Definition and research guide
This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.
Content available: 3 complete abstracts (503 words), 9 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.
Definition
Complex mental function having four distinct phases: (1) memorizing or learning, (2) retention, (3) recall, and (4) recognition. Clinically, it is usually subdivided into immediate, recent, and remote memory.
Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.
Where it fits in the MeSH classification
- Broader topics
- Learning
- Narrower topics
- Deja Vu; Memory, Episodic; Memory, Long-Term; Memory, Short-Term; Mental Recall; Recognition, Psychology; Repetition Priming; Retention, Psychology; Spatial Memory
Research landscape
PubMed indexes 168,218 records tagged with the MeSH heading “Memory” (counts retrieved 2026-10-31). 31,462 of them (18.7%) were published from 2020 onward, and the busiest period so far is 2010-2019 with 62,988 records.
Reviews account for 13,656 records (8.1%) and meta-analyses for 1,248. Randomized controlled trials number 7,779 (4.6%) as a share of all records on the topic.
Show the data
| Period | Records |
|---|---|
| through 1999 | 35,328 |
| 2000-2009 | 38,440 |
| 2010-2019 | 62,988 |
| 2020 onward | 31,462 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 13,656 | 8.1% |
| Meta-analyses | 1,248 | 0.7% |
| Randomized controlled trials | 7,779 | 4.6% |
Method: PubMed query "Memory"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-31.
Reading the evidence in psychiatry and psychology
Research on mental health and behaviour relies on questionnaires, interviews and rating scales rather than physical measurements, so how a condition was defined and measured shapes every result. Many studies are observational or small, placebo responses can be large, and findings in one group or culture may not carry over to another. Nothing on this page is advice about diagnosis or treatment; anyone worried about their mental health should talk to a qualified clinician. Check how outcomes were measured, who took part and how long they were followed.
Evidence from open-access studies
These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.
| Study / authors | Year | Source label / design | Europe PMC citations | Licence / source |
|---|---|---|---|---|
| Developmental Scarcity Induces Sex Differences in Social Recognition and CA2 Perineuronal Nets | 2026 | Research article Design not recorded in structured metadata | 2 | cc by PMID 42692858 · DOI · PMC13592735 |
| Remembering the "when": Hebbian memory models for the time of past events | 2026 | Research article Design not recorded in structured metadata | 2 | cc by PMID 42520083 · DOI · PMC13436827 |
| Experience reorganizes content-specific memory traces in macaques | 2026 | Research article Design not recorded in structured metadata | 2 | cc by PMID 42527550 · DOI · PMC13433320 |
Developmental Scarcity Induces Sex Differences in Social Recognition and CA2 Perineuronal Nets [1]
Abstract reading summary — source excerpts
- Opening excerpt
- Early-life adversity (ELA) has a lasting negative impact on social behavior in both humans and rodents.
- Closing excerpt
- Focal degradation of the extracellular matrix in the CA2 region restored social recognition function in adult males previously subjected to early stress, suggesting that the effects of developmental adversity may be improved by targeted intervention in adulthood.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (148 words)
Early-life adversity (ELA) has a lasting negative impact on social behavior in both humans and rodents. Sex differences exist in functional outcomes of postnatal stress, but underlying mechanisms remain incompletely explored. Using the limited bedding and nesting paradigm, a mouse model of developmental scarcity, we found sex differences in social behavior with adult males showing impaired social recognition and adult females showing intact social recognition with enhanced social novelty preference. Perineuronal nets (PNNs), specialized extracellular matrix structures, are known to inhibit developmental plasticity and are concentrated in the CA2 region of the hippocampus in adulthood. We found higher intensity of CA2 PNNs in adult males, but not adult females, after ELA. Focal degradation of the extracellular matrix in the CA2 region restored social recognition function in adult males previously subjected to early stress, suggesting that the effects of developmental adversity may be improved by targeted intervention in adulthood.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 42692858 · DOI · PMC13592735
Remembering the "when": Hebbian memory models for the time of past events [2]
Abstract reading summary — source excerpts
- Opening excerpt
- Humans and animals can remember how long ago specific events happened.
- Closing excerpt
- Our study shows that remembering the "when" can be implemented by many biologically plausible mechanisms and that carefully designed experiments are needed to pin down the actual neural implementation of the memory for the time of past events in different species.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (199 words)
Humans and animals can remember how long ago specific events happened. Little is known about the neural mechanisms that enable remembering the "when" of memories stored for long durations in the episodic memory system - in contrast to interval-timing on the order of seconds and minutes. Based on a systematic exploration of neural coding, association and retrieval schemes, we develop model classes that span the space of possible mechanisms for the reconstruction of the time of past events. In concrete examples we show how network architecture, Hebbian plasticity, synaptic pruning or systems consolidation allow the retrieval of the time of past events. In a simulation, we demonstrate how these mechanisms would enable food-caching animals such as corvids to remember what they cached, where, and how long ago. To dissociate different hypotheses, we propose three kinds of novel, non-verbal experiments that can be run with humans and animals. Our simulations predict the experimental results for different classes of models. Our study shows that remembering the "when" can be implemented by many biologically plausible mechanisms and that carefully designed experiments are needed to pin down the actual neural implementation of the memory for the time of past events in different species.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 42520083 · DOI · PMC13436827
Experience reorganizes content-specific memory traces in macaques [3]
Abstract reading summary — source excerpts
- Opening excerpt
- Memory formation relies on the reorganization of neural activity patterns during experience that persist in subsequent sleep.
- Closing excerpt
- These findings reveal rapid organization and stabilization of neural activity in the primate brain, suggesting potential mechanisms for balancing learning with memory linking and durability.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (156 words)
Memory formation relies on the reorganization of neural activity patterns during experience that persist in subsequent sleep. How these processes promote learning while preserving established memories remains unclear. Here we recorded neural ensemble activity from the hippocampal and associated regions in freely moving macaques as they recalled item sequences presented that day ('new'), 1 day earlier ('recent') or more than 2 weeks earlier ('old'). Cell assemblies biased for old sequences showed less drift, greater network connectivity and stronger sleep reactivation than new-biased assemblies. Pairs of old and recent assemblies formed persistent task-to-sleep coupling ('metassemblies'), unlike new assembly pairs, and these assembly pairs showed longer interactions over time than the new pairs. In the hippocampus, the propensity for superficial and deep CA1 pyramidal cells to form integrated assemblies increased with memory age. These findings reveal rapid organization and stabilization of neural activity in the primate brain, suggesting potential mechanisms for balancing learning with memory linking and durability.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 42527550 · DOI · PMC13433320
Key reviews and meta-analyses
The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.
- Research article Working Memory Training Does Not Improve Performance on Measures of Intelligence or Other Measures of "Far Transfer": Evidence From a Meta-Analytic Review [4]
- Research article Effects of physical activity on executive functions, attention and academic performance in preadolescent children: a meta-analysis [5]
- Research article Anxiety and working memory capacity: A meta-analysis and narrative review [6]
- Research article The effect of testing versus restudy on retention: a meta-analytic review of the testing effect [7]
- Research article Cognitive training for attention-deficit/hyperactivity disorder: meta-analysis of clinical and neuropsychological outcomes from randomized controlled trials [8]
- Research article The effects of acute stress on episodic memory: A meta-analysis and integrative review [9]
Full-text reviews on EvidenceLib
Open-access review articles about this topic, reproduced in full with authors, licence and references.
Stress resilience in plants: the complex interplay between heat stress memory and resetting
Tobias Staacke, Bernd Mueller‐Roeber, Salma Balazadeh · The New Phytologist 2025 · CC BY 4.0
The Frontal Aslant Tract: A Systematic Review for Neurosurgical Applications
Emanuele La Corte, Daniela Eldahaby, Elena Greco et al. · Frontiers in Neurology 2021 · CC BY 4.0
References
- Waters RC, Gore IR, Brown CJ, Skweres-Gilmartin AL, Rathaur AB, Gould E. Developmental Scarcity Induces Sex Differences in Social Recognition and CA2 Perineuronal Nets. . 2026. PMID 42692858 · DOI · PMC13592735
- Brea J, Modirshanechi A, Iatropoulos G, Gerstner W. Remembering the "when": Hebbian memory models for the time of past events. . 2026. PMID 42520083 · DOI · PMC13436827
- Abbaspoor S, Aljishi A, Hoffman KL. Experience reorganizes content-specific memory traces in macaques. . 2026. PMID 42527550 · DOI · PMC13433320
- Melby-Lervåg M, Redick TS, Hulme C. Working Memory Training Does Not Improve Performance on Measures of Intelligence or Other Measures of "Far Transfer": Evidence From a Meta-Analytic Review. Perspect Psychol Sci. 2016. PMID 27474138 · DOI · PMC4968033
- de Greeff JW, Bosker RJ, Oosterlaan J, Visscher C, Hartman E. Effects of physical activity on executive functions, attention and academic performance in preadolescent children: a meta-analysis. J Sci Med Sport. 2018. PMID 29054748 · DOI
- Moran TP. Anxiety and working memory capacity: A meta-analysis and narrative review. Psychol Bull. 2016. PMID 26963369 · DOI
- Rowland CA. The effect of testing versus restudy on retention: a meta-analytic review of the testing effect. Psychol Bull. 2014. PMID 25150680 · DOI
- Cortese S, Ferrin M, Brandeis D, Buitelaar J, Daley D, Dittmann RW, et al.. Cognitive training for attention-deficit/hyperactivity disorder: meta-analysis of clinical and neuropsychological outcomes from randomized controlled trials. J Am Acad Child Adolesc Psychiatry. 2015. PMID 25721181 · DOI · PMC4382075
- Shields GS, Sazma MA, McCullough AM, Yonelinas AP. The effects of acute stress on episodic memory: A meta-analysis and integrative review. Psychol Bull. 2017. PMID 28368148 · DOI · PMC5436944
About this article
- Sources
- NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
- Verification
- Every reference was resolved against PubMed on 2026-11-04; title, year and DOI matched.
- Review state
- automated source verified; no human expert review has been recorded yet.
- Version
- 1, last updated 2026-11-04.
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Evidence strength
EvidenceHelix's computed view of the study designs behind this topic: how common meta-analyses, randomized trials and reviews are, how recent the literature is, and a plain-language reading. It describes the design mix of the literature. It is not a quality appraisal of any study, and it is not medical advice.