Of Mice and Memory

For the past decade, in experiments with mice, rats and even lowly flatworms, a number of researchers have claimed success in transferring learning or memory between organisms, usually by feeding or injecting one animal with the brain extract from another. Those claims have never been completely accepted, however, because other scientists were not always able to duplicate the experiments, and no one could identify the exact nature of the so-called "memory molecules" necessary for such a transfer. The skeptics may have to reconsider their stand. Last week a Baylor University scientist reported that he had identified and synthesized a chemical that produces a specific memory in rats and mice: fear of the dark.

Shunning the Dark. The announcement was made by Hungarian-born Neurochemist Georges Ungar, 64, who has spent years experimenting with memory transfer. In his most notable experiment (TIME, April 19, 1968), he jolted rats and mice with an electrical shock whenever they strayed into a blacked-out box, eventually conditioning them to fear the dark. Then, after decapitating his fear-trained animals, he injected a broth made out of their brain tissue into the abdominal cavities of normal mice, which ordinarily prefer the dark. More often than not, he found, the injected rodents--contrary to their nature--also began to shun the dark.

When he started his work, Ungar had only the vaguest suspicions about the chemistry involved in this transfer of fear. But after repeated experimentation, he concluded that the message was coded in amino acid chains called peptides, which are small proteins. Finally, he narrowed the search to a single peptide--consisting of a sequence of 15 amino acids--that he named scotophobin, from the Greek words for dark and fear. To check his conclusion, Ungar asked Wolfgang Parr, a University of Houston chemist, to duplicate scotophobin using only off-the-shelf chemicals. The synthetic variety differed slightly from the natural chemical produced in the brains of fear-induced rats, says Ungar, but it was still sufficiently potent to make nighttime cowards of most normal rats and mice.

Ungar and other researchers strongly suspect that the chemical mechanism for such learning is governed by RNA molecules in the brain cells. By directing the assembly of the body's 20 or so amino acids into the proper combinations, these master molecules are apparently able to make an imprint of a memory or learning experience. Ungar is convinced that chemical processes similar to those in the brains of his rats also occur in the brains of higher animals, including man. If this is indeed true, it may eventually be possible to enhance man's knowledge and to treat at least some forms of senility and mental retardation by simple injections of the chemicals of memory.

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