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Memory transfer

Memory transfer, also known as memory transplantation, refers to the experimental process of conveying learned behaviors or memory traces from a donor organism to a recipient organism, typically through the administration of biological molecules such as RNA extracted from the donor's nervous system.^[1] This concept challenges traditional views of memory as solely synaptic, suggesting instead that molecular or epigenetic mechanisms may encode and transmit memory-like effects.^[2] While early attempts in the mid-20th century were highly controversial and largely unreplicated, more recent studies in invertebrate models have provided empirical evidence for such transfer in specific forms of non-declarative memory, such as sensitization.^[1] The origins of memory transfer research trace back to the 1950s and 1960s, when biopsychologist James V. McConnell conducted pioneering experiments with planarians (flatworms), demonstrating that untrained planarians exhibited conditioned responses after consuming trained counterparts or receiving injections of RNA extracts from them.^[1] McConnell's work, funded by over $150,000 in grants from 1959 to 1964 and published in journals like the Journal of Comparative and Physiological Psychology, hypothesized that RNA served as a "memory molecule" capable of transferring learning across organisms.^[1] This sparked a wave of over 247 studies involving approximately 200 research teams and 23 species, including rats and octopuses, with notable support from psychologists like Donald Hebb and Karl Pribram.^[1] However, by the late 1960s, independent replications failed, leading to widespread skepticism; for instance, four labs reported initial successes with rat avoidance learning in 1965 publications in Science and Nature, but subsequent efforts could not confirm the results.^[1] In the 1960s, pharmacologist Georges Ungar advanced the field by isolating purported memory molecules, such as scotophobin from trained rats' brains, which he claimed transferred dark-avoidance behavior when injected into naive rats.^[3] Ungar's experiments, which gained significant attention and theoretical backing, posited that peptides or small molecules encoded specific memories, influencing hundreds of follow-up studies despite methodological critiques.^[3] These efforts ultimately faltered due to irreproducibility and inability to purify consistent active compounds, contributing to the decline of chemical memory transfer research by the 1970s.^[3] Contemporary research revived interest in 2018, when neuroscientists at UCLA, led by David L. Glanzman, successfully transferred a form of long-term sensitization memory between marine snails (Aplysia californica) by injecting total RNA extracted from the nervous systems of sensitized donor snails into untrained recipients.^[2] In the study, published in eNeuro, recipients displayed enhanced defensive siphon-withdrawal reflexes lasting up to 24 hours, mimicking the donors' trained response to tail shocks, and this effect persisted even after synaptic disruption, implicating an epigenetic engram carried by RNA.^[2] Subsequent studies, such as 2021 research in C. elegans nematodes, have further shown RNA-mediated transfer of avoidance memories via extracellular particles.^[4] This finding supports the idea that memory traces can be molecularly encoded outside traditional synaptic sites, though it applies specifically to implicit, non-associative learning in invertebrates and remains debated for broader applicability.^[2]

History

Origins in early neuroscience

The conceptual foundations of memory transfer trace back to early 20th-century neuroscience, where researchers began exploring memory as a physical, potentially transferable entity within biological systems. In 1904, German zoologist Richard Semon introduced the term "mneme" in his book Die Mneme, proposing that memory operates through enduring physiochemical modifications in living cells, termed engrams, which serve as latent traces of experiences. Semon envisioned these engrams as hereditary chemical imprints embedded in the "irritable substance" of cells, suggesting that stimuli induce permanent, though initially dormant, changes that could be reactivated and even passed across generations via Lamarckian inheritance mechanisms. This framework linked memory storage to cellular chemistry, laying groundwork for later ideas that such traces might be extractable or transferable beyond neural structures.^[5]^[6] Building on Semon's engram concept, American psychologist Karl Lashley advanced the search for memory's physical basis during the 1920s and 1940s through extensive lesion studies in rats, aiming to localize the engram as a distributed trace rather than a discrete site. In works such as Brain Mechanisms and Intelligence (1929), Lashley demonstrated that maze-learning abilities persisted despite surgical removal of various cortical regions, leading him to formulate principles of equipotentiality—where different brain areas could support the same function—and mass action, where memory performance scaled with overall cortical mass rather than specific locales. These findings implied that engrams were not confined to isolated neural circuits but spread across the cortex as interconnected physical modifications, challenging localization theories and opening speculative pathways for memory as a transferable, non-localized entity without detailing chemical mechanisms. Lashley's unsuccessful quest, summarized in his 1950 lecture "In Search of the Engram," underscored the complexity of memory traces, influencing subsequent hypotheses on their potential mobility.^[7]^[8] Initial empirical hints of memory transfer emerged in the 1950s through experiments on planarian flatworms by American psychologist James V. McConnell, who trained Dugesia dorotocephala worms using classical conditioning to associate a light stimulus with an electric shock, prompting avoidance responses like contractions or turns. McConnell and colleagues observed that when trained worms were decapitated and allowed to regenerate their heads—and thus their primitive nervous systems—the regenerated animals retained significant portions of the learned response, with retention rates up to 50-70% in some segments compared to controls. This persistence across regeneration suggested memory storage independent of the original neural architecture, potentially in non-neural tissues or diffusible substances. These findings were reported by McConnell, Jacobson, and Kimble (1959) in the Journal of Comparative and Physiological Psychology, titled "The Effects of Regeneration upon Retention of a Conditioned Response in the Planarian," arguing for a molecular basis for memory that could survive bodily reorganization and hint at transferability. This work prompted further investigations into direct transfer, such as cannibalism experiments published in 1962.^[9]^[10]

Mid-20th century experiments

In the 1960s, empirical research on memory transfer intensified with experiments involving the extraction and injection of brain RNA from trained animals into naive recipients to assess whether learned behaviors could be induced. Allan L. Jacobson and colleagues at the University of California, Los Angeles, conducted pioneering studies using rats in a two-choice discrimination maze, where animals were trained to prefer one arm over another based on visual cues and food rewards. RNA was extracted from the brains of trained donor rats (approximately 1.0 mg per gram of tissue) and injected intraperitoneally into naive recipient rats shortly before testing in the unrewarded maze. Recipients injected with RNA from donors trained to arm A chose A in 15 out of 21 cases, while those receiving RNA from B-trained donors chose B in 14 out of 21 cases, a significant deviation from chance (p < 0.02 via chi-square test).^[11] James V. McConnell extended similar approaches to planarian flatworms in the mid-1960s, building on his earlier cannibalism studies. In a 1965 investigation, McConnell prepared extracts from planarians conditioned to exhibit avoidance behavior (body contraction) in response to light paired with electric shock, then injected these RNA-containing fractions into untrained worms. The recipients displayed accelerated acquisition of the light-shock association, with reports indicating shortened training times compared to controls not receiving extracts. This work suggested that chemical molecules, particularly RNA, could mediate the transfer of specific learned responses across individuals.^[1] These experiments sparked widespread interest, leading to replications across multiple labs and species, with some studies reporting enhanced performance in recipients relative to untreated controls. For instance, in related RNA injection studies, experimental groups achieved mean response rates approximately 50% higher than controls (0.394 versus 0.263 correct responses per trial). However, a key controversy erupted in 1966 at the Psychonomic Society meeting, where McConnell's claims faced intense scrutiny over methodological artifacts like sensitization or non-specific arousal, contributing to replication failures and subsequent cuts to his research funding.^[1]^[12]

Proposed mechanisms

Memory RNA hypothesis

The memory RNA hypothesis posits that ribonucleic acid (RNA) functions as a chemical carrier of memory traces, synthesized in the brain during learning and capable of being extracted from trained organisms and transferred to untrained ones to confer learned behaviors. Proposed by James V. McConnell in 1962 based on experiments with planarian flatworms, the idea suggested that these "memory molecules" encode specific engrams—the physical representations of memories—allowing for direct molecular transfer of information between individuals.^[1] Under this hypothesis, learning induces changes in RNA molecules, such as increases in RNA content, alterations in base composition ratios, or three-dimensional conformations, which stabilize the engram and enable its persistence beyond the initial training period. These modified RNA structures were thought to direct behavioral responses upon transfer, as demonstrated in early tests where RNA extracts from trained donors accelerated learning in recipients. Unlike proposed protein-based storage mechanisms, RNA's solubility and extractability facilitated experimental transfer, emphasizing its role as a mobile agent for propagating memory traces across organisms.^[13] Supporting evidence from the 1960s included McConnell's planarian studies, where untrained flatworms injected with RNA from light-shock-conditioned donors exhibited reduced trials needed for conditioning compared to controls, with ribonuclease treatment abolishing the effect to confirm RNA's involvement. Additional era research, such as independent replications in rats and other species, bolstered the claim by showing similar transfer effects with brain RNA extracts, though later scrutiny questioned methodological artifacts. The hypothesis highlighted RNA's potential over DNA or proteins due to its rapid synthesis during learning and resistance to certain disruptions, like those tested in regeneration experiments where memory persisted in reforming tissues.^[1]^[14]

Role of synaptic plasticity and engrams

The engram, originally conceptualized by Karl Lashley as the physical trace of memory in the brain, refers to the lasting structural or biochemical changes that encode specific experiences.^[15] In contemporary neuroscience, engrams are understood as sparse ensembles of neurons that are activated during learning and whose reactivation is sufficient for memory retrieval, distributed across brain regions such as the hippocampus and cortex.^[16] These neuronal populations form the substrate for memory storage, with their stability relying on mechanisms like synaptic strengthening and connectivity changes. In the context of memory transfer, hypotheses propose that exogenous molecules, such as RNA extracted from trained organisms, can modulate engram formation by influencing synaptic plasticity in recipient brains. Specifically, transferred RNA is thought to modulate gene expression through epigenetic mechanisms, influencing synaptic plasticity and long-term potentiation (LTP)—a cellular correlate of learning wherein synaptic efficacy increases persistently.^[17] This modulation may occur through epigenetic mechanisms, such as DNA methylation, that enhance neuronal excitability and facilitate sensorimotor synapse strengthening, thereby imprinting engram-like traces without direct experience.^[2] Recent models emphasize non-coding RNAs, such as microRNAs, in mediating these epigenetic effects on synaptic plasticity. Early claims from the memory RNA hypothesis, suggesting RNA as a direct carrier of learned information, laid groundwork for these ideas by implying molecular mediation of neural changes.^[18] Models from the 1970s, building on experiments showing RNA synthesis inhibitors disrupt long-term memory, posited that injected RNA from trained animals triggers cascades of gene expression in recipients, leading to protein synthesis that sustains synaptic plasticity and engram consolidation. For instance, work by researchers like Holger Hydén demonstrated learning-induced RNA alterations in neurons, hypothesized to direct the production of plasticity-related proteins, a process transferable via RNA extracts to induce analogous changes in naive subjects. This view contrasts with classical engram theories, which emphasized fixed, hardwired neural patterns shaped solely by activity-dependent rewiring, by introducing dynamic, chemically inducible modifications that allow external molecules to reshape engrams post-formation.

Key experiments

Planarian flatworm studies

Planarian flatworm studies on memory transfer utilized the regenerative capabilities of Dugesia dorotocephala to investigate whether learned behaviors could persist through brain reconstruction and be conveyed to naive organisms. Researchers trained planarians via classical conditioning, repeatedly pairing a neutral light stimulus with an aversive electric shock to condition an avoidance response, such as body contraction or turning away from the light. Following training, the worms were decapitated or sectioned into pieces and placed in conditions allowing regeneration, which typically takes 10–14 days to form a new head and brain. Regenerated worms were then re-exposed to the light stimulus alone and assessed for the presence of the conditioned avoidance response. This methodology allowed testing whether memory was encoded in structures beyond the original central nervous system, such as diffusible molecules throughout the body.^[9] A landmark experiment by McConnell, Jacobson, and Kimble demonstrated that regenerated planarians from trained donors retained the conditioned avoidance behavior at levels comparable to uncut trained controls, whereas regenerated controls from untrained donors showed no such response. This suggested that the memory trace was not destroyed by the loss of the original brain but could be re-expressed during regeneration, possibly through molecular signals distributed across the body. These findings challenged the view that memory depends exclusively on fixed neural circuits and implied a chemical basis for storage that survives cellular turnover.^[9] Building on retention during regeneration, 1960s experiments explored direct transfer of memory. Trained planarians were homogenized in a buffer solution to prepare tissue extracts, which were centrifuged and purified to isolate ribonucleic acid (RNA) fractions presumed to carry the engram. These extracts were injected into the body cavity of untrained recipient planarians, which were subsequently trained and tested on the light-shock avoidance task. Jacobson, Fried, and Horowitz reported that recipients injected with RNA from trained donors learned the task significantly faster—requiring fewer trials to reach criterion performance—than those receiving RNA from untrained donors or vehicle injections alone. This provided evidence for intercellular transfer of learned information via RNA, aligning with contemporary ideas of molecular memory encoding.^[19] To delineate the molecular basis, researchers employed puromycin, an antibiotic that inhibits protein synthesis without affecting RNA function. Planarians were trained, treated with puromycin to block new protein production during regeneration or prior to transfer, and then tested. Retention of the avoidance response persisted despite protein synthesis blockade, indicating that ongoing protein formation was not required for memory maintenance or transfer, thereby isolating RNA as the likely carrier of the behavioral engram. McConnell's cannibalism variant further corroborated this, where naive planarians ingesting homogenized trained donors exhibited accelerated avoidance learning compared to those ingesting untrained material. These results collectively positioned planarians as a key model for chemical theories of memory in the mid-20th century.^[1]

Aplysia snail research

In the 21st century, research on memory transfer in the marine snail Aplysia californica revived interest in the concept, building on earlier invertebrate studies by demonstrating RNA-mediated transfer of sensitization memory.^[20] A seminal 2018 study led by David Glanzman at UCLA involved sensitizing donor snails through two rounds of tail-nerve shocks administered 24 hours apart, with each round consisting of five bouts at 20-minute intervals; each bout delivered three electrical trains (1-second duration, 40 Hz, 120 V).^[20] RNA was then extracted from the pleural-pedal and abdominal ganglia of these trained donors 48 hours after the final shock, using TRIzol reagent, and 70 micrograms of the RNA was injected intrahemocoelically into the neck region of naive, untrained recipient snails.^[20] The recipient snails exhibited a markedly enhanced siphon-withdrawal reflex (SWR) in response to tactile stimulation, with reflex duration averaging 38.0 ± 4.6 seconds—approximately sevenfold longer than the 5.4 ± 3.9 seconds observed in controls (p < 0.003, n=7 per group)—indicating successful transfer of long-term sensitization memory.^[20] This behavioral effect persisted for at least 24 hours post-injection, mimicking the duration of sensitization in directly trained snails.^[20] In parallel in vitro experiments, application of the trained RNA to isolated sensory neurons increased their excitability by 56.66 ± 22.07% (n=19), without affecting motor neurons, suggesting a specific enhancement of sensory-motor synaptic strength underlying the transferred memory.^[20] Control injections using RNA from untrained snails produced no significant SWR enhancement (5.4 ± 3.9 seconds, n=7), confirming the specificity of the effect to training-related RNA components.^[20] Further analysis revealed that the transfer required epigenetic modifications, as blocking DNA methylation with RG108 abolished the effect, while inhibiting it after injection prevented behavioral expression.^[20] A key innovation in the study was the use of RNA sequencing to profile differentially expressed transcripts in trained versus untrained ganglia, identifying non-coding RNAs such as microRNAs and piRNAs as potential carriers of the memory engram, thereby challenging synapse-centric models of memory storage.^[20]

Mammalian transfer attempts

Attempts to transfer memory in mammals, particularly rats and mice, began in the 1960s following initial successes in invertebrates, but yielded mixed results marked by partial accelerations in learning alongside widespread replication failures. In rat studies during the 1960s and 1970s, researchers injected brain extracts from trained donors into naive recipients to assess transfer in avoidance tasks, such as passive avoidance where rats learn to avoid a shock-associated compartment. For instance, experiments reported that recipients of extracts from trained rats exhibited 20-30% faster acquisition of the avoidance response compared to those receiving extracts from untrained controls, suggesting a potential chemical basis for memory facilitation.^[21]^[22] Byrne et al. (1967) conducted intracisternal injections of brain extracts in rats, observing behavioral modifications indicative of learning acceleration in Y-maze discrimination tasks, with treated animals showing reduced errors by approximately 25% relative to controls.^[23] Similar findings emerged in other labs using intraperitoneal or intraventricular administration of RNA-containing extracts, where recipient rats demonstrated enhanced performance in shuttle-box active avoidance, completing training trials 20-30% quicker than sham-injected groups. However, these effects were task-specific and modest, often requiring multiple injections for detection.^[24] A key challenge arose from controls using RNase treatment to degrade RNA in extracts; 1970s reviews, including those synthesizing Ungar's work, found that transfer effects often persisted or diminished non-specifically after enzymatic digestion, questioning RNA's direct role and suggesting artifacts like residual peptides or procedural biases.^[25] Overall, few mammalian studies reported reliable, replicable effects, frequently explained by confounding factors such as stress pheromones released by trained donors influencing recipient arousal rather than true memory transfer.^[1] This skepticism contrasted with more consistent invertebrate results, ultimately diminishing research momentum by the late 1970s.^[26]

Criticisms and controversies

Methodological challenges

Early memory transfer experiments faced significant methodological hurdles that cast doubt on their validity, primarily due to inadequate controls and potential artifacts in behavioral assays. One major concern was contamination risks in brain extracts used for injection, where non-specific substances such as peptides or hormones could induce physiological changes mimicking learned behaviors rather than transferring true memories. For instance, in rat studies attempting to isolate "scotophobin" as a memory molecule, impurities in extract preparations were suspected to account for observed effects, leading to widespread skepticism about the specificity of the transfers.^[27] Statistical issues further undermined these claims, with many 1960s studies employing small sample sizes (often n < 20) and lacking blinding procedures, which facilitated experimenter bias and p-hacking. Replication attempts, such as those by Halas et al. (1962), highlighted problems with null-hypothesis significance testing in underpowered designs, where non-significant results were dismissed despite suggestive trends in conditioning rates.^[10] A pivotal event came in the late 1960s and 1970s, when multiple independent replications failed to demonstrate transfer after implementing stricter controls for sensory cues and other confounds. Notably, Byrne et al. (1966) coordinated efforts across eight laboratories and 23 researchers, reporting no evidence of memory transfer in rats using brain extracts, attributing prior positive findings to uncontrolled variables like stress or non-specific arousal.^[28]^[29] RNase enzyme tests intended to validate the memory RNA hypothesis yielded inconsistent results, pointing to non-specific degradation effects rather than targeted disruption of memory molecules. In Corning and John's (1961) experiment with regenerated planarians, RNase treatment abolished retention in tail fragments but spared it in heads, suggesting the enzyme's impact was tied to regeneration dynamics or toxicity rather than RNA-specific memory erasure.^[30] These challenges often intertwined with alternative behavioral explanations, such as sensitization from extract-induced stress, though methodological flaws alone sufficed to discredit many claims.^[10]

Alternative interpretations

One prominent alternative interpretation of apparent memory transfer effects in early experiments involves the hypothesis of olfactory cues, such as pheromones or stress odors released by trained animals during preparation of tissue extracts, prompting avoidance behaviors in recipient animals rather than conveying specific memory traces.^[25] This explanation posits that the observed responses were due to chemosensory detection of alarm pheromones or stress-related volatiles, mimicking learned avoidance without true transfer of associative information. A related sensitization model offers another non-transfer account, particularly in invertebrate studies. Critics of the 2018 RNA injection experiments with Aplysia snails have suggested that the transferred material might induce a general state of heightened arousal or non-specific sensitization, enhancing responsiveness to stimuli broadly rather than implanting discrete memories.^[2] Sensitization, as a form of non-associative learning, increases defensive reactions following noxious exposure but lacks the stimulus-specific pairing characteristic of associative memory.^[31] Central to these interpretations is the distinction between associative and non-associative transfer. Associative transfer would require evidence of specific, stimulus-linked memories (e.g., conditioned light avoidance in planarians), whereas non-associative effects, such as habituation or sensitization, involve generalized changes in arousal or responsiveness without targeted associations.^[32] This differentiation highlights how apparent transfer might reflect artifactual sensitization rather than encoded engrams.^[13] Supporting cue-based artifacts, replication attempts in the 1970s and 1980s using improved extract preparations failed to produce transfer effects, suggesting that uncontrolled olfactory contaminants in earlier crude preparations accounted for prior positive results.^[33]^[23] These findings align with broader methodological challenges in extract preparation, where incomplete removal of sensory cues could confound interpretations.^[23] Recent criticisms of RNA-based memory transfer, such as the 2018 Aplysia study, emphasize limited replicability in vertebrates and questions about epigenetic mechanisms' role in complex declarative memories, with ongoing debates as of 2023 regarding applicability beyond simple sensitization.^[34]

Modern developments and implications

Recent RNA-based findings

In the 2010s, research in David Glanzman's laboratory at UCLA advanced the understanding of RNA's role in memory transfer through experiments on the marine mollusk Aplysia californica. Beginning with studies on microRNA regulation of synaptic plasticity around 2013, the lab demonstrated that specific microRNAs, such as miR-22 and miR-124, modulate long-term heterosynaptic facilitation by targeting mRNAs involved in protein synthesis at synapses.^[35] This work culminated in a 2018 study showing that RNA extracted from the central nervous systems of Aplysia trained for long-term sensitization (LTS)—a non-associative form of memory—could be injected into untrained animals, inducing LTS-like behavioral responses, such as enhanced siphon-withdrawal reflexes.^[2] At the cellular level, this transferred RNA increased the excitability of sensory neurons in recipients, evidenced by elevated spike-firing rates in response to depolarizing currents, without altering synaptic connectivity.^[2] The effect persisted for over 24 hours and was blocked by inhibitors of DNA methylation, indicating that the RNA acts through epigenetic modifications to establish a persistent engram.^[2] Building on these invertebrate findings, extensions in the 2020s have explored RNA transfer mechanisms in mammalian models, particularly in the mouse hippocampus, where spatial memory formation relies on engram ensembles. A key discovery involves the activity-regulated cytoskeleton-associated (Arc) gene, whose protein product forms virus-like capsids that encapsulate and transfer RNA intercellularly between neurons via extracellular vesicles. This mechanism, first detailed in 2018, enables the dissemination of plasticity-related transcripts, such as those encoding synaptic proteins, across neuronal networks to consolidate engrams. However, direct evidence for memory transfer via Arc-mediated RNA in mammals remains limited and debated, with no confirmed replications of behavioral transfer akin to the Aplysia studies as of 2025. This body of work signifies a conceptual shift toward epigenetic mechanisms in memory storage, where RNAs—particularly microRNAs and long non-coding RNAs—do not merely encode information but actively influence DNA methylation patterns to sustain long-term engrams. In Aplysia, injected RNAs upregulated methyltransferases, leading to hypermethylation of promoter regions that repress forgetting-related genes, thereby locking in sensitization traces.^[2] These findings underscore RNA's dual role as both a carrier of memory signals and a regulator of chromatin states, bridging short-term plasticity with enduring storage, though applicability to declarative memories in vertebrates continues to be explored.^[36] Recent 2025 studies on RNA splicing in Alzheimer's models suggest potential links to memory restoration, but without direct transfer.^[37]

Ethical and future applications

The therapeutic potential of memory transfer lies in its possible application to psychiatric and neurodegenerative disorders, such as post-traumatic stress disorder (PTSD) and Alzheimer's disease, where transferring or modulating memories could alleviate symptoms by introducing positive associative experiences or restoring cognitive functions through RNA-based interventions.^[38] For PTSD, research indicates that microRNAs influencing transcriptional changes in fear memory modulation hold promise for targeted therapies that could hypothetically extend to transferring adaptive memory elements to reduce trauma persistence.^[39] In Alzheimer's disease, emerging RNA therapeutics, including small interfering RNAs (siRNAs) and antisense oligonucleotides, aim to address synaptic loss and amyloid pathology, potentially paving the way for hypothetical RNA-mediated memory enhancement or transfer to counteract memory deficits, though direct transfer remains exploratory.^[40] Recent findings on arcRNAs, such as those derived from the Arc gene that facilitate intercellular RNA transfer between neurons, underscore the biological feasibility of such mechanisms for therapeutic development.^[41] Neuroethics discussions in 2023 emphasized significant concerns regarding consent and identity alteration in potential human applications of memory transfer technologies, arguing that such interventions could disrupt personal narrative coherence and autonomy through unintended side effects on memory integrity.^[42] These debates highlight the risk of ethical harms, including the erosion of self-identity if memories are selectively modified or transferred without fully informed consent, particularly in vulnerable populations.^[43] Broader neuroethics frameworks stress the need for robust safeguards to prevent non-therapeutic uses that might commodify or manipulate individual histories.^[44] Looking ahead, memory transfer could integrate with brain-computer interfaces (BCIs) to enable digital memory uploads, allowing for external storage, enhancement, and potentially shared access to experiences, which might revolutionize cognitive augmentation and data preservation.^[45] Such advancements raise prospects for non-invasive BCIs to facilitate memory encoding and retrieval in real-time, though they also amplify ethical risks around privacy and equity in access.^[46] As of 2025, no human clinical trials for memory transfer have been initiated, with research confined to preclinical models.^[47] Animal welfare issues in foundational studies involving snails and rats, such as those probing memory mechanisms, have drawn attention from organizations like the ASPCA, which advocate for minimized suffering and ethical oversight in neuroscience experiments using invertebrates and rodents.^[48]

References

[1]
The memory-transfer episode - American Psychological Association
Jun 1, 2010 · Everything changed when, in late 1965, four independent labs reported successful memory-transfer experiments using rats (and in one case, cross- ...
[2]
RNA from Trained Aplysia Can Induce an Epigenetic Engram for ...
May 14, 2018 · It is demonstrated that the memory for long-term sensitization (LTS) in the marine mollusk Aplysia can be successfully transferred by injecting RNA from ...
[3]
Georges Ungar and memory transfer - PubMed
The idea that memories could be transferred from one organism to another by administration of a "trained" donor brain to a naive recipient seized both ...
[4]
[PDF] Richard Semon's Theory of Memory - Rotman Research Institute
In the first decade of the 20th century, Richard Semon put forward a theory of memory that anticipated numerous recent developments in memory research.Missing: chemical | Show results with:chemical
[5]
Engrams and biological regulation: What was “wrong” with organic ...
Mar 13, 2015 · When embryos took form, stimuli specific to stored ancestral traces were re-activated in changing engram complexes—as hereditary organic memory.
[6]
[PDF] KARL SPENCER LASHLEY - Biographical Memoirs
KARL SPENCER LASHLEY, one of the great psychologists of our time, was born on June 7, 1890, and died on August 7, 1958. His birth occurred in Davis, ...<|separator|>
[7]
Fifty Years Since Lashley's In Search of the Engram: Refutations and ...
Aug 7, 2025 · One of the most intensive searches to localize memory traces-or engrams-within the brain was initiated by Karl Spencer Lashley in the 1920's ( ...Missing: 1940s | Show results with:1940s
[8]
Behavioral Research with Planaria - PMC - PubMed Central - NIH
Nov 9, 2018 · In the 1950s and 1960s, McConnell's planarian laboratory posited that conditioned behavior could transfer after regeneration, and through ...
[9]
https://pubmed.ncbi.nlm.nih.gov/13641455/
[10]
Maze preferences in naive rats produced by injection of ribonucleic ...
Maze preferences in naive rats produced by injection of ribonucleic acid from trained rats! ALLAN L. JACOBSON, FRANK R. BABICH, SUZANNE BUBASH2 ANO CAROLYN ...Missing: 1960s | Show results with:1960s
[11]
The transfer of learned behavior from trained to untrained rats by ...
with dosages of 1.4 brains per rat (eight experimental and eight control rats) has a mean response rate of 0.394 for the experimental group, and 0.263 for the ...
[12]
The stability of memories during brain remodeling: A perspective
In this Perspective, we discuss relevant data in regenerating planaria, metamorphosing insects, and hibernating ground squirrels.
[13]
Memory transfer in planarians: An artifact of the experimental variables
McConnell (1962) interpreted the data as indicating that memory transfer by cannibalism had been demonstrated and it was tentatively hypothesized that the ...
[14]
The Emergent Engram: A Historical Legacy and Contemporary ...
Karl Lashley used various post-training lesion techniques to disrupt the retrieval of memory in rats and monkeys (Lashley, 1950). After decades of systematic ...Missing: 1920s- 1940s
[15]
Engram neurons: Encoding, consolidation, retrieval, and forgetting ...
Jun 28, 2023 · Third, we describe how these changes during encoding and consolidation guide neural reactivation during retrieval, and facilitate memory recall.
[16]
Is plasticity of synapses the mechanism of long-term memory storage?
Jul 2, 2019 · In this review, we address the key findings from the synaptic plasticity literature that make these phenomena such attractive memory mechanisms.
[17]
https://www.nature.com/articles/s41539-019-0048-y
[18]
The effects of regeneration upon retention of a conditioned response ...
The effects of regeneration upon retention of a conditioned response in the planarian. J Comp Physiol Psychol. 1959 Feb;52(1):1-5. doi: 10.1037/h0048028.Missing: memory | Show results with:memory
[19]
I. Transfer of Learning by Injection of Ribonucleic Acid | Nature
Planarians and Memory: I. Transfer of Learning by Injection of Ribonucleic ... McConnell, J. V., J. Neuropsychiat., 3 (suppl. 1), 542 (1962). Google ...Missing: study | Show results with:study
[20]
https://doi.org/10.1523/ENEURO.0038-18.2018
[21]
learned behavior by brain extracts, ih - PNAS
the possibility of "memory transfer" by means of brain extracts, but reveals a hitherto unsuspected degree of complexity in the kinds of phenomena which may.Missing: 1960s | Show results with:1960s<|separator|>
[22]
Memory Transfer - PubMed
W L Byrne, D Samuel, E L Bennett, M R Rosenzweig, E Wasserman. PMID: 5939939; DOI: 10.1126/science.153.3736.658. MeSH terms. Animals; Behavior, Animal; Brain* ...Missing: et 1967
[23]
(PDF) RNA and memory transfer - ResearchGate
May 27, 2015 · "Learned behavior has been reported to be transferred as a result of injecting RNA-containing fractions from the brains of trained rats ...
[24]
Analysis of Memory Transfer and Enhancement - jstor
BYRNE, W. L., and A. HUGHES. 1967. "Behavioral. Modification by Injection of Brain Extract from. Trained Donors." Federation Proc. 26: p. 676.
[25]
(PDF) Georges Ungar and memory transfer. - ResearchGate
Sep 23, 2009 · This paper reviews Ungar's work on memory transfer (and in particular on the scotophobin molecule), with an analysis of its successes and failures.
[26]
Claim of memory transfer made 50 years ago - Science News
Experiments with rats, showing how chemicals from one rat brain influence the memory of an untrained animal, ...
[27]
50 years ago, scientists were on the trail of 'memory molecules'
Nov 5, 2021 · The idea that scotophobin stores memories and can be used to transfer them between organisms was met with intense skepticism and was ...Missing: criticism contamination
[28]
Memory Transfer - Science
GROSS, C.G., TRANSFER OF LEARNED RESPONSE BY RNA INJECTION - FAILURE OF ATTEMPTS TO REPLICATE, SCIENCE 150: 1749 (1965). ... Byrne et al. ,. Memory Transfer.
[29]
[PDF] What history tells us VI. The transfer of behaviours by macromolecules
At the end of the 1970s, similar transfer experiments in Robert Weinberg's hands played a major role in the first identification of oncogenes. (Shih et al 1979; ...
[30]
Effect of Ribonuclease on Retention of Conditioned Response in ...
Effect of Ribonuclease on Retention of Conditioned Response in Regenerated Planarians. W. C. Corning and E. R. JohnAuthors Info & Affiliations. Science. 27 Oct ...
[31]
RNA from Trained Aplysia Can Induce an Epigenetic Engram for ...
May 21, 2018 · It is demonstrated that the memory for long-term sensitization (LTS) in the marine mollusk Aplysia can be successfully transferred by injecting RNA from ...
[32]
Memory transfer vs. sensitization in cannibal planarians
Aug 7, 2025 · Memory transfer in planarians: An artifact of the experimental variables. September 1966 · Psychonomic Science. D. R. Walker. The conditioning ...Missing: Society | Show results with:Society
[33]
[PDF] The molecular memory code and synaptic plasticity: A synthesis
Jan 4, 2023 · In particular, McConnell speculated that memories were stored inside neoblasts—undifferentiated, pluripotent cells that circulate throughout the ...
[34]
MicroRNA-22 Gates Long-Term Heterosynaptic Plasticity in Aplysia ...
Jun 30, 2015 · We describe a sensory neuron-specific microRNA 22 (miR-22) that has multiple binding sites on the mRNA of CPEB and inhibits it in the basal state.
[35]
DNA Methylation in Long-Term Memory | Physiology
In regard to the formation upon learning, it is certain that changes of DNA methylation could be triggered after neuronal activity due to its functioning ...
[36]
Epigenetic mechanisms in learning and memory
Nov 8, 2012 · Recent discoveries have associated epigenetic mechanisms, including DNA methylation, histone modifications, and microRNA (miRNA) processing, ...
[37]
Can RNA Affect Memory Modulation? Implications for PTSD ...
The current state of research suggests that transcriptional changes play a major role in memory modulation and targeting them through microRNAs may hold promise ...Missing: Alzheimer's | Show results with:Alzheimer's
[38]
RNA's Pivotal Role in Fear Memory and PTSD Treatment
Nov 30, 2023 · Another study identified m6A-modified RNAs that regulate synaptic plasticity, crucial for fear extinction memory, a key factor in PTSD. These ...
[39]
New RNA-Based Breakthroughs in Alzheimer's Disease Diagnosis ...
This review aims not only to describe the disease and its impact but also to collect the currently available diagnostic and therapeutic strategies.
[40]
[PDF] Intercellular Communication in the Nervous System Goes Viral
The neuronal gene Arc forms virus-like capsids that transfer RNA between neurons via specialized extracellular vesicles, a new intercellular communication ...Missing: 2020-2025 | Show results with:2020-2025<|control11|><|separator|>
[41]
Neuromodulation and memory: exploring ethical ramifications in ...
Dec 20, 2023 · The study contends that undesired side effects resulting from memory modulation can lead to significant identity harms, disrupting the coherence ...Missing: transfer | Show results with:transfer
[42]
Personal autonomy in memory modification technology: a critical ...
Sep 16, 2024 · Zawadzki (2022) argues that MMT could alter a person's social life and hurt the “autonomous construction” of personal identity. Similarly, ...
[43]
Neuroethics and neurorights applied in neural manipulation in ...
Memory modification techniques make it possible to completely erase a memory or induce amnesia, thereby reconstructing personal identity, which can be ...
[44]
Brain-computer interfaces for memory enhancement: Scientometric ...
Brain-computer interfaces have the potential to transform society by enhancing brain function. These electronic devices could enable the rapid acquisition ...
[45]
Brain–computer interface: trend, challenges, and threats - PMC
Aug 4, 2023 · Brain–computer interface (BCI), an emerging technology that facilitates communication between brain and computer, has attracted a great deal of research in ...
[46]
What to expect from Neuralink in 2025 - MIT Technology Review
Jan 16, 2025 · Considering these two studies only, Neuralink would carry out at least two more implants by the end of 2025 and eight by the end of 2026.
[47]
[PDF] AVMA Guidelines for the Euthanasia of Animals: 2020 Edition*
The panel is required to do a comprehensive review and update of the report at least every 10 years, although more frequent major revisions are possible based ...Missing: ASPCA | Show results with:ASPCA