A study of sea slugs presents a rival theory to the commonly held belief of most neuroscientists: that long term memories are encoded within strengthened connections between nerve cells in the brain. When poked, the slugs pull their water-filtering siphon back into their bodies. In this study, scientists used electric shocks to instill a longer period of response time to the reflexive reaction of sea slugs. The researchers then proceeded to extract RNA from the conditioned slugs and inject it into untreated slugs. Shockingly, the slugs with the injected RNA proceeded to display the same longer periods of response to stimulus as the slugs that had originally been conditioned to do so.
So what is RNA? RNA, or ribonucleic acid, is a molecule composed of nucleotides; the nucleotides themselves are made up of a nitrogenous base, a ribose sugar, and a phosphate. RNA is similar to DNA but contains a different kind of structural sugar and does not form the famous double-helix shape. RNA performs a variety of essential functions in the cell, and is vital to the process of protein synthesis – it is capable of transcribing the genetic information encoded in DNA, “reading” that code, and selecting the corresponding amino acids to build the protein encoded by the original DNA. RNA is involved in many other processes, but the full extent of its role in the cell has yet to be completely understood. It is this more mysterious RNA that David Glanzman, a coauthor of the study, believes the possible memory storage lies.
(Bedecarrats, Chen, Pearce, Cai, & Glanzman, RNA from Trained Aplysia Can Induce an Epigenetic Engram for Long-Term Sensitization in Untrained Aplysia, 14 May 2018, eNeuro)