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Dietary Lutein and Cognitive Function in Adults: A Meta-Analysis of Randomized Controlled Trials.
Li, J, Abdel-Aal, EM
Molecules (Basel, Switzerland). 2021;(19)
Abstract
Emerging literature suggests that dietary lutein may have important functions in cognitive health, but there is not enough data to substantiate its effects in human cognition. The current study was intended to determine the overall effect of lutein on the main domains of cognition in the adult population based on available placebo randomized-controlled trials. Literature searches were conducted in PubMed, AGRICOLA, Scopus, MEDLINE, and EMBASE on 14 November 2020. The effect of lutein on complex attention, executive function and memory domains of cognition were assessed by using an inverse-variance meta-analysis of standardized mean differences (SMD) (Hedge's g method). Dietary lutein was associated with slight improvements in cognitive performance in complex attention (SMD 0.02, 95% CI -0.27 to 0.31), executive function (SMD 0.13, 95% CI -0.26 to 0.51) and memory (SMD 0.03, 95% CI -0.26 to 0.32), but its effect was not significant. Change-from-baseline analysis revealed that lutein consumption could have a role in maintaining cognitive performance in memory and executive function. Although dietary lutein did not significantly improve cognitive performance, the evidence across multiple studies suggests that lutein may nonetheless prevent cognitive decline, especially executive function. More intervention studies are needed to validate the role of lutein in preventing cognitive decline and in promoting brain health.
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A Narrative Review of Handgrip Strength and Cognitive Functioning: Bringing a New Characteristic to Muscle Memory.
Shaughnessy, KA, Hackney, KJ, Clark, BC, Kraemer, WJ, Terbizan, DJ, Bailey, RR, McGrath, R
Journal of Alzheimer's disease : JAD. 2020;(4):1265-1278
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Abstract
BACKGROUND Measures of handgrip strength have not only emerged as a clinically viable screening tool for determining risk for morbidity, functional disability, and early mortality, but also for helping to identify cognitive deficits. However, the phenomena that links low handgrip strength with cognitive decline remains unclear. The role of the muscular and neural systems, and their adaptations to muscle strengthening activities over the life course, may provide important information for how age-related changes to muscle mass, strength, and neural capacity influence cognition. Moreover, disentangling how handgrip strength and cognitive function are associated may help to inform healthcare providers working with aging adults and guide targeted interventions aiming to preserve muscle and cognitive functioning. OBJECTIVE To 1) highlight and summarize evidence examining the associations of handgrip strength and cognitive functioning, and 2) provide directions for future research in this area. METHODS Articles from the PubMed database were searched from November 2018-May 2019. The search term algorithm, inclusion and exclusion criteria were pre-specified by investigators. RESULTS Several cross-sectional and longitudinal studies have revealed that measures of handgrip strength were associated with cognitive declines regardless of age demographics and the presence of comorbidities. CONCLUSION Handgrip strength can be used in clinical and epidemiological settings for helping to determine the onset and progression of cognitive impairment. Future research should continue to examine how handgrip strength and cognitive function are linked.
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Can Slow-Wave Sleep Enhancement Improve Memory? A Review of Current Approaches and Cognitive Outcomes.
Zhang, Y, Gruber, R
The Yale journal of biology and medicine. 2019;(1):63-80
Abstract
Slow-wave sleep (SWS) is involved in the overnight consolidation of declarative memories. Recent efforts using auditory stimulation, slow-oscillatory transcranial direct current stimulation (so-tDCS), and pharmacological agents have targeted sleep slow-waves as a method for enhancing cognitive performance. However, no studies thus far have integrated current evidence to provide a preliminary review of the effects of SWS enhancement on memory and other cognitive outcomes. The objective of this review was to synthesize the results of recent experimental studies that have used auditory stimulation, electrical, and pharmacological methods to boost both SWS and cognitive performance. A systematic review was done to identify and consolidate all currently existing empirical studies in this area. We found that each stimulation method could enhance slow-wave power and/or SWS duration in human subjects. Closed-loop, in-phase auditory stimulation enhanced verbal declarative memory in healthy adults. Electrical stimulation using so-tDCS showed some efficacy in promoting verbal declarative memory, picture recognition memory, and location memory. Interleukin-6 and sodium oxybate enhanced declarative verbal memory, while tiagabine and sodium oxybate improved some non-memory measures of cognitive performance. There is some evidence that so-tDCS can also improve certain cognitive outcomes in clinical populations. Overall, future studies should recruit larger sample sizes drawn from more diverse populations, and determine clinical significance and effect sizes of each enhancement methodology.
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Temporal lobe surgery and memory: Lessons, risks, and opportunities.
Bauman, K, Devinsky, O, Liu, AA
Epilepsy & behavior : E&B. 2019;(Pt A):106596
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Abstract
Careful study of the clinical outcomes of temporal lobe epilepsy (TLE) surgery has greatly advanced our knowledge of the neuroanatomy of human memory. After early cases resulted in profound amnesia, the critical role of the hippocampus and associated medial temporal lobe (MTL) structures to declarative memory became evident. Surgical approaches quickly changed to become unilateral and later, to be more precise, potentially reducing cognitive morbidity. Neuropsychological studies following unilateral temporal lobe resection (TLR) have challenged early models, which simplified the lateralization of verbal and visual memory function. Diagnostic tests, including intracarotid sodium amobarbital procedure (WADA), structural magnetic resonance imaging (MRI), and functional neuroimaging (functional MRI (fMRI), positron emission tomography (PET), and single-photon emission computed tomography (SPECT)), can more accurately lateralize and localize epileptogenic cortex and predict memory outcomes from surgery. Longitudinal studies have shown that memory may even improve in seizure-free patients. From 70 years of experience with epilepsy surgery, we now have a richer understanding of the clinical, neuroimaging, and surgical predictors of memory decline-and improvement-after TLR. "Special Issue: Epilepsy & Behavior's 20th Anniversary".
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The Impact of Epicatechin on Human Cognition: The Role of Cerebral Blood Flow.
Haskell-Ramsay, CF, Schmitt, J, Actis-Goretta, L
Nutrients. 2018;(8)
Abstract
Epicatechin is a monomeric flavanol found in food sources such as tea, apples, berries and cocoa. A number of large-scale epidemiological studies have demonstrated an association between the consumption of these foods and cognitive function, as well as improved blood flow. The aim of this review is to summarise the evidence from intervention studies to clarify the effect of epicatechin on cognition and to consider the role of increased cerebral blood flow as a mechanism for any effects. The effects of epicatechin as consumed in cocoa are, therefore, reviewed here as this represents the only dietary source where it is purported to be the major active component. Our main findings are that a) the positive modulation of tasks that involve memory, executive function and processing speed in older adults; b) the cognitive benefits are more often shown in studies containing more than 50 mg epicatechin/day; and c) all studies with a duration of 28 days or longer in populations >50 years old demonstrate a cognitive improvement. However, as highlighted by this review, it is not currently possible to attribute effects solely to epicatechin without consideration of synergies. In order to overcome this issue, further studies examining the cognitive effects of epicatechin in isolation are required. The role of cerebral blood flow also requires further investigation through simultaneous measurement alongside cognitive function.
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Docosahexaenoic acid and adult memory: a systematic review and meta-analysis.
Yurko-Mauro, K, Alexander, DD, Van Elswyk, ME
PloS one. 2015;(3):e0120391
Abstract
INTRODUCTION Subjective memory complaints are common with aging. Docosahexaenoic acid (DHA; 22:6 n-3) is a long-chain polyunsaturated fatty acid (LCPUFA) and an integral part of neural membrane phospholipids that impacts brain structure and function. Past research demonstrates a positive association between DHA plasma status/dietary intake and cognitive function. OBJECTIVES The current meta-analysis was designed to determine the effect of DHA intake, alone or combined with eicosapentaenoic acid (EPA; 20:5 n-3), on specific memory domains: episodic, working, and semantic in healthy adults aged 18 years and older. A secondary objective was to systematically review/summarize the related observational epidemiologic literature. METHODS A systematic literature search of clinical trials and observational studies that examined the relationship between n-3 LCPUFA on memory outcomes in healthy adults was conducted in Ovid MEDLINE and EMBASE databases. Studies of subjects free of neurologic disease at baseline, with or without mild memory complaints (MMC), were included. Random effects meta-analyses were conducted to generate weighted group mean differences, standardized weighted group mean differences (Hedge's g), z-scores, and p-values for heterogeneity comparing DHA/EPA to a placebo. A priori sub-group analyses were conducted to evaluate the effect of age at enrollment, dose level, and memory type tested. RESULTS Episodic memory outcomes of adults with MMC were significantly (P<.004) improved with DHA/EPA supplementation. Regardless of cognitive status at baseline, > 1 g/day DHA/EPA improved episodic memory (P<.04). Semantic and working memory changes from baseline were significant with DHA but no between group differences were detected. Observational studies support a beneficial association between intake/blood levels of DHA/EPA and memory function in older adults. CONCLUSION DHA, alone or combined with EPA, contributes to improved memory function in older adults with mild memory complaints.
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Untangling the two-way signalling route from synapses to the nucleus, and from the nucleus back to the synapses.
Nonaka, M, Fujii, H, Kim, R, Kawashima, T, Okuno, H, Bito, H
Philosophical transactions of the Royal Society of London. Series B, Biological sciences. 2014;(1633):20130150
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During learning and memory, it has been suggested that the coordinated electrical activity of hippocampal neurons translates information about the external environment into internal neuronal representations, which then are stored initially within the hippocampus and subsequently into other areas of the brain. A widely held hypothesis posits that synaptic plasticity is a key feature that critically modulates the triggering and the maintenance of such representations, some of which are thought to persist over time as traces or tags. However, the molecular and cell biological basis for these traces and tags has remained elusive. Here, we review recent findings that help clarify some of the molecular and cellular mechanisms critical for these events, by untangling a two-way signalling crosstalk route between the synapses and the neuronal soma. In particular, a detailed interrogation of the soma-to-synapse delivery of immediate early gene product Arc/Arg3.1, whose induction is triggered by heightened synaptic activity in many brain areas, teases apart an unsuspected 'inverse' synaptic tagging mechanism that likely contributes to maintaining the contrast of synaptic weight between strengthened and weak synapses within an active ensemble.
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[Contribution of omega-3 fatty acids for memory and cognitive function].
Waitzberg, DL, Garla, P
Nutricion hospitalaria. 2014;(3):467-77
Abstract
INTRODUCTION A decline in memory and cognitive function is considered to be a normal consequence of aging. Polyunsaturated omega-3 fatty acids are increasingly proposed as dietary supplements with the ability to reduce the risk of cognitive decline, including Alzheimer's disease (AD). AIM: To study the effect of omega-3 on cognitive decline through the review of recent observational, interventional, and experimental studies. METHODS We conducted a Pubmed, Medline, Cochrane and Embase search for epidemiological and clinical studies in the international literature using combinations of the following keywords: "Alzheimer's disease", "mild cognitive impairment", "cognitive function", "dietary factors", "omega-3 fatty acids", "EPA and DHA". CONCLUSIONS Studies have shown the protective role of omega-3 fatty acids in mild cognitive impairment, dementia, and the risk and progression of Alzheimer's disease in the elderly. Further studies are needed to understand the mechanism of action of omega-3 fatty acids on cognition. Doses, composition of EPA and DHA capsules and time of supplementation should be explored.
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Systematic review of clinical trials assessing pharmacological properties of Salvia species on memory, cognitive impairment and Alzheimer's disease.
Miroddi, M, Navarra, M, Quattropani, MC, Calapai, F, Gangemi, S, Calapai, G
CNS neuroscience & therapeutics. 2014;(6):485-95
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Salvia officinalis L. and Salvia lavandulaefolia L. have a longstanding use as traditional herbal remedies that can enhance memory and improve cognitive functions. Pharmacological actions of S. officinalis and S. lavandulaefolia on healthy subjects and on patients suffering of cognitive decline have been investigated. Aim of this review was to summarize published clinical trials assessing effectiveness and safety of S. officinalis and S. lavandulaefolia in the enhancement of cognitive performance in healthy subjects and neurodegenerative illnesses. Furthermore, to purchase a more complete view on safety of S. officinalis and S. lavandulaefolia, we collected and discussed articles regarding toxicity and adverse reactions. Eight clinical studies investigating on acute effects of S. officinalis on healthy subjects were included in the review. Six studies investigated on the effects of S. officinalis and S. lavandaeluaefolia on cognitive performance in healthy subjects. The two remaining were carried out to study the effects of sage on Azheimer's disease. Our review shows that S. officinalis and S. lavandulaefolia exert beneficial effects by enhancing cognitive performance both in healthy subjects and patients with dementia or cognitive impairment and is safe for this indication. Unfortunately, promising beneficial effects are debased by methodological issues, use of different herbal preparations (extracts, essential oil, use of raw material), lack of details on herbal products used. We believe that sage promising effects need further higher methodological standard clinical trials.
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Mechanisms of heterosynaptic metaplasticity.
Hulme, SR, Jones, OD, Raymond, CR, Sah, P, Abraham, WC
Philosophical transactions of the Royal Society of London. Series B, Biological sciences. 2014;(1633):20130148
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Synaptic plasticity is fundamental to the neural processes underlying learning and memory. Interestingly, synaptic plasticity itself can be dynamically regulated by prior activity, in a process termed 'metaplasticity', which can be expressed both homosynaptically and heterosynaptically. Here, we focus on heterosynaptic metaplasticity, particularly long-range interactions between synapses spread across dendritic compartments, and review evidence for intracellular versus intercellular signalling pathways leading to this effect. Of particular interest is our previously reported finding that priming stimulation in stratum oriens of area CA1 in the hippocampal slice heterosynaptically inhibits subsequent long-term potentiation and facilitates long-term depression in stratum radiatum. As we have excluded the most likely intracellular signalling pathways that might mediate this long-range heterosynaptic effect, we consider the hypothesis that intercellular communication may be critically involved. This hypothesis is supported by the finding that extracellular ATP hydrolysis, and activation of adenosine A2 receptors are required to induce the metaplastic state. Moreover, delivery of the priming stimulation in stratum oriens elicited astrocytic calcium responses in stratum radiatum. Both the astrocytic responses and the metaplasticity were blocked by gap junction inhibitors. Taken together, these findings support a novel intercellular communication system, possibly involving astrocytes, being required for this type of heterosynaptic metaplasticity.