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 (450 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
A curved elevation of gray matter extending the entire length of the floor of the temporal horn of the lateral ventricle (see also temporal lobe). The hippocampus proper, subiculum, and dentate gyrus constitute the hippocampal formation. Sometimes authors include the entorhinal cortex in the hippocampal formation.
Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.
Also known as: Ammon's Horn; Ammons Horn; Horn, Ammon's; Cornu Ammonis; Ammon Horn; Horn, Ammon; Hippocampus Proper; Hippocampus Propers.
Where it fits in the MeSH classification
- Broader topics
- Limbic System; Cerebral Cortex
- Narrower topics
- CA1 Region, Hippocampal; CA2 Region, Hippocampal; CA3 Region, Hippocampal; Dentate Gyrus; Fornix, Brain; Schaffer Collaterals
- See also
- Entorhinal Cortex; Perforant Pathway
Related concepts
- Gray Matter
- Temporal Horn
- Lateral Ventricle
- Temporal Lobe
- Dentate Gyrus
- Entorhinal Cortex
Research landscape
PubMed indexes 141,453 records tagged with the MeSH heading “Hippocampus” (counts retrieved 2026-10-29). 28,395 of them (20.1%) were published from 2020 onward, and the busiest period so far is 2010-2019 with 44,874 records.
Reviews account for 7,273 records (5.1%) and meta-analyses for 229. Randomized controlled trials number 464 (0.3%) as a share of all records on the topic. Randomized trials make up only a small share of this literature, so much of what is known comes from laboratory, observational or descriptive work.
Show the data
| Period | Records |
|---|---|
| through 1999 | 35,420 |
| 2000-2009 | 32,764 |
| 2010-2019 | 44,874 |
| 2020 onward | 28,395 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 7,273 | 5.1% |
| Meta-analyses | 229 | 0.2% |
| Randomized controlled trials | 464 | 0.3% |
Method: PubMed query "Hippocampus"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-29.
Reading the evidence in neuroscience
Neuroscience draws on tools with different strengths: cellular and animal work can manipulate circuits directly, while human imaging and electrophysiology observe the living brain at lower resolution. Small imaging studies are prone to false positives, and findings in animals do not always carry over to people. Clinical neurology and psychiatry rely on trials and cohort studies whose outcomes are often symptom scales. Check the species, the sample size, how the outcome was measured and whether results were replicated.
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 |
|---|---|---|---|---|
| Hippocampal theta sweeps indicate goal direction during navigation | 2026 | Research article Design not recorded in structured metadata | 8 | cc by PMID 42386950 · DOI · PMC13533849 |
| Repetitive neuronal activation regulates cellular maturation state via nuclear reprogramming | 2026 | Research article Design not recorded in structured metadata | 5 | cc by PMID 42469214 · DOI · PMC13379389 |
| Disrupted hippocampal theta-gamma coupling and spike-field coherence following experimental traumatic brain injury | 2026 | Research article Design not recorded in structured metadata | 3 | cc by PMID 42284087 · DOI · PMC13263039 |
Hippocampal theta sweeps indicate goal direction during navigation [1]
Abstract reading summary — source excerpts
- Opening excerpt
- Successful spatial navigation requires rapid evaluation of potential future trajectories.
- Closing excerpt
- Our findings identify hippocampal theta sweeps as neural substrates for online goal-directed planning.
- 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 (153 words)
Successful spatial navigation requires rapid evaluation of potential future trajectories. Hippocampal 'theta sweeps', the sequential activation of place cells within individual theta cycles, exhibit predictive dynamics within the ideal timeframe for this role. However, whether these sequences reflect movement-related variables, perceptual targets or more cognitive goal-directed planning remains unresolved. Using data from the 'Honeycomb' maze, which dissociates head, movement and goal directions, we found that theta sweeps form vectors toward remembered goal locations independent of the rat's movement or heading directions. Stronger goal modulation preceded correct navigational choices, establishing the relevance of theta sweeps for spatial planning. A hierarchical continuous attractor network with goal-oriented directional inputs reproduced these findings and made several nontrivial predictions, which we confirmed empirically. Sequential activity during immobility-related sharp-wave ripples was also goal directed and, therefore, more aligned with theta sweeps than with previously experienced trajectories. Our findings identify hippocampal theta sweeps as neural substrates for online goal-directed planning.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 42386950 · DOI · PMC13533849
Repetitive neuronal activation regulates cellular maturation state via nuclear reprogramming [2]
Abstract reading summary — source excerpts
- Opening excerpt
- Neural stimulation, such as electroconvulsive therapy (ECT) and repetitive transcranial magnetic stimulation (rTMS), is highly effective clinical intervention for a broad spectrum of psychiatric disorders, including depression and schizophrenia.
- Closing excerpt
- These findings demonstrate that chronically-repeated brain stimulation triggers plasticity of the cellular state, revealing a form of stimulus-regulated nuclear reprogramming with potential clinical utility.
- 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 (150 words)
Neural stimulation, such as electroconvulsive therapy (ECT) and repetitive transcranial magnetic stimulation (rTMS), is highly effective clinical intervention for a broad spectrum of psychiatric disorders, including depression and schizophrenia. However, their mechanism of action at the cellular level remains poorly understood. Here, we model ECT with repeated optogenetic neuronal stimulation in the mouse dentate gyrus, and observe ECT-relevant behavioral changes, including decreased depression-like behavior and increased locomotor activity. At the cellular level, we identify dematuration to a long-term stable state, persisting for more than one month, defined by changes in nuclear structure, gene expression patterns resembling the G2/M phase of the cell cycle, and altered neural coding of navigational information. Moreover, knockout of the G2/M master regulator Cyclin B attenuates some of behavioral and cellular effects. These findings demonstrate that chronically-repeated brain stimulation triggers plasticity of the cellular state, revealing a form of stimulus-regulated nuclear reprogramming with potential clinical utility.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 42469214 · DOI · PMC13379389
Disrupted hippocampal theta-gamma coupling and spike-field coherence following experimental traumatic brain injury [3]
Abstract reading summary — source excerpts
- Opening excerpt
- Traumatic brain injury (TBI) often results in persistent learning and memory deficits, likely due to disrupted hippocampal circuitry underlying these processes.
- Closing excerpt
- These results reveal physiological deficits across brain states that may contribute to TBI-associated learning and memory impairments and elucidate potential targets for future neuromodulation therapies.
- 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 (147 words)
Traumatic brain injury (TBI) often results in persistent learning and memory deficits, likely due to disrupted hippocampal circuitry underlying these processes. Precise temporal control of hippocampal neuronal activity is thought to be important for memory encoding and retrieval and is supported by oscillations that dynamically organize single-unit firing. Using high-density laminar electrophysiology, we found a loss of oscillatory power across CA1 lamina, with a profound, layer-specific reduction in theta-gamma phase-amplitude coupling in injured rats. Interneurons from injured animals were less strongly entrained to theta and gamma oscillations, but both interneurons and pyramidal cells from injured animals became more strongly entrained to theta during periods of high theta power. During quiet immobility, sharp-wave ripple amplitudes were lower in injured animals compared to shams. These results reveal physiological deficits across brain states that may contribute to TBI-associated learning and memory impairments and elucidate potential targets for future neuromodulation therapies.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 42284087 · DOI · PMC13263039
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 A systematic review and meta-analysis of magnetic resonance imaging measurement of structural volumes in posttraumatic stress disorder [4]
- Research article Novel genetic loci associated with hippocampal volume [5]
- Research article Systematic review and meta-analysis of standard vs selective temporal lobe epilepsy surgery [6]
- Research article How to build a cognitive map [7]
- Research article Chronic Stress-Associated Depressive Disorders: The Impact of HPA Axis Dysregulation and Neuroinflammation on the Hippocampus-A Mini Review [8]
- Research article A systematic review and meta-analysis of longitudinal hippocampal atrophy in healthy human ageing [9]
References
- Yu C, Ji Z, Ormond J, O'Keefe J, Burgess N. Hippocampal theta sweeps indicate goal direction during navigation. . 2026. PMID 42386950 · DOI · PMC13533849
- Murano T, Hagihara H, Tajinda K, Takao K, Takamiya Y, Katoh K, et al.. Repetitive neuronal activation regulates cellular maturation state via nuclear reprogramming. . 2026. PMID 42469214 · DOI · PMC13379389
- Adam CD, Mirzakhalili E, Gagnon KG, Cottone C, Arena JD, Ulyanova A, et al.. Disrupted hippocampal theta-gamma coupling and spike-field coherence following experimental traumatic brain injury. . 2026. PMID 42284087 · DOI · PMC13263039
- O'Doherty DC, Chitty KM, Saddiqui S, Bennett MR, Lagopoulos J. A systematic review and meta-analysis of magnetic resonance imaging measurement of structural volumes in posttraumatic stress disorder. Psychiatry Res. 2015. PMID 25735885 · DOI
- Hibar DP, Adams HHH, Jahanshad N, Chauhan G, Stein JL, Hofer E, et al.. Novel genetic loci associated with hippocampal volume. Nat Commun. 2017. PMID 28098162 · DOI · PMC5253632
- Josephson CB, Dykeman J, Fiest KM, Liu X, Sadler RM, Jette N, et al.. Systematic review and meta-analysis of standard vs selective temporal lobe epilepsy surgery. Neurology. 2013. PMID 23553475 · DOI
- Whittington JCR, McCaffary D, Bakermans JJW, Behrens TEJ. How to build a cognitive map. Nat Neurosci. 2022. PMID 36163284 · DOI
- Lei AA, Phang VWX, Lee YZ, Kow ASF, Tham CL, Ho YC, et al.. Chronic Stress-Associated Depressive Disorders: The Impact of HPA Axis Dysregulation and Neuroinflammation on the Hippocampus-A Mini Review. Int J Mol Sci. 2025. PMID 40243556 · DOI · PMC11988747
- Fraser MA, Shaw ME, Cherbuin N. A systematic review and meta-analysis of longitudinal hippocampal atrophy in healthy human ageing. Neuroimage. 2015. PMID 25800208 · DOI
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 2026-10-31; title, year and DOI matched.
- Review state
- automated source verified; no human expert review has been recorded yet.
- Version
- 1, last updated 2026-10-29.
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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.