Turnover of Cerebral DNA in Learning and Sleep

Abstract

The possible involvement of brain DNA in learning received consideration some time ago, when nucleic acids appeared to be suitable candidates for the role of information storage molecules (Hyden, 1959; Gaito, 1961). DNA however was quickly put aside in view of its role as depository of genetic information and because of its presumed metabolic stability (Briggs and Kitto, 1962). On these counts RNA remained as a better candidate, at least until it was shown that brain had the same major RNA components of other organs (Vesco and Giuditta, 1967), thus leaving little room for brain specific RNA memory molecules. More convincing hypotheses were then advanced and RNA acquired a new role in learning as intermediate in the process of protein synthesis (Briggs and Kitto, 1962). It is ironical (and relevant) to note that both conclusions were based on incorrect assumptions. Indeed, a large population of brain-specific RNA transcripts came to be discovered in the early seventies following the application of hybridization techniques (Hahn and Laird, 1971; Brown and Church, 1971; Grouse et al., 1972). Their role in brain activity remains still to be clarified (Chaudari and Hahn, 1983; Kaplan, 1983). As to DNA, our views on its functional capacities have now become substantially more flexible in order to accomodate newly discovered features such as amplification, transposition, magnification and genomic rearrangement (Lewin, 1983).