Memory transfer

Memory transfer was a biological process proposed by James V. McConnell and others in the 1960s. Memory transfer proposes a chemical basis for memory termed memory RNA which can be passed down through flesh instead of an intact nervous system. Since RNA encodes information^[1] living cells produce and modify RNA in reaction to external events, it might also be used in neurons to record stimuli.^[2][3][4] This explained the results of McConnell's experiments in which planarians retained memory of acquired information after regeneration. Memory transfer through memory RNA is not currently a well-accepted explanation and McConnell's experiments proved to be largely irreproducible.^[5]

In McConnell's experiments, he classically conditioned planarians to contract their bodies upon exposure to light by pairing it with an electric shock.^[6][5] 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.^[5] The same held true after the planarians were ground up and fed untrained cannibalistic planarians, usually Dugesia dorotocephala.^[5][7] As the nervous system was fragmented but the nucleic acids were not, this seemed to indicate the existence of memory RNA^[5] but it was later suggested that only sensitization was transferred,^[6] or that no transfer occurred and the effect was due to stress hormones in the donor or pheromone trails left on dirty lab glass.^[2] However, other experiments seem to support the original findings in that some memories may be stored outside the brain.^[1][8][9]