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The polyphenol resveratrol has been suggested to exert beneficial effects on memory and the aging hippocampus due to calorie-restriction mimicking effects. However, the evidence based on human interventional studies is scarce. We therefore aimed to determine the effects of resveratrol on memory performance, and to identify potential underlying mechanisms using a broad array of blood-based biomarkers as well as hippocampus connectivity and microstructure assessed with ultra-high field magnetic resonance imaging (UHF-MRI). In this double-blind, randomized controlled trial, 60 elderly participants (60–79 years) with a wide body-mass index (BMI) range of 21–37 kg/m2 were randomized to receive either resveratrol (200 mg/day) or placebo for 26 weeks (registered at ClinicalTrials.gov: NCT02621554). Baseline and follow-up assessments included the California Verbal Learning Task (CVLT, main outcome), the ModBent task, anthropometry, markers of glucose and lipid metabolism, inflammation and neurotrophins derived from fasting blood, multimodal neuroimaging at 3 and 7 T, and questionnaires to assess confounding factors. Multivariate repeated-measures ANOVA did not detect significant time by group effects for CVLT performance. There was a trend for preserved pattern recognition memory after resveratrol, while performance decreased in the placebo group (n.s., p = 0.07). Further exploratory analyses showed increases in both groups over time in body fat, cholesterol, fasting glucose, interleukin 6, high sensitive C-reactive protein, tumor necrosis factor alpha and in mean diffusivity of the subiculum and presubiculum, as well as decreases in physical activity, brain-derived neurotrophic factor and insulin-like growth factor 1 at follow-up, which were partly more pronounced after resveratrol. This interventional study failed to show significant improvements in verbal memory after 6 months of resveratrol in healthy elderly with a wide BMI range. A non-significant trend emerged for positive effects on pattern recognition memory, while possible confounding effects of unfavorable changes in lifestyle behavior, neurotrophins and inflammatory markers occurred. Our findings also indicate the feasibility to detect (un)healthy aging-related changes in measures of hippocampus microstructure after 6 months using 7T diffusion MRI. More studies incorporating a longer duration and larger sample size are needed to determine if resveratrol enhances memory performance in healthy older adults. •In this randomized clinical trial, 6 months resveratrol supplementation showed no significant effects on verbal memory compared to placebo.•Unfavorable changes in lifestyle factors at follow-up might have introduced confounding.•Secondary analyses showed a trend towards preserved pattern recognition.•We used multimodal ultra high field MRI to detect subtle changes in microstructure of hippocampus subfields.

Background Cognitive impairment is a prominent feature that adversely affects the long-term prognosis of schizophrenia; yet effective clinical strategies for treatment remain limited. Disruptions in the tricarboxylic acid (TCA) cycle and functional brain abnormalities in the hippocampus may underlie cognitive deficits, although the intrinsic connections between these factors have yet to be fully elucidated. Notably, metformin, a biguanide anti-hyperglycemic agent, has been shown to improve several cognitive domains in patients with schizophrenia and may have the potential to regulate the TCA cycle. Previously, we found the cognitive improvement effect of adding metformin. In this study, we will further explore the relationship between cognitive improvement and TCA cycle metabolites and brain function. Methods This study included 58 patients with schizophrenia who were in similar clinical conditions and assigned to 24-week 1500 mg metformin add-on treatment or the control group. We used the liquid chromatography tandem mass spectrometry (LC–MS/MS) method to detect the levels of key TCA cycle metabolites in the blood of schizophrenia patients, conducted MRI scans, and assessed clinical condition using the Positive and Negative Syndrome Scale (PANSS) and cognitive performance using the Chinese version of MATRICS Consensus Cognitive Battery (MCCB). Results Twenty-four weeks of metformin treatment downregulated levels of upstream lactic acid (− 80.81 (− 96.85, − 64.77) μg/mL at week 24) and pyruvic acid (− 17.51 (− 20.52, − 14.49) μg/mL at week 24), while upregulating levels of other seven downstream metabolites in TCA cycle (all p values < 0.001). Functional connectivity between left caudal hippocampus and right medio ventral occipital cortex (week 12, between-group difference =  − 0.334), and right caudal hippocampus and right middle frontal gyrus (week 24, between-group difference = 0.284) were significantly different between groups ( p  < 0.001). Moreover, metformin-improved cognition (working memory and verbal learning) and hippocampal functional connectivity (right caudal hippocampus and right middle frontal gyrus) were associated with changes in TCA cycle metabolites. Limitation Limited sample size and follow-up time, and lack of in-depth mechanism exploration. Conclusions Our results suggested that repurposing of metformin may have the potential to improve cognition by regulating energy metabolism pathways. Clinical trials registration NCT03271866. Graphical Abstract

Recruitment of young neurons to the hippocampus decreases rapidly during the first years of life, and neurogenesis does not continue, or is extremely rare, in the adult human brain. No new neurons in adult humans Previous lines of evidence have suggested that neural precursors are present in adult humans and continue to generate new neurons in the hippocampus even after full maturation. Here, Arturo Alvarez-Buylla and colleagues re-visit that concept and come to a different conclusion. Using a more comprehensive and larger set of samples of human hippocampus than those analysed in previous studies, the authors find evidence for the production of new neurons early in life, but note that hippocampal neurogenesis rates decline rapidly within the first few years of childhood. The authors were unable to detect the production of any new neurons in adults. The same patterns of neurogenesis were observed in rhesus macaques. New neurons continue to be generated in the subgranular zone of the dentate gyrus of the adult mammalian hippocampus 1 , 2 , 3 , 4 , 5 . This process has been linked to learning and memory, stress and exercise, and is thought to be altered in neurological disease 6 , 7 , 8 , 9 , 10 . In humans, some studies have suggested that hundreds of new neurons are added to the adult dentate gyrus every day 11 , whereas other studies find many fewer putative new neurons 12 , 13 , 14 . Despite these discrepancies, it is generally believed that the adult human hippocampus continues to generate new neurons. Here we show that a defined population of progenitor cells does not coalesce in the subgranular zone during human fetal or postnatal development. We also find that the number of proliferating progenitors and young neurons in the dentate gyrus declines sharply during the first year of life and only a few isolated young neurons are observed by 7 and 13 years of age. In adult patients with epilepsy and healthy adults (18–77 years; n  = 17 post-mortem samples from controls; n  = 12 surgical resection samples from patients with epilepsy), young neurons were not detected in the dentate gyrus. In the monkey ( Macaca mulatta ) hippocampus, proliferation of neurons in the subgranular zone was found in early postnatal life, but this diminished during juvenile development as neurogenesis decreased. We conclude that recruitment of young neurons to the primate hippocampus decreases rapidly during the first years of life, and that neurogenesis in the dentate gyrus does not continue, or is extremely rare, in adult humans. The early decline in hippocampal neurogenesis raises questions about how the function of the dentate gyrus differs between humans and other species in which adult hippocampal neurogenesis is preserved.

Elevated hippocampal perfusion has been observed in people at clinical high risk for psychosis (CHR-P). Preclinical evidence suggests that hippocampal hyperactivity is central to the pathophysiology of psychosis, and that peripubertal treatment with diazepam can prevent the development of psychosis-relevant phenotypes. The present experimental medicine study examined whether diazepam can normalize hippocampal perfusion in CHR-P individuals. Using a randomized, double-blind, placebo-controlled, crossover design, 24 CHR-P individuals were assessed with magnetic resonance imaging (MRI) on two occasions, once following a single oral dose of diazepam (5 mg) and once following placebo. Regional cerebral blood flow (rCBF) was measured using 3D pseudo-continuous arterial spin labeling and sampled in native space using participant-specific hippocampus and subfield masks (CA1, subiculum, CA4/dentate gyrus). Twenty-two healthy controls (HC) were scanned using the same MRI acquisition sequence, but without administration of diazepam or placebo. Mixed-design ANCOVAs and linear mixed-effects models were used to examine the effects of group (CHR-P placebo/diazepam vs. HC) and condition (CHR-P diazepam vs. placebo) on rCBF in the hippocampus as a whole and by subfield. Under the placebo condition, CHR-P individuals (mean [±SD] age: 24.1 [±4.8] years, 15 F) showed significantly elevated rCBF compared to HC (mean [±SD] age: 26.5 [±5.1] years, 11 F) in the hippocampus ( F (1,41) = 24.7, p FDR  < 0.001) and across its subfields (all p FDR  < 0.001). Following diazepam, rCBF in the hippocampus (and subfields, all p FDR  < 0.001) was significantly reduced ( t (69) = −5.1, p FDR  < 0.001) and normalized to HC levels ( F (1,41) = 0.4, p FDR  = 0.204). In conclusion, diazepam normalized hippocampal hyperperfusion in CHR-P individuals, consistent with evidence implicating medial temporal GABAergic dysfunction in increased vulnerability for psychosis.

A single dose of psilocybin, a psychedelic that acutely causes distortions of space–time perception and ego dissolution, produces rapid and persistent therapeutic effects in human clinical trials 1 – 4 . In animal models, psilocybin induces neuroplasticity in cortex and hippocampus 5 – 8 . It remains unclear how human brain network changes relate to subjective and lasting effects of psychedelics. Here we tracked individual-specific brain changes with longitudinal precision functional mapping (roughly 18 magnetic resonance imaging visits per participant). Healthy adults were tracked before, during and for 3 weeks after high-dose psilocybin (25 mg) and methylphenidate (40 mg), and brought back for an additional psilocybin dose 6–12 months later. Psilocybin massively disrupted functional connectivity (FC) in cortex and subcortex, acutely causing more than threefold greater change than methylphenidate. These FC changes were driven by brain desynchronization across spatial scales (areal, global), which dissolved network distinctions by reducing correlations within and anticorrelations between networks. Psilocybin-driven FC changes were strongest in the default mode network, which is connected to the anterior hippocampus and is thought to create our sense of space, time and self. Individual differences in FC changes were strongly linked to the subjective psychedelic experience. Performing a perceptual task reduced psilocybin-driven FC changes. Psilocybin caused persistent decrease in FC between the anterior hippocampus and default mode network, lasting for weeks. Persistent reduction of hippocampal-default mode network connectivity may represent a neuroanatomical and mechanistic correlate of the proplasticity and therapeutic effects of psychedelics. Healthy adults were tracked before, during and after high doses of psilocybin and methylphenidate to assess how psychedelics can change human brain networks, and psilocybin was found to massively disrupt functional connectivity in cortex and subcortex with some changes persisting for weeks.

Studies of patients with major depressive disorder (MDD) have consistently reported reduced hippocampal volumes; however, the exact pattern of these volume changes in specific anatomical subfields and their functional significance is unclear. We sought to clarify the relationship between hippocampal tail volumes and (i) a diagnosis of MDD, and (ii) clinical remission to anti-depressant medications (ADMs). Outpatients with nonpsychotic MDD (n=202) based on DSM-IV criteria and a 17-item Hamilton Rating Scale for Depression (HRSD17) score ⩾16 underwent pretreatment magnetic resonance imaging as part of the international Study to Predict Optimized Treatment for Depression (iSPOT-D). Gender-matched healthy controls (n=68) also underwent MRI scanning. An automated pipeline was used to objectively measure hippocampal subfield and whole brain volumes. Remission was defined as an HRSD17 of ⩽7 following 8 weeks of randomized open-label treatment ADMs: escitalopram, sertraline or venlafaxine-extended release. After controlling for age and total brain volume, hippocampal tail volume was larger in the MDD cohort compared to control subjects. Larger hippocampal tail volume was positively related to clinical remission, independent of total hippocampal volume, total brain volume and age. These data provide convergent evidence of the importance of the hippocampus in the development or treatment of MDD. Hippocampal tail volume is proposed as a potentially useful biomarker of sensitivity to ADM treatment.

Metabolic production of acetyl coenzyme A (acetyl-CoA) is linked to histone acetylation and gene regulation, but the precise mechanisms of this process are largely unknown. Here we show that the metabolic enzyme acetyl-CoA synthetase 2 (ACSS2) directly regulates histone acetylation in neurons and spatial memory in mammals. In a neuronal cell culture model, ACSS2 increases in the nuclei of differentiating neurons and localizes to upregulated neuronal genes near sites of elevated histone acetylation. A decrease in ACSS2 lowers nuclear acetyl-CoA levels, histone acetylation, and responsive expression of the cohort of neuronal genes. In adult mice, attenuation of hippocampal ACSS2 expression impairs long-term spatial memory, a cognitive process that relies on histone acetylation. A decrease in ACSS2 in the hippocampus also leads to defective upregulation of memory-related neuronal genes that are pre-bound by ACSS2. These results reveal a connection between cellular metabolism, gene regulation, and neural plasticity and establish a link between acetyl-CoA generation ‘on-site’ at chromatin for histone acetylation and the transcription of key neuronal genes. The metabolic enzyme acetyl coenzyme A synthetase directly regulates gene expression during memory formation by binding to specific genes and providing acetyl coenzyme A for histone acetylation. Nuclear acetyl-CoA in memory formation The regulation of neuronal gene transcription during memory formation involves histone acetylation, which is critical to long-term memory consolidation. Here, Shelley Berger and colleagues show that in neurons the metabolic enzyme acetyl coenzyme A synthetase 2 (ACSS2) associates with chromatin to increase local concentrations of acetyl coenzyme A and to promote histone acetylation and transcription of neural genes. In the mouse hippocampus, ACSS2 expression is required for the expression of neuronal genes involved in memory and the acquisition of long-term memories. These results reveal a direct role of a metabolic enzyme in acetylating histones and connect acetate metabolism to neuronal gene regulation and neural plasticity.

The hippocampus is essential for spatial and episodic memory but is damaged early in Alzheimer’s disease and is very sensitive to hypoxia. Understanding how it regulates its oxygen supply is therefore key for designing interventions to preserve its function. However, studies of neurovascular function in the hippocampus in vivo have been limited by its relative inaccessibility. Here we compared hippocampal and visual cortical neurovascular function in awake mice, using two photon imaging of individual neurons and vessels and measures of regional blood flow and haemoglobin oxygenation. We show that blood flow, blood oxygenation and neurovascular coupling were decreased in the hippocampus compared to neocortex, because of differences in both the vascular network and pericyte and endothelial cell function. Modelling oxygen diffusion indicates that these features of the hippocampal vasculature may restrict oxygen availability and could explain its sensitivity to damage during neurological conditions, including Alzheimer’s disease, where the brain’s energy supply is decreased. The hippocampus is particularly sensitive to hypoxia but it has been difficult to study blood flow in this region. Here the authors compare the neurovascular function of the hippocampus and cortex and in awake mice, and find differences associated with microvascular structure.

The hippocampus shrinks in late adulthood, leading to impaired memory and increased risk for dementia. Hippocampal and medial temporal lobe volumes are larger in higher-fit adults, and physical activity training increases hippocampal perfusion, but the extent to which aerobic exercise training can modify hippocampal volume in late adulthood remains unknown. Here we show, in a randomized controlled trial with 120 older adults, that aerobic exercise training increases the size of the anterior hippocampus, leading to improvements in spatial memory. Exercise training increased hippocampal volume by 2%, effectively reversing age-related loss in volume by 1 to 2 y. We also demonstrate that increased hippocampal volume is associated with greater serum levels of BDNF, a mediator of neurogenesis in the dentate gyrus. Hippocampal volume declined in the control group, but higher preintervention fitness partially attenuated the decline, suggesting that fitness protects against volume loss. Caudate nucleus and thalamus volumes were unaffected by the intervention. These theoretically important findings indicate that aerobic exercise training is effective at reversing hippocampal volume loss in late adulthood, which is accompanied by improved memory function.

Although the hippocampus has long been linked to planning, it has not been shown to be necessary for planning behavior. Using computational modeling and a new rat task that allows the quantification of planning behavior across many repeated trials, the authors report the first evidence that hippocampal inactivation impairs planning. Planning can be defined as action selection that leverages an internal model of the outcomes likely to follow each possible action. Its neural mechanisms remain poorly understood. Here we adapt recent advances from human research for rats, presenting for the first time an animal task that produces many trials of planned behavior per session, making multitrial rodent experimental tools available to study planning. We use part of this toolkit to address a perennially controversial issue in planning: the role of the dorsal hippocampus. Although prospective hippocampal representations have been proposed to support planning, intact planning in animals with damaged hippocampi has been repeatedly observed. Combining formal algorithmic behavioral analysis with muscimol inactivation, we provide causal evidence directly linking dorsal hippocampus with planning behavior. Our results and methods open the door to new and more detailed investigations of the neural mechanisms of planning in the hippocampus and throughout the brain.