elekta Ltd, Stockholm, Sweden) with different radiation field sizes and multileaf collimator (MLC) leaf thickness characteristics. The prescribed dose was 25 Gy in 10 fractions. Thresholds for the hippocampus were calculated based on the Radiation Therapy Oncology Group 0933 dose constraints. The planning and treatment system templates were common to all three LINACs. Plan evaluation was based on the dosimetric target coverage by the 95% isodose, the maximum dose of the plan, the conformity index (CI), the degree of plan modulation (MOD), and the patient-specific quality assurance (QA) pass rate. The mean target coverage was highest for Infinity (97.3%), followed by Axesse (96.6%) and Synergy (95.5%). The mean maximum dose was higher for Synergy (27.5 Gy), followed by Infinity (27.0 Gy) and Axesse (26.9 Gy). Axesse plans had the highest CI (0.93), followed by Infinity (0.91) and Synergy (0.88). Plan MOD was lower for Synergy (2.88) compared with Infinity (3.07) and Axesse (3.69). Finally, patient-specific QA was successful in all Infinity plans, in all but one Synergy plan, and in 17/45 Axesse plans, as was expected from the field size in that treatment unit. Based on overall performance, the most favorable combination of target coverage, hippocampus sparing, and plan deliverability was obtained with the LINAC, which has the largest field opening and thinnest MLC leaves.

Fine hippocampal morphology analysis with a multi-dataset cross-sectional study on 2911 subjects

CA1 subfield and subiculum of the hippocampus contain a series of dentate bulges, which are also called hippocampus dentation (HD). There have been several studies demonstrating an association between HD and brain disorders. Such as the number of hippocampal dentation correlates with temporal lobe epilepsy. And epileptic hippocampus have a lower number of dentation compared to contralateral hippocampus. However, most studies rely on subjective assessment by manual searching and counting in HD areas, which is time-consuming and labor-intensive to process large amounts of samples. And to date, only one objective method for quantifying HD has been proposed. Therefore, to fill this gap, we developed an automated and objective method to quantify HD and explore its relationship with neurodegenerative diseases. In this work, we performed a fine-scale morphological characterization of HD in 2911 subjects from four different cohorts of ADNI, PPMI, HCP, and IXI to quantify and explore differences between them in MR T1w images. The results showed that the degree of right hippocampal dentation are lower in patients with Alzheimer's disease than samples in mild cognitive impairment or cognitively normal, whereas this change is not significant in Parkinson's disease progression. The innovation of this paper that we propose a quantitative, robust, and fully automated method. These methodological innovation and corresponding results delineated above constitute the significance and novelty of our study. What's more, the proposed method breaks through the limitations of manual labeling and is the first to quantitatively measure and compare HD in four different brain populations including thousands of subjects. These findings revealed new morphological patterns in the hippocampal dentation, which can help with subsequent fine-scale hippocampal morphology research.

Neuroprotective Role of Selenium Nanoparticles Against Behavioral, Neurobiochemical and Histological Alterations in Rats Subjected to Chronic Restraint Stress

Chronic stress induces changes in the prefrontal cortex and hippocampus. Selenium nanoparticles (SeNPs) showed promising results in several neurological animal models. The implementation of SeNPs in chronic restraint stress (CRS) remains to be elucidated. This study was done to determine the possible protective effects of selenium nanoparticles on behavioral changes and brain oxidative stress markers in a rat model of CRS. 50 rats were divided into three groups; control group (n = 10), untreated CRS group (n = 10) and CRS-SeNPs treated group (n = 30). Restraint stress was performed 6 h./day for 21 days. Rats of CRS-SeNPs treated group received 1, 2.5 or 5 mg/kg SeNPs (10 rats each) by oral gavage for 21 days. Rats were subjected to behavioral assessments and then sacrificed for biochemical and histological analysis of the prefrontal cortex and hippocampus. Prefrontal cortical and hippocampal serotonin levels, oxidative stress markers including malondialdehyde (MDA), reduced glutathione (GSH) and glutathione peroxidase (GPx), tumor necrosis factor alpha (TNF-α) and caspase-3 were assessed. Accordingly, different doses of SeNPs showed variable effectiveness in ameliorating disease parameters, with 2.5 mg/kg dose of SeNPs showing the best improving results in all studied parameters. The present study exhibited the neuroprotective role of SeNPs in rats subjected to CRS and proposed their antioxidant, anti-inflammatory and anti-apoptotic effects as the possible mechanism for increased prefrontal cortical and hippocampal serotonin level, ameliorated anxiety-like and depressive-like behaviors and improved prefrontal cortical and hippocampal histological architecture.

Melatonin is a Neuroprotective and Antioxidant Agent against Neurotoxicity Induced by an Intrahippocampal Injection of Nickel in Rats

The investigation into the hippocampal function and its response to heavy metal exposure is crucial for understanding the mechanisms underlying neurotoxicity, this can potentially inform strategies for mitigating the adverse effects associated with heavy metal exposure. Melatonin is an essential neuromodulator known for its efficacy as an antioxidant. In this study, we aimed to determine whether melatonin could protect against Nickel (Ni) neurotoxicity. To achieve this, we performed an intracerebral injection of Ni (300 µM NiCl2) into the right hippocampus of male Wistar rats, followed by melatonin treatment. Based on neurobehavioral and neurobiochemical assessments, our results demonstrate that melatonin efficiently enhances Ni-induced behavioral dysfunction and cognitive impairment. Specifically, melatonin treatment positively influences anxious behavior, significantly reduces immobility time in the forced swim test (FST), and improves learning and spatial memory abilities. Moreover, neurobiochemical assays revealed that melatonin treatment modulates the Ni-induced alterations in oxidative stress balance by increasing antioxidant enzyme activities, such as superoxide dismutase (SOD) and catalase (CAT). Additionally, we observed that melatonin significantly attenuated the increased levels of lipid peroxidation (LPO) and nitric oxide (NO). In conclusion, the data from this study suggests that melatonin attenuates oxidative stress, which is the primary mechanism responsible for Ni-induced neurotoxicity. Considering that the hippocampus is the main structure involved in the pathology associated with heavy metal intoxication, such as Ni, these findings underscore the potential therapeutic efficacy of melatonin in mitigating heavy metal-induced brain damage.

Prenatal delivery of a therapeutic antisense oligonucleotide achieves broad biodistribution in the brain and ameliorates Angelman syndrome phenotype in mice

Angelman syndrome (AS), an early-onset neurodevelopmental disorder characterized by abnormal gait, intellectual disabilities, and seizures, occurs when the maternal allele of the UBE3A gene is disrupted, since the paternal allele is silenced in neurons by the UBE3A antisense (UBE3A-AS) transcript. Given the importance of early treatment, we hypothesized that prenatal delivery of an antisense oligonucleotide (ASO) would downregulate the murine Ube3a-AS, resulting in increased UBE3A protein and functional rescue. Using a mouse model with a Ube3a-YFP allele that reports on-target ASO activity, we found that in utero, intracranial (IC) injection of the ASO resulted in dose-dependent activation of paternal Ube3a, with broad biodistribution. Accordingly, in utero injection of the ASO in a mouse model of AS also resulted in successful restoration of UBE3A and phenotypic improvements in treated mice on the accelerating rotarod and fear conditioning. Strikingly, even intra-amniotic (IA) injection resulted in systemic biodistribution and high levels of UBE3A reactivation throughout the brain. These findings offer a novel strategy for early treatment of AS using an ASO, with two potential routes of administration in the prenatal window. Beyond AS, successful delivery of a therapeutic ASO into neurons has implications for a clinically feasible prenatal treatment for numerous neurodevelopmental disorders.

The Role of PET Imaging in Patients with Prion Disease: A Literature Review

Prion diseases are rare, rapidly progressive, and fatal incurable degenerative brain disorders caused by the misfolding of a normal protein called PrPC into an abnormal protein called PrPSc. Their highly variable clinical presentation mimics various degenerative and non-degenerative brain disorders, making diagnosis a significant challenge for neurologists. Currently, definitive diagnosis relies on post-mortem examination of nervous tissue to detect the pathogenic prion protein. The current diagnostic criteria are limited. While structural magnetic resonance imaging (MRI) remains the gold standard imaging modality for Creutzfeldt-Jakob disease (CJD) diagnosis, positron emission tomography (PET) using 18fluorine-fluorodeoxyglucose (18F-FDG) and other radiotracers have demonstrated promising potential in the diagnostic assessment of prion disease. In this context, a comprehensive and updated review exclusively focused on PET imaging in prion diseases is still lacking. We review the current value of PET imaging with 18F-FDG and non-FDG tracers in the diagnostic management of prion diseases. From the collected data, 18F-FDG PET mainly reveals cortical and subcortical hypometabolic areas in prion disease, although fails to identify typical pattern or laterality abnormalities to differentiate between genetic and sporadic prion diseases. Although the rarity of prion diseases limits the establishment of a definitive hypometabolism pattern, this review reveals some more prevalent 18F-FDG patterns associated with each disease subtype. Interestingly, in both sporadic and genetic prion diseases, the hippocampus does not show significant glucose metabolism alterations, appearing as a useful sign in the differential diagnosis with other neurodegenerative disease. In genetic prion disease forms, PET abnormality precedes clinical manifestation. Discordant diagnostic value for amyloid tracers among different prion disease subtypes was observed, needing further investigation. PET has emerged as a potential valuable tool in the diagnostic armamentarium for CJD. Its ability to visualize functional and metabolic brain changes provides complementary information to structural MRI, aiding in the early detection and confirmation of CJD.

Analysis of the cognitive and functional behavior of female rats in the periestropause after hormone therapy with estrogen

Perimenopause is a critical period, with severe cycle irregularity and lower estrogen secretion altering redox state biomarkers, leading to behavioral changes. The estrogen hormonal therapy (EHT) being commonly used to alleviate climacteric effects. Therefore, the aim of this study was to analyze anxiolytic profile, recognition memory (short and long term), ambulation, redox status, cell synaptic activity in locus coeruleus and hippocampus of Wistar rats in the periestropause after EHT. Forty rats participated in the study; 20 were treated with corn oil (group 21Mo/Veh; corn oil/0.2 mL/sc; 2x/week) and 20 were submitted to EHT (group 21Mo/E2; 17β-estradiol/15 μg/Kg/sc; 2x/week) for 120 days. Open field, elevated plus maze, object recognition (RO), and footprint tests were performed immediately before and at the end of the treatment period. From the decapitated brains, isolated hippocampus were destined for biochemical analysis, in turn, perfused brains were destined for histological analysis. The 21Mo/E2 group had a significantly greater total time in the central region and a significantly greater number of entries into the open arms compared to the 21Mo/Veh group, as in crossing, rearing and grooming behaviors, evidencing an anxiolytic profile. In the RO test, the 21Mo/Veh group decreased long-term memory, and the 21Mo/E2 group maintained the same index as at 17 months of age, in addition to a better balance of the hippocampal redox state, prevention of neuronal cell loss and better gait. Based on the results, it appears that exogenous E2 supplementation during periestropause may help preserve neurological functions and potentially prevent neuropsychological and neurodegenerative disorders.

Effect of chemotherapy on hippocampal volume and shape in older long-term breast cancer survivors

Purpose

The objective of this study was to assess changes in hippocampal volume and shape in older long-term breast cancer survivors who were exposed to chemotherapy 5-15 years prior.

Methods

This study recruited female long-term breast cancer survivors aged 65 years or older with a history of chemotherapy (C+), age-matched breast cancer survivors who did not receive chemotherapy (C-), and healthy controls (HC). The participants were recruited 5-15 years after chemotherapy at time point 1 (TP1) and were followed up for 2 years at time point 2 (TP2). Assessments included hippocampal volume and shape from brain MRI scans and neuropsychological (NP) tests.

Results

At TP1, each of the three groups was comprised of 20 participants. The C+ group exhibited a hippocampal volume loss estimated in proportion with total intracranial volume (ICV) in both the left and right hemispheres from TP1 to TP2. Regarding the hippocampal shape at TP1, the C+ group displayed inward changes compared to the control groups. Within the C+ group, changes in right hippocampal volume adjusted with ICV were positively correlated with crystalized composite scores (R = 0.450, p = 0.044). Additionally, in C+ groups, chronological age was negatively correlated with right hippocampal volume adjusted with ICV (R = -0.585, p = 0.007).

Conclusion

The observed hippocampal volume reduction and inward shape deformation within the C+ group may serve as neural basis for cognitive changes in older long-term breast cancer survivors with history of chemotherapy treatment.

Neurodegenerative effects of air pollutant Particles: Biological mechanisms implicated for Early-Onset Alzheimer's disease

BACKGROUND

Sporadic Alzheimer's disease (AD) occurs in 99% of all cases and can be influenced by air pollution such as diesel emissions and more recently, an iron oxide particle, magnetite, detected in the brains of AD patients. However, a mechanistic link between air pollutants and AD development remains elusive.

AIM

To study the development of AD-relevant pathological effects induced by air pollutant particle exposures and their mechanistic links, in wild-type and AD-predisposed models.

METHODS

C57BL/6 (n = 37) and APP/PS1 transgenic (n = 38) mice (age 13 weeks) were exposed to model pollutant iron-based particle (Fe0-Fe3O4, dTEM = 493 ± 133 nm), hydrocarbon-based diesel combustion particle (43 ± 9 nm) and magnetite (Fe3O4, 153 ± 43 nm) particles (66 µg/20 µL/third day) for 4 months, and were assessed for behavioural changes, neuronal cell loss, amyloid-beta (Aβ) plaque, immune response and oxidative stress-biomarkers. Neuroblastoma SHSY5Y (differentiated) cells were exposed to the particles (100 μg/ml) for 24 h, with assessments on immune response biomarkers and reactive oxygen species generation.

RESULTS

Pollutant particle-exposure led to increased anxiety and stress levels in wild-type mice and short-term memory impairment in AD-prone mice. Neuronal cell loss was shown in the hippocampal and somatosensory cortex, with increased detection of Aβ plaque, the latter only in the AD-predisposed mice, with the wild-type not genetically disposed to form the plaque. The particle exposures however, increased AD-relevant immune system responses, including inflammation, in both strains of mice. Exposures also stimulated oxidative stress, although only observed in wild-type mice. The in vitro studies complemented the immune response and oxidative stress observations.

CONCLUSIONS

This study provides insights into the mechanistic links between inflammation and oxidative stress to pollutant particle-induced AD pathologies, with magnetite apparently inducing the most pathological effects. No exacerbation of the effects was observed in the AD-predisposed model when compared to the wild-type, indicating a particle-induced neurodegeneration that is independent of disease state.

Hippocampal functional connectivity mediates the association between cardiorespiratory fitness and cognitive function in healthy young adults

OBJECTIVE

Higher cardiorespiratory fitness (CRF) induces neuroprotective effects in the hippocampus, a key brain region for memory and learning. We investigated the association between CRF and functional connectivity (FC) of the hippocampus in healthy young adults. We also examined the association between hippocampal FC and neurocognitive function. Lastly, we tested whether hippocampal FC mediates the association between 2-Min Walk Test (2MWT) and neurocognitive function.

METHODS

913 young adults (28.7 ± 3.7 years) from the Human Connectome Project were included in the analyses. The 2MWT performance result was used as a proxy for cardiovascular endurance. Fluid and crystalized composite neurocognitive scores were used to assess cognition. Resting-state functional MRI data were processed to measure hippocampal FC. Linear regression was used to examine the association between 2MWT, hippocampal FC, and neurocognitive outcomes after controlling for age, sex, years of education, body mass index, systolic blood pressure, and gait speed.

RESULTS

Better 2MWT performance was associated with greater FC between the anterior hippocampus and right posterior cingulate and left middle temporal gyrus. No associations between 2MWT and posterior hippocampal FC, whole hippocampal FC, and caudate FC (control region) were observed. Greater anterior hippocampal FC was associated with better crystalized cognition scores. Lastly, greater FC between the anterior hippocampus and right posterior cingulate mediated the association between better 2MWT scores and higher crystalized cognition scores.

CONCLUSIONS

Anterior hippocampal FC may be one underlying neurophysiological mechanism that promotes the association between 2MWT performance and crystalized composite cognitive function in healthy young adults.

Concomitant administration of resveratrol and resistance training ameliorates acrylamide-induced spatial learning impairment in rats

Objective

The present study examined effects of resistance training (RT) and resveratrol (RES) alone and together on acrylamide (AC)-induced memory impairment in rats.

Materials and Methods

Animals were divided into 6 groups: (1) Control group which received normal saline intraperitoneally (ip) daily for 8 weeks; (2) Scopolamine (SCO) group which received SCO (1 mg/kg/day, ip) for 8 weeks; (3) AC group which received AC (5 mg/kg/day, ip) for 8 weeks; (4) AC + RT group which received AC (5 mg/kg/day, ip) for 8 weeks and performed RT (5 days a week for 8 weeks); (5) AC + RES group which received AC (5 mg/kg/day, ip) and RES (1 mg/kg/day, ip) for 8 weeks; and (6) AC + RT + RES group which received AC (5 mg/kg/day, ip) and RES (1 mg/kg/day, ip) for 8 weeks and performed RT (5 days a week for 8 weeks). On day 53, animal training began in the Morris Water Maze (MWM) and 24 hr after the last training, the probe test was performed.

Results

RT and RES alone did not significantly affect escape latency or traveled distance increased by AC. However, concomitant RES and RT treatment significantly reduced these parameters compared to the AC group. Co-treatment with RES and RT also significantly increased the time spent in the target quadrant compared to the AC group. Lipid peroxidation was reduced in the AC+RES and AC+RT+RES groups compared to the AC group.

Conclusion

It seems that daily co-treatment with RES and RT for 8 weeks ameliorates the memory-impairing effects of AC.

Vulnerability of the Hippocampus to Insults: Links to Blood-Brain Barrier Dysfunction

The hippocampus is a critical brain substrate for learning and memory; events that harm the hippocampus can seriously impair mental and behavioral functioning. Hippocampal pathophysiologies have been identified as potential causes and effects of a remarkably diverse array of medical diseases, psychological disorders, and environmental sources of damage. It may be that the hippocampus is more vulnerable than other brain areas to insults that are related to these conditions. One purpose of this review is to assess the vulnerability of the hippocampus to the most prevalent types of insults in multiple biomedical domains (i.e., neuroactive pathogens, neurotoxins, neurological conditions, trauma, aging, neurodegenerative disease, acquired brain injury, mental health conditions, endocrine disorders, developmental disabilities, nutrition) and to evaluate whether these insults affect the hippocampus first and more prominently compared to other brain loci. A second purpose is to consider the role of hippocampal blood-brain barrier (BBB) breakdown in either causing or worsening the harmful effects of each insult. Recent research suggests that the hippocampal BBB is more fragile compared to other brain areas and may also be more prone to the disruption of the transport mechanisms that act to maintain the internal milieu. Moreover, a compromised BBB could be a factor that is common to many different types of insults. Our analysis indicates that the hippocampus is more vulnerable to insults compared to other parts of the brain, and that developing interventions that protect the hippocampal BBB may help to prevent or ameliorate the harmful effects of many insults on memory and cognition.

MRI biomarkers and neuropsychological assessments of hippocampal and parahippocampal regions affected by ALS: A systematic review

BACKGROUND AND OBJECTIVE

Amyotrophic lateral sclerosis (ALS) is a progressive motor and extra-motor neurodegenerative disease. This systematic review aimed to examine MRI biomarkers and neuropsychological assessments of the hippocampal and parahippocampal regions in patients with ALS.

METHODS

A systematic review was conducted in the Scopus and PubMed databases for studies published between January 2000 and July 2023. The inclusion criteria were (1) MRI studies to assess hippocampal and parahippocampal regions in ALS patients, and (2) studies reporting neuropsychological data in patients with ALS.

RESULTS

A total of 46 studies were included. Structural MRI revealed hippocampal atrophy, especially in ALS-FTD, involving specific subregions (CA1, dentate gyrus). Disease progression and genetic factors impacted atrophy patterns. Diffusion tensor imaging (DTI) showed increased mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), and decreased fractional anisotropy (FA) in the hippocampal tracts and adjacent regions, indicating loss of neuronal and white matter integrity. Functional MRI (fMRI) revealed reduced functional connectivity (FC) between the hippocampus, parahippocampus, and other regions, suggesting disrupted networks. Perfusion MRI showed hypoperfusion in parahippocampal gyri. Magnetic resonance spectroscopy (MRS) found changes in the hippocampus, indicating neuronal loss. Neuropsychological tests showed associations between poorer memory and hippocampal atrophy or connectivity changes. CA1-2, dentate gyrus, and fimbria atrophy were correlated with worse memory.

CONCLUSIONS

The hippocampus and the connected regions are involved in ALS. Hippocampal atrophy disrupted connectivity and metabolite changes correlate with cognitive and functional decline. Specific subregions can be particularly affected. The hippocampus is a potential biomarker for disease monitoring and prognosis.

Improving brain age prediction with anatomical feature attention-enhanced 3D-CNN

Currently, significant progress has been made in predicting brain age from structural Magnetic Resonance Imaging (sMRI) data using deep learning techniques. However, despite the valuable structural information they contain, the traditional engineering features known as anatomical features have been largely overlooked in this context. To address this issue, we propose an attention-based network design that integrates anatomical and deep convolutional features, leveraging an anatomical feature attention (AFA) module to effectively capture salient anatomical features. In addition, we introduce a fully convolutional network, which simplifies the extraction of deep convolutional features and overcomes the high computational memory requirements associated with deep learning. Our approach outperforms several widely-used models on eight publicly available datasets (n = 2501), with a mean absolute error (MAE) of 2.20 years in predicting brain age. Comparisons with deep learning models lacking the AFA module demonstrate that our fusion model effectively improves overall performance. These findings provide a promising approach for combining anatomical and deep convolutional features from sMRI data to predict brain age, with potential applications in clinical diagnosis and treatment, particularly for populations with age-related cognitive decline or neurological disorders.

Advancing Beyond the Hippocampus to Preserve Cognition for Patients With Brain Metastases: Dosimetric Results From a Phase 2 Trial of Memory-Avoidance Whole Brain Radiation Therapy

Purpose

Recent advances to preserve neurocognitive function in patients treated for brain metastases include stereotactic radiosurgery, hippocampal avoidance whole brain radiation therapy (WBRT), and memantine administration. The hippocampus, corpus callosum, fornix, and amygdala are key neurocognitive substructures with a low propensity for brain metastases. Herein, we report our preliminary experience using a "memory-avoidance" WBRT (MA-WBRT) approach that spares these substructures for patients with >15 brain metastases.

Methods and Materials

Ten consecutive patients treated with MA-WBRT on a phase 2 clinical trial were reviewed. In each patient, the hippocampi, amygdalae, corpus callosum, and fornix were contoured. Patients were not eligible for MA-WBRT if they had metastases in these substructures. A memory-avoidance region was created using a 5-mm volumetric expansion around these substructures. Hotspots were avoided in the hypothalamus and pituitary gland. Coverage of brain metastases was prioritized over memory avoidance dose constraints. Dose constraints for these avoidance structures included a D100% ≤ 9 Gy and D0.03 cm3 ≤ 16 Gy (variation acceptable to 20 Gy). LINAC-based volumetric modulated arc therapy plans were generated for a prescription dose of 30 Gy in 10 fractions.

Results

On average, the memory avoidance structure volume was 37.1 cm3 (range, 25.2-44.6 cm3), occupying 2.5% of the entire whole brain target volume. All treatment plans met the D100% dose constraint, and 8 of 10 plans met the D0.03 cm3 constraint, with priority given to tumor coverage for the remaining 2 cases. Target coverage (D98% > 25 Gy) and homogeneity (D2% ≤ 37.5 Gy) were achieved for all plans.

Conclusions

Modern volumetric modulated arc therapy techniques allow for sparing of the hippocampus, amygdala, corpus callosum, and fornix with good target coverage and homogeneity. After enrollment is completed, quality of life and cognitive data will be evaluated to assess the efficacy of MA-WBRT to mitigate declines in quality of life and cognition after whole brain radiation.

Exploring the interplay between running exercises, microbial diversity, and tryptophan metabolism along the microbiota-gut-brain axis

The emergent recognition of the gut-brain axis connection has shed light on the role of the microbiota in modulating the gut-brain axis's functions. Several microbial metabolites, such as serotonin, kynurenine, tryptamine, indole, and their derivatives originating from tryptophan metabolism have been implicated in influencing this axis. In our study, we aimed to investigate the impact of running exercises on microbial tryptophan metabolism using a mouse model. We conducted a multi-omics analysis to obtain a comprehensive insight into the changes in tryptophan metabolism along the microbiota-gut-brain axis induced by running exercises. The analyses integrated multiple components, such as tryptophan changes and metabolite levels in the gut, blood, hippocampus, and brainstem. Fecal microbiota analysis aimed to examine the composition and diversity of the gut microbiota, and taxon-function analysis explored the associations between specific microbial taxa and functional activities in tryptophan metabolism. Our findings revealed significant alterations in tryptophan metabolism across multiple sites, including the gut, blood, hippocampus, and brainstem. The outcomes indicate a shift in microbiota diversity and tryptophan metabolizing capabilities within the running group, linked to increased tryptophan transportation to the hippocampus and brainstem through circulation. Moreover, the symbiotic association between Romboutsia and A. muciniphila indicated their potential contribution to modifying the gut microenvironment and influencing tryptophan transport to the hippocampus and brainstem. These findings have potential applications for developing microbiota-based approaches in the context of exercise for neurological diseases, especially on mental health and overall well-being.

Comparative Hippocampal Proteome and Phosphoproteome in a Niemann-Pick, Type C1 Mouse Model Reveal Insights into Disease Mechanisms

Niemann-Pick disease, type C (NPC) is a neurodegenerative, lysosomal storage disorder in individuals carrying two mutated copies of either the NPC1 or NPC2 gene. Consequently, impaired cholesterol recycling and an array of downstream events occur. Interestingly, in NPC, the hippocampus displays lysosomal lipid storage but does not succumb to progressive neurodegeneration as significantly as other brain regions. Since defining the neurodegeneration mechanisms in this disease is still an active area of research, we use mass spectrometry to analyze the overall proteome and phosphorylation pattern changes in the hippocampal region of a murine model of NPC. Using 3 week old mice representing an early disease time point, we observed changes in the expression of 47 proteins, many of which are consistent with the previous literature. New to this study, changes in members of the SNARE complex, including STX7, VTI1B, and VAMP7, were identified. Furthermore, we identified that phosphorylation of T286 on CaMKIIα and S1303 on NR2B increased in mutant animals, even at the late stage of the disease. These phosphosites are crucial to learning and memory and can trigger neuronal death by altering protein-protein interactions.

Exploring the complexities of 1C metabolism: implications in aging and neurodegenerative diseases

The intricate interplay of one-carbon metabolism (OCM) with various cellular processes has garnered substantial attention due to its fundamental implications in several biological processes. OCM serves as a pivotal hub for methyl group donation in vital biochemical reactions, influencing DNA methylation, protein synthesis, and redox balance. In the context of aging, OCM dysregulation can contribute to epigenetic modifications and aberrant redox states, accentuating cellular senescence and age-associated pathologies. Furthermore, OCM's intricate involvement in cancer progression is evident through its capacity to provide essential one-carbon units crucial for nucleotide synthesis and DNA methylation, thereby fueling uncontrolled cell proliferation and tumor development. In neurodegenerative disorders like Alzheimer's and Parkinson's, perturbations in OCM pathways are implicated in the dysregulation of neurotransmitter synthesis and mitochondrial dysfunction, contributing to disease pathophysiology. This review underscores the profound impact of OCM in diverse disease contexts, reinforcing the need for a comprehensive understanding of its molecular complexities to pave the way for targeted therapeutic interventions across inflammation, aging and neurodegenerative disorders.

An imaging review of the hippocampus and its common pathologies

The hippocampus is a complex structure located in the mesial temporal lobe that plays a critical role in cognitive and memory-related processes. The hippocampal formation consists of the dentate gyrus, hippocampus proper, and subiculum, and its importance in the neural circuitry makes it a key anatomic structure to evaluate in neuroimaging studies. Advancements in imaging techniques now allow detailed assessment of hippocampus internal architecture and signal features that has improved identification and characterization of hippocampal abnormalities. This review aims to summarize the neuroimaging features of the hippocampus and its common pathologies. It provides an overview of the hippocampal anatomy on magnetic resonance imaging and discusses how various imaging techniques can be used to assess the hippocampus. The review explores neuroimaging findings related to hippocampal variants (incomplete hippocampal inversion, sulcal remnant and choroidal fissure cysts), and pathologies of neoplastic (astrocytoma and glioma, ganglioglioma, dysembryoplastic neuroepithelial tumor, multinodular and vacuolating neuronal tumor, and metastasis), epileptic (mesial temporal sclerosis and focal cortical dysplasia), neurodegenerative (Alzheimer's disease, progressive primary aphasia, and frontotemporal dementia), infectious (Herpes simplex virus and limbic encephalitis), vascular (ischemic stroke, arteriovenous malformation, and cerebral cavernous malformations), and toxic-metabolic (transient global amnesia and opioid-associated amnestic syndrome) etiologies.

A Review of the Common Neurodegenerative Disorders: Current Therapeutic Approaches and the Potential Role of Bioactive Peptides

Neurodegenerative disorders, which include Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS), represent a significant and growing global health challenge. Current therapies predominantly focus on symptom management rather than altering disease progression. In this review, we discuss the major therapeutic strategies in practice for these disorders, highlighting their limitations. For AD, the mainstay treatments are cholinesterase inhibitors and N-methyl-D-aspartate (NMDA) receptor antagonists. For PD, dopamine replacement therapies, including levodopa, are commonly used. HD is managed primarily with symptomatic treatments, and reusable extends survival in ALS. However, none of these therapies halts or substantially slows the neurodegenerative process. In contrast, this review highlights emerging research into bioactive peptides as potential therapeutic agents. These naturally occurring or synthetically designed molecules can interact with specific cellular targets, potentially modulating disease processes. Preclinical studies suggest that bioactive peptides may mitigate oxidative stress, inflammation, and protein misfolding, which are common pathological features in neurodegenerative diseases. Clinical trials using bioactive peptides for neurodegeneration are limited but show promising initial results. For instance, hemiacetal, a γ-secretase inhibitor peptide, has shown potential in AD by reducing amyloid-beta production, though its development was discontinued due to side effects. Despite these advancements, many challenges remain, including identifying optimal peptides, confirming their mechanisms of action, and overcoming obstacles related to their delivery to the brain. Future research should prioritize the discovery and development of novel bioactive peptides and improve our understanding of their pharmacokinetics and pharmacodynamics. Ultimately, this approach may lead to more effective therapies for neurodegenerative disorders, moving beyond symptom management to potentially modify the course of these devastating diseases.

Traumatic Brain Injury-Induced Fear Generalization in Mice Involves Hippocampal Memory Trace Dysfunction and Is Alleviated by (R,S)-Ketamine

BACKGROUND

Traumatic brain injury (TBI) is a debilitating neurological disorder caused by an impact to the head by an outside force. TBI results in persistent cognitive impairments, including fear generalization and the inability to distinguish between aversive and neutral stimuli. The mechanisms underlying fear generalization have not been fully elucidated, and there are no targeted therapeutics to alleviate this symptom of TBI.

METHODS

To identify the neural ensembles mediating fear generalization, we utilized ArcCreERT2 × enhanced yellow fluorescent protein (EYFP) mice, which allow for activity-dependent labeling and quantification of memory traces. Mice were administered a sham surgery or the controlled cortical impact model of TBI. Mice were then administered a contextual fear discrimination paradigm and memory traces were quantified in numerous brain regions. In a separate group of mice, we tested if (R,S)-ketamine could decrease fear generalization and alter the corresponding memory traces in TBI mice.

RESULTS

TBI mice exhibited increased fear generalization when compared with sham mice. This behavioral phenotype was paralleled by altered memory traces in the dentate gyrus, CA3, and amygdala, but not by alterations in inflammation or sleep. In TBI mice, (R,S)-ketamine facilitated fear discrimination, and this behavioral improvement was reflected in dentate gyrus memory trace activity.

CONCLUSIONS

These data show that TBI induces fear generalization by altering fear memory traces and that this deficit can be improved with a single injection of (R,S)-ketamine. This work enhances our understanding of the neural basis of TBI-induced fear generalization and reveals potential therapeutic avenues for alleviating this symptom.

Automatic cell-type harmonization and integration across Human Cell Atlas datasets

Harmonizing cell types across the single-cell community and assembling them into a common framework is central to building a standardized Human Cell Atlas. Here, we present CellHint, a predictive clustering tree-based tool to resolve cell-type differences in annotation resolution and technical biases across datasets. CellHint accurately quantifies cell-cell transcriptomic similarities and places cell types into a relationship graph that hierarchically defines shared and unique cell subtypes. Application to multiple immune datasets recapitulates expert-curated annotations. CellHint also reveals underexplored relationships between healthy and diseased lung cell states in eight diseases. Furthermore, we present a workflow for fast cross-dataset integration guided by harmonized cell types and cell hierarchy, which uncovers underappreciated cell types in adult human hippocampus. Finally, we apply CellHint to 12 tissues from 38 datasets, providing a deeply curated cross-tissue database with ∼3.7 million cells and various machine learning models for automatic cell annotation across human tissues.

Involvement of estrogen receptor activation in kaempferol-3-O-glucoside's protection against aging-related cognition impairment and microglial inflammation

Estrogens have been demonstrated to inhibit age-related cognitive decline via binding to estrogen receptors (ERs). As a natural flavonoid component of Cuscuta Chinensis Lam., Kaempferol-3-O-glucoside (K-3-G) not only possesses anti-neuroinflammatory potential but also functions as an agonist for ERα and ERβ. This study aimed to determine whether K-3-G improved cognition during the aging process, with an emphasis on its effect on microglial inflammation. In vivo, K-3-G (5 or 10 mg/kg/day) was orally given to the senescence-accelerated mouse prone 8 (SAMP8) mice from six to eight-month old. In addition to mitigating the memory and learning deficits of SAMP8 mice, K-3-G upregulated the expression of ERα and ERβ in their hippocampal CA1 region, with the higher dose being more effective. Less Iba-1+ microglial cells presented in SAMP8 mice treated with K-3-G. The formation of NLR Family Pyrin Domain Containing 3 (NLRP3) complex, production of pro-inflammatory cytokines and oxidative stress-related markers, as well as expression of pro-apoptotic proteins were reduced by K-3-G. In vitro, BV2 microglial cells exposed to oligomeric amyloid beta (Aβ)1-42 were treated with 100 μM K-3-G. K-3-G showed similar anti-inflammatory effects on BV2 cells as in vivo. K-3-G-induced alterations were partly diminished by fulvestrant, an ER antagonist. Moreover, dual-luciferase reporter system demonstrated that K-3-G induced ER expression by activating the transcription of estrogen-response elements (EREs). Collectively, these findings demonstrate that K-3-G may be a novel therapeutic agent for senescence-related cognitive impairment by inhibiting microglial inflammation through its action on ERs.

Sialyltransferase Mutations Alter the Expression of Calcium-Binding Interneurons in Mice Neocortex, Hippocampus and Striatum

Gangliosides are major glycans on vertebrate nerve cells, and their metabolic disruption results in congenital disorders with marked cognitive and motor deficits. The sialyltransferase gene St3gal2 is responsible for terminal sialylation of two prominent brain gangliosides in mammals, GD1a and GT1b. In this study, we analyzed the expression of calcium-binding interneurons in primary sensory (somatic, visual, and auditory) and motor areas of the neocortex, hippocampus, and striatum of St3gal2-null mice as well as St3gal3-null and St3gal2/3-double null. Immunohistochemistry with highly specific primary antibodies for GABA, parvalbumin, calretinin, and calbindin were used for interneuron detection. St3gal2-null mice had decreased expression of all three analyzed types of calcium-binding interneurons in all analyzed regions of the neocortex. These results implicate gangliosides GD1a and GT1b in the process of interneuron migration and maturation.

Neuropathological profile of the African Giant Rat brain (Cricetomys gambianus) after natural exposure to heavy metal environmental pollution in the Nigerian Niger Delta

Pollution by heavy metals is a threat to public health because of the adverse effects on multiple organ systems including the brain. Here, we used the African giant rat (AGR) as a novel sentinel host to assess the effect of heavy metal accumulation and consequential neuropathology upon the brain. For this study, AGR were collected from distinct geographical regions of Nigeria: the rain forest region of south-west Nigeria (Ibadan), the central north of Nigeria (Abuja), and in oil-polluted areas of south Nigeria (Port-Harcourt). We found that zinc, copper, and iron were the major heavy metals that accumulated in the brain and serum of sentinel AGR, with the level of iron highest in animals from Port-Harcourt and least in animals from Abuja. Brain pathology, determined by immunohistochemistry markers of inflammation and oxidative stress, was most severe in animals from Port Harcourt followed by those from Abuja and those from Ibadan were the least affected. The brain pathologies were characterized by elevated brain advanced oxidation protein product (AOPP) levels, neuronal depletion in the prefrontal cortex, severe reactive astrogliosis in the hippocampus and cerebellar white matter, demyelination in the subcortical white matter and cerebellar white matter, and tauopathies. Selective vulnerabilities of different brain regions to heavy metal pollution in the AGR collected from the different regions of the country were evident. In conclusion, we propose that neuropathologies associated with redox dyshomeostasis because of environmental pollution may be localized and contextual, even in a heavily polluted environment. This novel study also highlights African giant rats as suitable epidemiological sentinels for use in ecotoxicological studies.

An enriched maternal environment and stereotypies of sows differentially affect the neuro-epigenome of brain regions related to emotionality in their piglets

Epigenetic mechanisms are important modulators of neurodevelopmental outcomes in the offspring of animals challenged during pregnancy. Pregnant sows living in a confined environment are challenged with stress and lack of stimulation which may result in the expression of stereotypies (repetitive behaviours without an apparent function). Little attention has been devoted to the postnatal effects of maternal stereotypies in the offspring. We investigated how the environment and stereotypies of pregnant sows affected the neuro-epigenome of their piglets. We focused on the amygdala, frontal cortex, and hippocampus, brain regions related to emotionality, learning, memory, and stress response. Differentially methylated regions (DMRs) were investigated in these brain regions of male piglets born from sows kept in an enriched vs a barren environment. Within the latter group of piglets, we compared the brain methylomes of piglets born from sows expressing stereotypies vs sows not expressing stereotypies. DMRs emerged in each comparison. While the epigenome of the hippocampus and frontal cortex of piglets is mainly affected by the maternal environment, the epigenome of the amygdala is mainly affected by maternal stereotypies. The molecular pathways and mechanisms triggered in the brains of piglets by maternal environment or stereotypies are different, which is reflected on the differential gene function associated to the DMRs found in each piglets' brain region . The present study is the first to investigate the neuro-epigenomic effects of maternal enrichment in pigs' offspring and the first to investigate the neuro-epigenomic effects of maternal stereotypies in the offspring of a mammal.

Neural correlates of social exclusion and overinclusion in patients with borderline personality disorder: an fMRI study

BACKGROUND

Interpersonal difficulties of patients with borderline personality disorder (BPD) are closely related to rejection sensitivity. The aim of the present study was to gain further insight into the experience and cerebral processing of social interactions in patients with BPD by using fMRI during experimentally induced experiences of social exclusion, inclusion, and overinclusion.

METHODS

The study involved 30 participants diagnosed with BPD (29 female and 1 male; age: M = 24.22, SD = 5.22) and 30 healthy controls (29 female and 1 male; age: M = 24.66, SD = 5.28) with no current or lifetime psychiatric diagnoses. In the fMRI session, all participants were asked to complete a Cyberball task that consisted of an alternating sequence of inclusion, exclusion, and overinclusion conditions.

RESULTS

Compared to healthy controls, participants with BPD reported higher levels of inner tension and more unpleasant emotions across all experimental conditions. At the neural level, the participants with BPD showed lower recruitment of the left hippocampus in response to social exclusion (relative to the inclusion condition) than the healthy controls did. Lower recruitment of the left hippocampus in this contrast was associated with childhood maltreatment in patients with BPD. However, this difference was no longer significant when we added the covariate of hippocampal volume to the analysis. During social overinclusion (relative to the inclusion condition), we observed no significant differences in a group comparison of neural activation.

CONCLUSIONS

The results of our study suggest that patients with BPD experience more discomfort than do healthy controls during social interactions. Compared to healthy participants, patients with BPD reported more inner tension and unpleasant emotions, irrespective of the extent to which others included them in social interactions. At a neural level, the participants with BPD showed a lower recruitment of the left hippocampus in response to social exclusion than the healthy controls did. The reduced activation of this neural structure could be related to a history of childhood maltreatment and smaller hippocampal volume in patients with BPD.

DMCA-GAN: Dual Multilevel Constrained Attention GAN for MRI-Based Hippocampus Segmentation

Precise segmentation of the hippocampus is essential for various human brain activity and neurological disorder studies. To overcome the small size of the hippocampus and the low contrast of MR images, a dual multilevel constrained attention GAN for MRI-based hippocampus segmentation is proposed in this paper, which is used to provide a relatively effective balance between suppressing noise interference and enhancing feature learning. First, we design the dual-GAN backbone to effectively compensate for the spatial information damage caused by multiple pooling operations in the feature generation stage. Specifically, dual-GAN performs joint adversarial learning on the multiscale feature maps at the end of the generator, which yields an average Dice coefficient (DSC) gain of 5.95% over the baseline. Next, to suppress MRI high-frequency noise interference, a multilayer information constraint unit is introduced before feature decoding, which improves the sensitivity of the decoder to forecast features by 5.39% and effectively alleviates the network overfitting problem. Then, to refine the boundary segmentation effects, we construct a multiscale feature attention restraint mechanism, which forces the network to concentrate more on effective multiscale details, thus improving the robustness. Furthermore, the dual discriminators D1 and D2 also effectively prevent the negative migration phenomenon. The proposed DMCA-GAN obtained a DSC of 90.53% on the Medical Segmentation Decathlon (MSD) dataset with tenfold cross-validation, which is superior to the backbone by 3.78%.

Unraveling Neuronal Identities Using SIMS: A Deep Learning Label Transfer Tool for Single-Cell RNA Sequencing Analysis

Large single-cell RNA datasets have contributed to unprecedented biological insight. Often, these take the form of cell atlases and serve as a reference for automating cell labeling of newly sequenced samples. Yet, classification algorithms have lacked the capacity to accurately annotate cells, particularly in complex datasets. Here we present SIMS (Scalable, Interpretable Machine Learning for Single-Cell), an end-to-end data-efficient machine learning pipeline for discrete classification of single-cell data that can be applied to new datasets with minimal coding. We benchmarked SIMS against common single-cell label transfer tools and demonstrated that it performs as well or better than state of the art algorithms. We then use SIMS to classify cells in one of the most complex tissues: the brain. We show that SIMS classifies cells of the adult cerebral cortex and hippocampus at a remarkably high accuracy. This accuracy is maintained in trans-sample label transfers of the adult human cerebral cortex. We then apply SIMS to classify cells in the developing brain and demonstrate a high level of accuracy at predicting neuronal subtypes, even in periods of fate refinement, shedding light on genetic changes affecting specific cell types across development. Finally, we apply SIMS to single cell datasets of cortical organoids to predict cell identities and unveil genetic variations between cell lines. SIMS identifies cell-line differences and misannotated cell lineages in human cortical organoids derived from different pluripotent stem cell lines. When cell types are obscured by stress signals, label transfer from primary tissue improves the accuracy of cortical organoid annotations, serving as a reliable ground truth. Altogether, we show that SIMS is a versatile and robust tool for cell-type classification from single-cell datasets.

Mapping the macrostructure and microstructure of the in vivo human hippocampus using diffusion MRI

The hippocampus is classically divided into mesoscopic subfields which contain varying microstructure that contribute to their unique functional roles. It has been challenging to characterize this microstructure with current magnetic resonance based neuroimaging techniques. In this work, we used diffusion magnetic resonance imaging (dMRI) and a novel surface-based approach in the hippocampus which revealed distinct microstructural distributions of neurite density and dispersion, T1w/T2w ratio as a proxy for myelin content, fractional anisotropy, and mean diffusivity. We used the neurite orientation dispersion and density imaging (NODDI) model optimized for grey matter diffusivity to characterize neurite density and dispersion. We found that neurite dispersion was highest in the cornu ammonis (CA) 1 and subiculum subfields which likely captures the large heterogeneity of tangential and radial fibres, such as the Schaffer collaterals, perforant path, and pyramidal neurons. Neurite density and T1w/T2w were highest in the subiculum and CA3 and lowest in CA1, which may reflect known myeloarchitectonic differences between these subfields. Using a simple logistic regression model, we showed that neurite density, dispersion, and T1w/T2w measures were separable across the subfields, suggesting that they may be sensitive to the known variability in subfield cyto- and myeloarchitecture. We report macrostructural measures of gyrification, thickness, and curvature that were in line with ex vivo descriptions of hippocampal anatomy. We employed a multivariate orthogonal projective non-negative matrix factorization (OPNNMF) approach to capture co-varying regions of macro- and microstructure across the hippocampus. The clusters were highly variable along the medial-lateral (proximal-distal) direction, likely reflecting known differences in morphology, cytoarchitectonic profiles, and connectivity. Finally, we show that by examining the main direction of diffusion relative to canonical hippocampal axes, we could identify regions with stereotyped microstructural orientations that may map onto specific fibre pathways, such as the Schaffer collaterals, perforant path, fimbria, and alveus. These results highlight the value of combining in vivo dMRI with computational approaches for capturing hippocampal microstructure, which may provide useful features for understanding cognition and for diagnosis of disease states.

Hippocampal atrophy is associated with hearing loss in cognitively normal adults

Objectives

A growing body of evidence suggests that age-related hearing loss (HL) is associated with morphological changes of the cerebral cortex, but the results have been drawn from a small amount of data in most studies. The aim of this study is to investigate the correlation between HL and gray matter volume (GMV) in a large number of subjects, strictly controlling for an extensive set of possible biases.

Methods

Medical records of 576 subjects who underwent pure tone audiometry, brain magnetic resonance imaging (MRI), and the Korean Mini-Mental State Exam (K-MMSE) were reviewed. Among them, subjects with normal cognitive function and free of central nervous system disorders or coronary artery disease were included. Outliers were excluded after a sample homogeneity check. In the end, 405 subjects were enrolled. Pure tone hearing thresholds were determined at 0.5, 1, 2, and 4 kHz in the better ear. Enrolled subjects were divided into 3 groups according to pure tone average: normal hearing (NH), mild HL (MHL), and moderate-to-severe HL (MSHL) groups. Using voxel-based morphometry, we evaluated GMV changes that may be associated with HL. Sex, age, total intracranial volume, type of MRI scanner, education level, K-MMSE score, smoking status, and presence of hypertension, diabetes mellitus and dyslipidemia were used as covariates.

Results

A statistically significant negative correlation between the hearing thresholds and GMV of the hippocampus was elucidated. Additionally, in group comparisons, the left hippocampal GMV of the MSHL group was significantly smaller than that of the NH and MHL groups.

Conclusion

Based on the negative correlation between hearing thresholds and hippocampal GMV in cognitively normal old adults, the current study indicates that peripheral deafferentation could be a potential contributing factor to hippocampal atrophy.

Lateralization of the hippocampus: A review of molecular, functional, and physiological properties in health and disease

The hippocampus is a part of the brain's medial temporal lobe that is located under the cortex. It belongs to the limbic system and helps to collect and transfer information from short-term to long-term memory, as well as spatial orientation in each mammalian brain hemisphere. After more than two centuries of research in brain asymmetry, the hippocampus has attracted much attention in the study of brain lateralization. The hippocampus is very important in cognitive disorders, related to seizures and dementia, such as epilepsy and Alzheimer's disease. In addition, the motivation to study the hippocampus has increased significantly due to the asymmetry in the activity of the left and right hippocampi in healthy people, and its disruption during some neurological diseases. After a general review of the hippocampal structure and its importance in related diseases, the asymmetry in the brain with a focus on the hippocampus during the growth and maturation of healthy people, as well as the differences created in patients at the molecular, functional, and physiological levels are discussed. Most previous work indicates that the hippocampus is lateralized in healthy people. Also, lateralization at different levels remarkably changes in patients, and it appears that the most complex cognitive disorder is caused by a new dominant asymmetric system.

The effects of myricitrin and chebulinic acid on the rat hippocampus exposed to gamma radiation: A stereological, histochemical and biochemical study

AIM

Gamma radiation, a form of ionizing radiation, is used in many different areas, especially in the health field and in the treatment of cancer. However, gamma radiation used for therapeutic purposes also has numerous harmful effects on human health. This study was planned to investigate the impacts of exposure to gamma radiation on the hippocampal area and the preventive effects of myricitrin and chebulinic acid against that damage.

MATERIAL AND METHOD

Thirty-six male Wistar albino rats were randomly divided into six groups. The control group was exposed to no treatment. The chebulinic acid and myricitrin groups were injected with the relevant drug at a dosage of 0.033 mg/kg) (vehicle; normal saline) per day. The gamma groups were placed in a plexiglass test setup with their heads positioned close to the source. The subjects were exposed to radiation with a mixed source containing radioactive Cs-137 and Co-60 isotopes obtained from Ondokuz Mayıs University Physics Department Nuclear Physics Laboratory for 1 h. Gamma radiation was applied 16 mGy for one hour per day for 10 days. The gamma radiation+chebulinic acid and the gamma radiation myricitrin groups also received 0.033 mg/kg per day of these drugs via injection. Immediately after the experimental procedure, all animals were subjected to behavioural tests, and perfused brain tissues were analyzed using stereological methods.

RESULTS

Stereological analysis showed that gamma radiation caused a decrease in the numbers of neurons in the hippocampal area (p < 0.01; One-way ANOVA) and that chebulinic acid and myricitrin reduced this decrease (p < 0.01; One-way ANOVA). Decreases in learning and memory capacity were detected in behavioural tests in rats from the Gamma group.

CONCLUSION

The study findings showed that that the adverse health effects of Gamma radiation can be ameliorated using myricitrin and chebulinic acid. Myricitrin was more effective in terms of cell proliferation and defence against oxidative stress than chebulinic acid, and exhibited a more neuroprotective effect. However, more detailed analyses should be performed before using either antioxidant for therapeutic purposes.

Gender and cytoarchitecture differences: Functional connectivity of the hippocampal sub-regions

Introduction

The hippocampus plays a significant role in learning, memory encoding, and spatial navigation. Typically, the hippocampus is investigated as a whole region of interest. However, recent work has developed fully detailed atlases based on cytoarchitecture properties of brain regions, and the hippocampus has been sub-divided into seven sub-areas that have structural differences in terms of distinct numbers of cells, neurons, and other structural and chemical properties. Moreover, gender differences are of increasing concern in neuroscience research. Several neuroscience studies have found structural and functional variations between the brain regions of females and males, and the hippocampus is one of these regions.

Aim

The aim of this study to explore whether the cytoarchitecturally distinct sub-regions of the hippocampus have varying patterns of functional connectivity with different networks of the brain and how these functional connections differ in terms of gender differences.

Method

This study investigated 200 healthy participants using seed-based resting-state functional magnetic resonance imaging (rsfMRI). The primary aim of this study was to explore the resting connectivity and gender distinctions associated with specific sub-regions of the hippocampus and their relationship with major functional brain networks.

Results

The findings revealed that the majority of the seven hippocampal sub-regions displayed functional connections with key brain networks, and distinct patterns of functional connectivity were observed between the hippocampal sub-regions and various functional networks within the brain. Notably, the default and visual networks exhibited the most consistent functional connections. Additionally, gender-based analysis highlighted evident functional resemblances and disparities, particularly concerning the anterior section of the hippocampus.

Conclusion

This study highlighted the functional connectivity patterns and involvement of the hippocampal sub-regions in major brain functional networks, indicating that the hippocampus should be investigated as a region of multiple distinct functions and should always be examined as sub-regions of interest. The results also revealed clear gender differences in functional connectivity.

Mapping the spatial transcriptomic signature of the hippocampus during memory consolidation

Memory consolidation involves discrete patterns of transcriptional events in the hippocampus. Despite the emergence of single-cell transcriptomic profiling techniques, mapping the transcriptomic signature across subregions of the hippocampus has remained challenging. Here, we utilized unbiased spatial sequencing to delineate transcriptome-wide gene expression changes across subregions of the dorsal hippocampus of male mice following learning. We find that each subregion of the hippocampus exhibits distinct yet overlapping transcriptomic signatures. The CA1 region exhibited increased expression of genes related to transcriptional regulation, while the DG showed upregulation of genes associated with protein folding. Importantly, our approach enabled us to define the transcriptomic signature of learning within two less-defined hippocampal subregions, CA1 stratum radiatum, and oriens. We demonstrated that CA1 subregion-specific expression of a transcription factor subfamily has a critical functional role in the consolidation of long-term memory. This work demonstrates the power of spatial molecular approaches to reveal simultaneous transcriptional events across the hippocampus during memory consolidation.

Hippocampus segmentation after brain tumor resection via postoperative region synthesis

PURPOSE

Accurately segmenting the hippocampus is an essential step in brain tumor radiotherapy planning. Some patients undergo brain tumor resection beforehand, which can significantly alter the postoperative regions' appearances and intensity of the 3D MR images. However, there are limited tumor resection patient images for deep neural networks to be effective.

METHODS

We propose a novel automatic hippocampus segmentation framework via postoperative image synthesis. The variational generative adversarial network consists of intensity alignment and a weight-map-guided feature fusion module, which transfers the postoperative regions to the preoperative images. In addition, to further boost the performance of hippocampus segmentation, We design a joint training strategy to optimize the image synthesis network and the segmentation task simultaneously.

RESULTS

Comprehensive experiments demonstrate that our proposed method on the dataset with 48 nasopharyngeal carcinoma patients and 67 brain tumor patients observes consistent improvements over state-of-the-art methods.

CONCLUSION

The proposed postoperative image synthesis method act as a novel and powerful scheme to generate additional training data. Compared with existing deep learning methods, it achieves better accuracy for hippocampus segmentation of brain tumor patients who have undergone brain tumor resection. It can be used as an automatic contouring tool for hippocampus delineation in hippocampus-sparing radiotherapy.

The role of microRNAs in neurobiology and pathophysiology of the hippocampus

MicroRNAs (miRNAs) are short non-coding and well-conserved RNAs that are linked to many aspects of development and disorders. MicroRNAs control the expression of genes related to different biological processes and play a prominent role in the harmonious expression of many genes. During neural development of the central nervous system, miRNAs are regulated in time and space. In the mature brain, the dynamic expression of miRNAs continues, highlighting their functional importance in neurons. The hippocampus, as one of the crucial brain structures, is a key component of major functional connections in brain. Gene expression abnormalities in the hippocampus lead to disturbance in neurogenesis, neural maturation and synaptic formation. These disturbances are at the root of several neurological disorders and behavioral deficits, including Alzheimer's disease, epilepsy and schizophrenia. There is strong evidence that abnormalities in miRNAs are contributed in neurodegenerative mechanisms in the hippocampus through imbalanced activity of ion channels, neuronal excitability, synaptic plasticity and neuronal apoptosis. Some miRNAs affect oxidative stress, inflammation, neural differentiation, migration and neurogenesis in the hippocampus. Furthermore, major signaling cascades in neurodegeneration, such as NF-Kβ signaling, PI3/Akt signaling and Notch pathway, are closely modulated by miRNAs. These observations, suggest that microRNAs are significant regulators in the complicated network of gene regulation in the hippocampus. In the current review, we focus on the miRNA functional role in the progression of normal development and neurogenesis of the hippocampus. We also consider how miRNAs in the hippocampus are crucial for gene expression mechanisms in pathophysiological pathways.

Emergence Patterns from General Anesthesia after Epilepsy Surgery: An Observational Pilot Study

Objective Emergence from anesthesia starts from the limbic structures and then spreads outwards to brainstem, reticular activating systems, and then to the cortex. Epilepsy surgery often involves resection of limbic structures and hence may disrupt the pattern of emergence. The aim of this study was to explore the pattern of emergence from anesthesia following epilepsy surgery and to determine associated variables affecting the emergence pattern. Setting and Design  Tertiary care center, prospective observational study. Materials   and Methods We conducted a prospective observation pilot study on adult patients undergoing anterior temporal lobectomy and amygdalohippocampectomy for epilepsy. Anesthesia management was standardized in all patients, and they were allowed to wake up with "no touch" technique. Primary outcome of the study was the pattern of emergence (normal emergence, agitated emergence, or slow emergence) from anesthesia. Secondary outcomes were to explore the differences in preoperative neuropsychological profile and limbic structure volumes between the different patterns of emergence. Quantitative variables were analyzed using Student's t -test. Qualitative variables were analyzed using chi-square test. Results  Twenty-nine patients completed the study: 9 patients (31%) had agitated emergence, and 20 patients had normal emergence. Among the agitated emergence, 2 patients had Riker scale of 7 indicating violent emergence. Patient demographics, anesthetic used, neuropsychological profile, and limbic structure volumes were similar between normal emergence and agitated emergence groups. However, two patients who had severe agitation (Riker scale of 7) had the lowest intelligence quotient. Conclusion  Our pilot study showed that emergence agitation is not uncommon in patients undergoing epilepsy surgery. However, due to smaller sample size, the role of preoperative neuropsychologic profile and hippocampal volumes in predicting the pattern of emergence is inconclusive.

Dopamine and Glutamate Crosstalk Worsen the Seizure Outcome in TLE-HS Patients

Temporal lobe epilepsy (TLE), accompanied by hippocampal sclerosis (HS), is the most common form of drug-resistant epilepsy (DRE). Nearly 20% of the patients showed seizure recurrence even after surgery, and the reasons are yet to be understood. Dysregulation of neurotransmitters is evident during seizures, which can induce excitotoxicity. The present study focused on understanding the molecular changes associated with Dopamine (DA) and glutamate signaling and their possible impact on the persistence of excitotoxicity and seizure recurrence in patients with drug-resistant TLE-HS who underwent surgery. According to the International League against Epilepsy (ILAE) suggested classification for seizure outcomes, the patients (n = 26) were classified as class 1 (no seizures) and class 2 (persistent seizures) using the latest post-surgery follow-up data to understand the prevalent molecular changes in seizure-free and seizure-recurrence patient groups. Our study uses thioflavin T assay, western blot analysis, immunofluorescence assays, and fluorescence resonance energy transfer (FRET) assays. We have observed a substantial increase in the DA and glutamate receptors that promote excitotoxicity. Patients who had seizure recurrence showed a significant increase in (pNR2B, p < 0.009; and pGluR1, p < 0.01), protein phosphatase1γ (PP1γ; p < 0.009), protein kinase A (PKAc; p < 0.001) and dopamine-cAMP regulated phospho protein32 (pDARPP32T34; p < 0.009) which are critical for long-term potentiation (LTP), excitotoxicity compared to seizure-free patients and controls. A significant increase in D1R downstream kinases like PKA (p < 0.001), pCAMKII (p < 0.009), and Fyn (p < 0.001) was observed in patient samples compared to controls. Anti-epileptic DA receptor D2R was found to be decreased in ILAE class 2 (p < 0.02) compared to class 1. Since upregulation of DA and glutamate signaling supports LTP and excitotoxicity, we believe it could impact seizure recurrence. Further studies about the impact of DA and glutamate signaling on the distribution of PP1γ at postsynaptic density and synaptic strength could help us understand the seizure microenvironment in patients. Dopamine, Glutamate signal crosstalk. Diagram representing the PP1γ regulation by NMDAR negative feedback inhibition signaling (green circle-left) and D1R signal (red circle-middle) domination over PP1γ though increased PKA, pDARPP32T34, and supports pGluR1, pNR2B in seizure recurrent patients. D1R-D2R hetero dimer activation (red circle-right) increases cellular Ca2+ and pCAMKIIα activation. All these events lead to calcium overload in HS patients and excitotoxicity, particularly in patients experiencing recurrent seizures.

Spaceflight-Induced Gene Expression Profiles in the Mouse Brain Are Attenuated by Treatment with the Antioxidant BuOE

The demands of deep space pose a health risk to the central nervous system that has long been a concern when sending humans to space. While little is known about how spaceflight affects transcription spatially in the brain, a greater understanding of this process has the potential to aid strategies that mitigate the effects of spaceflight on the brain. Therefore, we performed GeoMx Digital Spatial Profiling of mouse brains subjected to either spaceflight or grounded controls. Four brain regions were selected: Cortex, Frontal Cortex, Corunu Ammonis I, and Dentate Gyrus. Antioxidants have emerged as a potential means of attenuating the effects of spaceflight, so we treated a subset of the mice with a superoxide dismutase mimic, MnTnBuOE-2-PyP 5+ (BuOE). Our analysis revealed hundreds of differentially expressed genes due to spaceflight in each of the four brain regions. Both common and region-specific transcriptomic responses were observed. Metabolic pathways and pathways sensitive to oxidative stress were enriched in the four brain regions due to spaceflight. These findings enhance our understanding of brain regional variation in susceptibility to spaceflight conditions. BuOE reduced the transcriptomic effects of spaceflight at a large number of genes, suggesting that this compound may attenuate oxidative stress-induced brain damage caused by the spaceflight environment.

Sex Differences in the Neurobiology of Stress

This review highlights the existing knowledge and data that explain the physiologic impacts of stress, especially pertaining to neurobiology, and how these impacts differ by sex. Furthermore, this review explains the benefits of interventions aimed at preventing or mitigating the adverse effects of stress, because of both the significant toll of stress on the body and the disproportionate impact of these changes experienced by women.

Hierarchical based classification method based on fusion of Gaussian map descriptors for Alzheimer diagnosis using T1-weighted magnetic resonance imaging

Alzheimer's disease (AD) is considered one of the most spouting elderly diseases. In 2015, AD is reported the US's sixth cause of death. Substantially, non-invasive imaging is widely employed to provide biomarkers supporting AD screening, diagnosis, and progression. In this study, Gaussian descriptors-based features are proposed to be efficient new biomarkers using Magnetic Resonance Imaging (MRI) T1-weighted images to differentiate between Alzheimer's disease (AD), Mild Cognitive Impairment (MCI), and Normal controls (NC). Several Gaussian map-based features are extracted such as Gaussian shape operator, Gaussian curvature, and mean curvature. The aforementioned features are then introduced to the Support Vector Machine (SVM). They were, first, calculated separately for the Hippocampus and Amygdala. Followed by the fusion of the features. Moreover, Fusion of the regions before feature extraction was also employed. Alzheimer's disease Neuroimaging Initiative (ADNI) dataset, formed of 45, 55, and 65 cases for AD, MCI, and NC respectively, is appointed in this study. The shape operator feature outperformed the other features, with 74.6%, and 98.9% accuracy in the case of normal vs. abnormal, and AD vs. MCI classification respectively.

Bioreducible Gene Delivery Platform that Promotes Intracellular Payload Release and Widespread Brain Dispersion

We here introduce a novel bioreducible polymer-based gene delivery platform enabling widespread transgene expression in multiple brain regions with therapeutic relevance following intracranial convection-enhanced delivery. Our bioreducible nanoparticles provide markedly enhanced gene delivery efficacy in vitro and in vivo compared to nonbiodegradable nanoparticles primarily due to the ability to release gene payloads preferentially inside cells. Remarkably, our platform exhibits competitive gene delivery efficacy in a neuron-rich brain region compared to a viral vector under previous and current clinical investigations with demonstrated positive outcomes. Thus, our platform may serve as an attractive alternative for the intracranial gene therapy of neurological disorders.

Energy metabolism and behavioral parameters in female mice subjected to obesity and offspring deprivation stress

This study aimed to evaluate the behavioral and energy metabolism parameters in female mice subjected to obesity and offspring deprivation (OD) stress. Eighty female Swiss mice, 40 days old, were weighed and divided into two groups: Control group (control diet, n = 40) and Obese group (high-fat diet, n = 40), for induction of the animal model of obesity, the protocol was based on the consumption of a high-fat diet and lasted 8 weeks. Subsequently, the females were subjected to pregnancy, after the birth of the offspring, were divided again into the following groups (n = 20): Control non-deprived (ND), Control + OD, Obese ND, and Obese + OD, for induction of the stress protocol by OD. After the offspring were 21 days old, weaning was performed and the dams were subjected to behavioral tests. The animals were humanely sacrificed, the brain was removed, and brain structures were isolated to assess energy metabolism. Both obesity and OD led to anhedonia in the dams. It was shown that the structures most affected by obesity and OD are the hypothalamus and hippocampus, as evidenced by the mitochondrial dysfunction found in these structures. When analyzing the groups separately, it was observed that OD led to more pronounced mitochondrial damage; however, the association of obesity with OD, as well as obesity alone, also generated damage. Thus, it is concluded that obesity and OD lead to anhedonia in animals and to mitochondrial dysfunction in the hypothalamus and hippocampus, which may lead to losses in feeding control and cognition of the dams.

Polystyrene Microplastics Exacerbate Systemic Inflammation in High-Fat Diet-Induced Obesity

Microplastics (MPs) are recognized as environmental pollutants with potential implications for human health. Considering the rapid increase in obesity rates despite stable caloric intake, there is a growing concern about the link between obesity and exposure to environmental pollutants, including MPs. In this study, we conducted a comprehensive investigation utilizing in silico, in vitro, and in vivo approaches to explore the brain distribution and physiological effects of MPs. Molecular docking simulations were performed to assess the binding affinity of three plastic polymers (ethylene, propylene, and styrene) to immune cells (macrophages, CD4+, and CD8+ lymphocytes). The results revealed that styrene exhibited the highest binding affinity for macrophages. Furthermore, in vitro experiments employing fluorescence-labeled PS-MPs (fPS-MPs) of 1 μm at various concentrations demonstrated a dose-dependent binding of fPS-MPs to BV2 murine microglial cells. Subsequent oral administration of fPS-MPs to high-fat diet-induced obese mice led to the co-existence of fPS-MPs with immune cells in the blood, exacerbating impaired glucose metabolism and insulin resistance and promoting systemic inflammation. Additionally, fPS-MPs were detected throughout the brain, with increased activation of microglia in the hypothalamus. These findings suggest that PS-MPs significantly contribute to the exacerbation of systemic inflammation in high-fat diet-induced obesity by activating peripheral and central inflammatory immune cells.

Volumes of hippocampal subfields suggest a continuum between schizophrenia, major depressive disorder and bipolar disorder

Objective

There is considerable debate as to whether the continuum of major psychiatric disorders exists and to what extent the boundaries extend. Converging evidence suggests that alterations in hippocampal volume are a common sign in psychiatric disorders; however, there is still no consensus on the nature and extent of hippocampal atrophy in schizophrenia (SZ), major depressive disorder (MDD) and bipolar disorder (BD). The aim of this study was to verify the continuum of SZ - BD - MDD at the level of hippocampal subfield volume and to compare the volume differences in hippocampal subfields in the continuum.

Methods

A total of 412 participants (204 SZ, 98 MDD, and 110 BD) underwent 3 T MRI scans, structured clinical interviews, and clinical scales. We segmented the hippocampal subfields with FreeSurfer 7.1.1 and compared subfields volumes across the three diagnostic groups by controlling for age, gender, education, and intracranial volumes.

Results

The results showed a gradual increase in hippocampal subfield volumes from SZ to MDD to BD. Significant volume differences in the total hippocampus and 13 of 26 hippocampal subfields, including CA1, CA3, CA4, GC-ML-DG, molecular layer and the whole hippocampus, bilaterally, and parasubiculum in the right hemisphere, were observed among diagnostic groups. Medication treatment had the most effect on subfields of MDD compared to SZ and BD. Subfield volumes were negatively correlated with illness duration of MDD. Positive correlations were found between subfield volumes and drug dose in SZ and MDD. There was no significant difference in laterality between diagnostic groups.

Conclusion

The pattern of hippocampal volume reduction in SZ, MDD and BD suggests that there may be a continuum of the three disorders at the hippocampal level. The hippocampus represents a phenotype that is distinct from traditional diagnostic strategies. Combined with illness duration and drug intervention, it may better reflect shared pathophysiology and mechanisms across psychiatric disorders.

Imaging crossing fibers in mouse, pig, monkey, and human brain using small-angle X-ray scattering

Myelinated axons (nerve fibers) efficiently transmit signals throughout the brain via action potentials. Multiple methods that are sensitive to axon orientations, from microscopy to magnetic resonance imaging, aim to reconstruct the brain's structural connectome. As billions of nerve fibers traverse the brain with various possible geometries at each point, resolving fiber crossings is necessary to generate accurate structural connectivity maps. However, doing so with specificity is a challenging task because signals originating from oriented fibers can be influenced by brain (micro)structures unrelated to myelinated axons. X-ray scattering can specifically probe myelinated axons due to the periodicity of the myelin sheath, which yields distinct peaks in the scattering pattern. Here, we show that small-angle X-ray scattering (SAXS) can be used to detect myelinated, axon-specific fiber crossings. We first demonstrate the capability using strips of human corpus callosum to create artificial double- and triple-crossing fiber geometries, and we then apply the method in mouse, pig, vervet monkey, and human brains. We compare results to polarized light imaging (3D-PLI), tracer experiments, and to outputs from diffusion MRI that sometimes fails to detect crossings. Given its specificity, capability of 3-dimensional sampling and high resolution, SAXS could serve as a ground truth for validating fiber orientations derived using diffusion MRI as well as microscopy-based methods. STATEMENT OF SIGNIFICANCE: To study how the nerve fibers in our brain are interconnected, scientists need to visualize their trajectories, which often cross one another. Here, we show the unique capacity of small-angle X-ray scattering (SAXS) to study these fiber crossings without use of labeling, taking advantage of SAXS's specificity to myelin - the insulating sheath that is wrapped around nerve fibers. We use SAXS to detect double and triple crossing fibers and unveil intricate crossings in mouse, pig, vervet monkey, and human brains. This non-destructive method can uncover complex fiber trajectories and validate other less specific imaging methods (e.g., MRI or microscopy), towards accurate mapping of neuronal connectivity in the animal and human brain.

Hippocampal Volume in Children with Attention Deficit Hyperactivity Disorder and Speech and Language Delay

Introduction

Hippocampus is a complex brain structure located deep in the temporal lobes of the brain. The structure has been implicated in several disorders related to cognition. Reports are emerging of its involvement in attention deficit hyperactivity disorder (ADHD). The current study was planned to assess the volume of the hippocampus in children with ADHD and speech and language delay with normal birth history using magnetic resonance imaging (MRI) of the brain.

Material and Methods

MRI brain of 12 children (age range = 3-6 years) and 22 controls with clinical diagnosis of ADHD as per Diagnostic and Statistical Manual-5 were obtained in oblique coronal sequence (T1 weighted). The entire hippocampus formation was outlined manually using Image-J software available freely from www.freesurfer.com. Results were expressed as volume cubic millimeters ± SD.

Results

Volumes of the hippocampi of children with ADHD were 2450.2 ± 667 mm3 (R) and 2505.8 ± 878.5 mm3 (L), respectively. The mean volume (bilateral) of the cases was 2478 ± 772.75 mm3. The right hippocampal volume of the controls was 3255.8 ± 1374.3 mm3 (R) and that of the left side was 3159.3 ± 1451 (L) mm3, respectively.

Conclusion

Current study reported a substantial shrinkage (23%) of the left and right hippocampus in children with ADHD compared to controls.

PRO: Do We Still Need Whole-Brain Irradiation for Brain Metastases?

(1) Background: In recent decades, the use of whole-brain radiation therapy (WBRT) in the treatment of brain metastases has significantly decreased, with clinicians fearing adverse neurocognitive events and data showing limited efficacy regarding local tumor control and overall survival. The present study thus aimed to reassess the role that WBRT holds in the treatment of brain metastases. (2) Methods: This review summarizes the available evidence from 1990 until today supporting the use of WBRT, as well as new developments in WBRT and their clinical implications. (3) Results: While one to four brain metastases should be exclusively treated with radiosurgery, WBRT does remain an option for patients with multiple metastases. In particular, hippocampus-avoidance WBRT, WBRT with dose escalation to the metastases, and their combination have shown promising results and offer valid alternatives to local stereotactic radiotherapy. Ongoing and published prospective trials on the efficacy and toxicity of these new methods are presented. (4) Conclusions: Unlike conventional WBRT, which has limited indications, modern WBRT techniques continue to have a significant role to play in the treatment of multiple brain metastases. In which situations radiosurgery or WBRT should be the first option should be investigated in further studies. Until then, the therapeutic decision must be made individually depending on the oncological context.