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Science (New York, N.Y.) Jan 2020In 1904, Richard Semon introduced the term "engram" to describe the neural substrate for storing memories. An experience, Semon proposed, activates a subset of cells... (Review)
Review
In 1904, Richard Semon introduced the term "engram" to describe the neural substrate for storing memories. An experience, Semon proposed, activates a subset of cells that undergo off-line, persistent chemical and/or physical changes to become an engram. Subsequent reactivation of this engram induces memory retrieval. Although Semon's contributions were largely ignored in his lifetime, new technologies that allow researchers to image and manipulate the brain at the level of individual neurons has reinvigorated engram research. We review recent progress in studying engrams, including an evaluation of evidence for the existence of engrams, the importance of intrinsic excitability and synaptic plasticity in engrams, and the lifetime of an engram. Together, these findings are beginning to define an engram as the basic unit of memory.
Topics: Animals; Brain; Brain Chemistry; Humans; Memory Disorders; Mental Recall; Neurons
PubMed: 31896692
DOI: 10.1126/science.aaw4325 -
International Journal of Environmental... Aug 2021This research involved the participation of 3036 Chinese students in the first and second years of senior high school. The adolescents were active users of TikTok. The...
This research involved the participation of 3036 Chinese students in the first and second years of senior high school. The adolescents were active users of TikTok. The mediating effect of depression, anxiety, and stress between TikTok use disorder and memory loss was investigated. A forward and backward digit span test was applied to measure memory loss. Structural equation modeling (SEM) was established, and SPSS Amos was used for analysis. The results show a partial mediation effect of depression and anxiety between TikTok use disorder and forward digit span. A partial mediation effect of depression, anxiety, and stress between TikTok use disorder and backward digit span is also shown. These results also show gender differences. Attention should be given to male students, who have more depression, anxiety, and stress than female students; they also have more memory loss.
Topics: Adolescent; Anxiety; Anxiety Disorders; Depression; Female; Humans; Male; Memory Disorders; Social Media
PubMed: 34444569
DOI: 10.3390/ijerph18168820 -
The Lancet. Psychiatry Feb 2020Cognitive symptoms are common, and yet many who seek help for cognitive symptoms neither have, nor go on to develop, dementia. A proportion of these people are likely to...
Cognitive symptoms are common, and yet many who seek help for cognitive symptoms neither have, nor go on to develop, dementia. A proportion of these people are likely to have functional cognitive disorders, a subtype of functional neurological disorders, in which cognitive symptoms are present, associated with distress or disability, but caused by functional alterations rather than degenerative brain disease or another structural lesion. In this Review, we have systematically examined the prevalence and clinical associations of functional cognitive disorders, and related phenotypes, within the wider cognitive disorder literature. Around a quarter of patients presenting to memory clinics received diagnoses that might indicate the presence of functional cognitive disorders, which were associated with affective symptoms, negative self-evaluation, negative illness perceptions, non-progressive symptom trajectories, and linguistic and behavioural differences during clinical interactions. Those with functional cognitive disorder phenotypes are at risk of iatrogenic harm because of misdiagnosis or inaccurate prediction of future decline. Further research is imperative to improve diagnosis and identify effective treatments for functional cognitive disorders, and better understanding these phenotypes will also improve the specificity of diagnoses of prodromal degenerative brain disease.
Topics: Affective Symptoms; Attitude to Health; Cognition Disorders; Humans; Medically Unexplained Symptoms; Memory Disorders
PubMed: 31732482
DOI: 10.1016/S2215-0366(19)30405-5 -
Physiological Research Sep 2017Alzheimer's disease (AD) is a primary cause of dementia in the middle-aged and elderly worldwide. Animal models for AD are widely used to study the disease mechanisms as... (Review)
Review
Alzheimer's disease (AD) is a primary cause of dementia in the middle-aged and elderly worldwide. Animal models for AD are widely used to study the disease mechanisms as well as to test potential therapeutic agents for disease modification. Among the non-genetically manipulated neuroinflammation models for AD, lipopolysaccharide (LPS)-induced animal model is commonly used. This review paper aims to discuss the possible factors that influence rats' response following LPS injection. Factors such as dose of LPS, route of administration, nature and duration of exposure as well as age and gender of animal used should be taken into account when designing a study using LPS-induced memory impairment as model for AD.
Topics: Alzheimer Disease; Animals; Disease Models, Animal; Humans; Inflammation Mediators; Lipopolysaccharides; Memory Disorders; Rats
PubMed: 28406691
DOI: 10.33549/physiolres.933480 -
Nature Communications Mar 2021Aberrant regulation of microRNAs (miRNAs) has been implicated in the pathogenesis of Alzheimer's disease (AD), but most abnormally expressed miRNAs found in AD are not...
Aberrant regulation of microRNAs (miRNAs) has been implicated in the pathogenesis of Alzheimer's disease (AD), but most abnormally expressed miRNAs found in AD are not regulated by synaptic activity. Here we report that dysfunction of miR-135a-5p/Rock2/Add1 results in memory/synaptic disorder in a mouse model of AD. miR-135a-5p levels are significantly reduced in excitatory hippocampal neurons of AD model mice. This decrease is tau dependent and mediated by Foxd3. Inhibition of miR-135a-5p leads to synaptic disorder and memory impairments. Furthermore, excess Rock2 levels caused by loss of miR-135a-5p plays an important role in the synaptic disorder of AD via phosphorylation of Ser726 on adducin 1 (Add1). Blocking the phosphorylation of Ser726 on Add1 with a membrane-permeable peptide effectively rescues the memory impairments in AD mice. Taken together, these findings demonstrate that synaptic-related miR-135a-5p mediates synaptic/memory deficits in AD via the Rock2/Add1 signaling pathway, illuminating a potential therapeutic strategy for AD.
Topics: Alzheimer Disease; Animals; Cells, Cultured; Cytoskeletal Proteins; Disease Models, Animal; Hippocampus; Male; Maze Learning; Memory Disorders; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; MicroRNAs; Neurons; Phosphorylation; Signal Transduction; Synapses; rho-Associated Kinases; tau Proteins; Mice
PubMed: 33771994
DOI: 10.1038/s41467-021-22196-y -
Continuum (Minneapolis, Minn.) Jun 2015This article highlights the dissociable human memory systems of episodic, semantic, and procedural memory in the context of neurologic illnesses known to adversely... (Review)
Review
PURPOSE OF REVIEW
This article highlights the dissociable human memory systems of episodic, semantic, and procedural memory in the context of neurologic illnesses known to adversely affect specific neuroanatomic structures relevant to each memory system.
RECENT FINDINGS
Advances in functional neuroimaging and refinement of neuropsychological and bedside assessment tools continue to support a model of multiple memory systems that are distinct yet complementary and to support the potential for one system to be engaged as a compensatory strategy when a counterpart system fails.
SUMMARY
Episodic memory, the ability to recall personal episodes, is the subtype of memory most often perceived as dysfunctional by patients and informants. Medial temporal lobe structures, especially the hippocampal formation and associated cortical and subcortical structures, are most often associated with episodic memory loss. Episodic memory dysfunction may present acutely, as in concussion; transiently, as in transient global amnesia (TGA); subacutely, as in thiamine deficiency; or chronically, as in Alzheimer disease. Semantic memory refers to acquired knowledge about the world. Anterior and inferior temporal lobe structures are most often associated with semantic memory loss. The semantic variant of primary progressive aphasia (svPPA) is the paradigmatic disorder resulting in predominant semantic memory dysfunction. Working memory, associated with frontal lobe function, is the active maintenance of information in the mind that can be potentially manipulated to complete goal-directed tasks. Procedural memory, the ability to learn skills that become automatic, involves the basal ganglia, cerebellum, and supplementary motor cortex. Parkinson disease and related disorders result in procedural memory deficits. Most memory concerns warrant bedside cognitive or neuropsychological evaluation and neuroimaging to assess for specific neuropathologies and guide treatment.
Topics: Aged; Aged, 80 and over; Brain; Female; Humans; Male; Memory Disorders; Memory, Episodic; Memory, Short-Term; Middle Aged; Nervous System Diseases; Neuroimaging; Neuropsychological Tests
PubMed: 26039844
DOI: 10.1212/01.CON.0000466656.59413.29 -
PloS One 2020The GluD1 gene is associated with susceptibility for schizophrenia, autism, depression, and bipolar disorder. However, the function of GluD1 and how it is involved in...
The GluD1 gene is associated with susceptibility for schizophrenia, autism, depression, and bipolar disorder. However, the function of GluD1 and how it is involved in these conditions remain elusive. In this study, we generated a Grid1 gene-knockout (GluD1-KO) mouse line with a pure C57BL/6N genetic background and performed several behavioral analyses. Compared to a control group, GluD1-KO mice showed no significant anxiety-related behavioral differences, evaluated using behavior in an open field, elevated plus maze, a light-dark transition test, the resident-intruder test of aggression and sensorimotor gating evaluated by the prepulse inhibition test. However, GluD1-KO mice showed (1) higher locomotor activity in the open field, (2) decreased sociability and social novelty preference in the three-chambered social interaction test, (3) impaired memory in contextual, but not cued fear conditioning tests, and (4) enhanced depressive-like behavior in a forced swim test. Pharmacological studies revealed that enhanced depressive-like behavior in GluD1-KO mice was restored by the serotonin reuptake inhibitors imipramine and fluoxetine, but not the norepinephrine transporter inhibitor desipramine. In addition, biochemical analysis revealed no significant difference in protein expression levels, such as other glutamate receptors in the synaptosome and postsynaptic densities prepared from the frontal cortex and the hippocampus. These results suggest that GluD1 plays critical roles in fear memory, sociability, and depressive-like behavior.
Topics: Animals; Anxiety; Behavior, Animal; Depression; Fear; Glutamate Dehydrogenase; Interpersonal Relations; Male; Memory Disorders; Mice; Mice, Inbred C57BL; Mice, Knockout; Motor Activity; Social Behavior Disorders
PubMed: 32078638
DOI: 10.1371/journal.pone.0229288 -
Proceedings of the Japan Academy.... 2020Memory retrieval is not a passive process. When a memory is retrieved, the retrieved memory is destabilized, similar to short-term memory just after learning, and... (Review)
Review
Memory retrieval is not a passive process. When a memory is retrieved, the retrieved memory is destabilized, similar to short-term memory just after learning, and requires memory reconsolidation to re-stabilize the memory. Recent studies characterizing destabilization and reconsolidation showed that a retrieved memory is not always destabilized and that there are boundary conditions that determine the induction of destabilization and reconsolidation according to certain parameters, such as the duration of retrieval and the memory strength and age. Moreover, the reconsolidation of contextual fear memory is not independent of memory extinction; rather, these memory processes interact with each other. There is an increasing number of findings suggesting that destabilization following retrieval facilitates the modification, weakening, or strengthening of the original memory, and the resultant updated memory is stabilized through reconsolidation. Reconsolidation could be targeted therapeutically to improve emotional disorders such as post-traumatic stress disorder and phobia. Thus, this review summarizes recent findings to understand the mechanisms and function of reconsolidation.
Topics: Animals; Brain; Extinction, Psychological; Fear; Humans; Memory Consolidation; Memory Disorders; Mental Disorders; Phobic Disorders; Signal Transduction; Stress Disorders, Traumatic
PubMed: 32161213
DOI: 10.2183/pjab.96.008 -
Aging Oct 2018
Topics: Age Factors; Animals; Cognition; Cognition Disorders; Estrogen Replacement Therapy; Female; Humans; Memory; Memory Disorders; Menopause; Nootropic Agents; Risk Factors; Sex Factors
PubMed: 30321139
DOI: 10.18632/aging.101596 -
Critical Care (London, England) Dec 2019Memory gaps in intensive care unit (ICU) survivors are associated with psychiatric disorders. The ICU diaries improve the patient's factual memory of the ICU, but it is... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Memory gaps in intensive care unit (ICU) survivors are associated with psychiatric disorders. The ICU diaries improve the patient's factual memory of the ICU, but it is not clear if they reduce the incidence of psychiatric disorders in patients and relatives after hospital discharge. The aim of this study is to evaluate the literature on the effect of ICU diaries for patients admitted in ICU and their relatives.
METHODS
Two authors independently searched the online databases PubMed, OVID, Embase, EBSCO host, and PsycINFO from inception to July 2019. Studies were included if the intervention group (ICU diary) was compared with a group with no diaries and the sample was comprised patients ≥ 18 years old admitted in the ICU for more than 24 h and their relatives. Randomized clinical trials, observational studies, letter with original data, and abstracts were included, irrespective of the language. The search was not limited by any specific outcome. Review articles, commentaries, editorials, and studies without a control group were excluded. Structured tools were used to assess the methodological quality ("Risk Of Bias In Non-randomized Studies of Interventions (ROBINS-I)" for cohort studies and the "Cochrane Risk of Bias tool" for included RCTs and before/after studies). A random-effects model was employed considering the anticipated variability between the studies.
RESULTS
Seven hundred eighty-five titles were identified for screening. Two additional studies were selected after a reference search, and after a full-text review, a total of 12 studies were included. When pooling the results, ICU diary was associated with lower risk of depression (RR 0.41, 95% CI 0.23-0.75) and better quality of life (10.3 points higher in SF-36 general health score, 95% CI 0.79-19.8), without a decrease in anxiety or post-traumatic stress disorder (PTSD). For the relatives receiving an ICU diary, there was no difference in the incidence of PTSD, anxiety, or depression.
CONCLUSION AND RELEVANCE
This systematic review and meta-analysis supports the use of ICU diaries to reduce the risk of depression and preserve the quality of life of patients after ICU admission. ICU diaries do not seem to have any beneficial effect on the relatives of the patients.
TRIAL REGISTRATION
PROSPERO, CRD42019136639.
Topics: Critical Illness; Diaries as Topic; Family; Humans; Intensive Care Units; Memory Disorders; Outcome Assessment, Health Care; Patients; Stress Disorders, Post-Traumatic; Survivors
PubMed: 31842929
DOI: 10.1186/s13054-019-2678-0