Memory transfer was a biological process proposed by

James V. McConnell James V. McConnell (October 26, 1925 – April 9, 1990) was an American biologist and animal psychologist. He is most known for his research on learning and memory transfer in planarians conducted in the 1950s and 1960s. McConnell also publish ...

and others in the 1960s. Memory transfer proposes a chemical basis for

memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, ...

termed memory

RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...

which can be passed down through flesh instead of an intact nervous system. Since RNA encodes information living cells produce and modify RNA in reaction to external events, it might also be used in

neuron A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. N ...

s to record stimuli. This explained the results of McConnell's experiments in which

planarian A planarian is one of the many flatworms of the traditional class Turbellaria. It usually describes free-living flatworms of the order Tricladida (triclads), although this common name is also used for a wide number of free-living platyhelmint ...

s retained memory of acquired information after

regeneration Regeneration may refer to: Science and technology * Regeneration (biology), the ability to recreate lost or damaged cells, tissues, organs and limbs * Regeneration (ecology), the ability of ecosystems to regenerate biomass, using photosynthesis ...

. Memory transfer through memory RNA is not currently a well-accepted explanation and McConnell's experiments proved to be largely

irreproducible Reproducibility, also known as replicability and repeatability, is a major principle underpinning the scientific method. For the findings of a study to be reproducible means that results obtained by an experiment or an observational study or in a ...

. In McConnell's experiments, he classically conditioned planarians to contract their bodies upon exposure to light by pairing it with an electric shock. The planarians retained this acquired information after being sliced and regenerated, even after multiple slicings to produce a planarian where none of the original trained planarian was present. The same held true after the planarians were ground up and fed untrained

cannibalistic Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species In biology, a species is the basic ...

planarians, usually

Dugesia dorotocephala ''Girardia dorotocephala'' is a species of dugesiid triclad native to North America. It has been accidentally introduced in Japan.Sluys, R., Kawakatsu, M., Yamamoto, K. (2010). "Exotic freshwater planarians currently known from Japan". ''Belgian ...

. As the nervous system was fragmented but the nucleic acids were not, this seemed to indicate the existence of memory RNA but it was later suggested that only sensitization was transferred, or that no transfer occurred and the effect was due to

stress hormones Stress hormones are secreted by endocrine glands to modify one's internal environment during times of stress. By performing various functions such as mobilizing energy sources, increasing heart rate, and downregulating metabolic processes which a ...

in the donor or

pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...

trails left on dirty lab glass. However, other experiments seem to support the original findings in that some memories may be stored outside the brain.

References

{{Biochem-stub RNA Molecular neuroscience