Farouq Hassanali

THE CHEMICAL TRANSFER OF MEMORY

In the 1950s, a scientist named James McConnell trained planarian worms to scrunch up their bodies in response to light – he did this by shining a bright light on the worms as they swam along the bottom of a trough and giving them a mild shock which caused their bodies to arch or ‘scrunch’. The worms eventually learned to associate light with shock and began to scrunch upon exposure to light (whether or not the shock was delivered). Training the worms required great skill – skill that McConnell built up slowly over several years. McConnell tried feeding minced portions of trained worms to some untrained worms and found that these untrained worms were 1.5 times more likely to scrunch in response to light than the untrained worms that were not fed in the same manner. McConnell believed that memories (of scrunching upon exposure to light) were stored in chemicals and had been transferred between the worms. However, his results could not be replicated in other labs. McConnell claimed that training the worms was a matter of skilled practice (something that he had to develop over several years) and that the other scientists’ poor results were the outcomes of poor training technique and a failure to understand the worms. In 1965, public attention turned to another scientist named Georges Ungar, who believed he had shown that memories could be chemically transferred in mammals too.

Ungar exposed rats to the sound of a loud bell until they became accustomed to it and ceased to exhibit the usual ‘startle reaction’. He ground up the brains of these rats and injected the brain extract into mice – the transfer of the habituation trait between these two different mammals was apparently a success. Some scientists were able to replicate the results while others were not – the former accused the latter of being incompetent in performing experiments; the latter accused the former of being frauds and falsifying the results. In 1967, Ungar performed an experiment in which rats had to choose between entering a lighted or a darkened box (a rat’s natural preference would be for the darkened one). Upon entering the darkened box the rats were locked in and given a five second electric shock delivered through the metal grid on the floor. Although the rats learned to avoid the dark box very quickly, Ungar continued to run trials on these same rats for several days so that a good supply of a ‘fear of the dark’ chemical was produced in their brains. Mice that were injected with brain extract from these trained rats were more likely to avoid the dark than those that had been injected with brain extract from normal rats. Between 1965 and 1975, there were 105 positive replications of this experiment by other scientists and only 23 negative replications. Ungar believed that these negative replications occurred as a result of scientists clearly departing from his exact procedures. In the late 1960s, McConnell and other experimenters taught rats more complex tasks such as choosing a left or right turn in an alley in order to obtain food – such tasks seemed to be transferable among rats as well as other creatures such as cats, cockroaches, the praying mantis, and goldfish (chemical transfer of memory was sometimes also found to be successful between two different species).

Ungar wanted to isolate, analyze, and synthesize active molecules. That is to say, Ungar wanted to find some reproducible transfer effect (such as fear of the dark) and study the chemical that was responsible for it – the ‘fear of the dark’ chemical that he set out to find became known as scotophobin, and in order to obtain a measurable amount of it he required the brains of 4000 trained rats. This was such an expensive scientific endeavor that other biochemists could not compete with Ungar. Eventually, he believed he had isolated the scotophobin molecule. After analyzing it and discovering its chemical structure (it was a peptide comprised of 15 amino acids), he believed he was able to chemically synthesize the molecule in the lab. Ungar had hoped that the availability of the synthetic version of this molecule would solve the problem of repeating the expensive chemical transfer experiments. A large number of experiments using synthetic scotophobin were completed – however, there were disputes over the purity of the synthetic material as well as its stability, over the way it was kept by other labs before it was used as well as the kind of behavior changes it induced (if any at all). To complicate matters, Ungar announced several alterations to the precise chemical structure of the scotophobin molecule.

McConnell closed his lab in 1971 because he was unable to obtain further funding for his research; Ungar on the other hand continued with his experiments. Training thousands of rats proved too costly, and as a result Ungar turned his attention to goldfish (goldfish are good at color discrimination and are relatively inexpensive). Roughly 17000 trained goldfish were needed to produce 750 grams of brains – however, this proved to be an insufficient amount for him to identify the chemical structure of the ‘color discrimination’ memory substance. Ungar, who was of normal retiring age when he began his work on memory transfer, died in 1977 at the age of 71 – and the entire field died with him for two reasons. Firstly, there was not enough reliability in the “chemical transfer of memory” effect to make the experiments attractive to a beginning researcher. It would be too risky for someone who was just “starting out”. Secondly, the investment required to make a serious attempt at repeating Ungar’s work was too high financially.

Ungar’s report of his analysis and synthesis of scotophobin was published in Nature, arguably the most prestigious journal in the field of biology. However, accompanying it was a report written and signed by the referee of the journal that criticized Ungar’s findings (it is worth mentioning that Ungar’s research article was five pages in length while the referee’s critical report was fifteen pages in length). It is probable that this significantly reduced the credibility of the memory transfer phenomenon from the very beginning – yet even today, there remains no published research containing decisive technical evidence that disproves memory transfer.

QUESTIONS

1) McConnell claimed that only certain skilful people such as himself who understood the worms well enough to properly train them would be able to obtain the “correct” results. Is this a valid argument in the field of science?

2) Many scientists were unable to reproduce McConnell’s results of the worm experiments. Up to 70 variables (or “excuses” according to the critics of McConnell) were cited at one time or another to account for discrepancies in experimental results. Examples of some of the variables mentioned were the strength and color of the lights, the strength and polarity of the electric shocks, and the frequency of training. However, other variables mentioned included: the season of the year; the time of day when the worms were trained; the barometric pressure; the phase of the moon; and the orientation of the training trough with respect to the earth’s magnetic field! In reality, science experiments are not (and in some cases cannot) be controlled for these extreme variables – but they are variables nevertheless. Does the fact that there are virtually an infinite number of potential variables mean that science is in fact fallible and “untidy”, and that it carries merely an illusion of perfect methodology and logic?

3) There were 105 positive replications of Ungar’s most famous experiment (transferring the ‘fear of darkness’ trait from rats to mice) compared to only 23 negative replications. However, the sheer number and weight of the positive experimental replications was not enough to persuade the scientific community to believe in such unorthodox and shocking findings. Does this mean that scientists’ personal attitudes and biases interfere with the objective and “scientific” way in which they should all ideally be thinking?

4) The scientific journal Nature has published other critical reports (such as the one that accompanied Ungar’s research paper) on other studies deemed to be “fringe science”. Ultimately, is this advantageous or disadvantageous to science? What role should scientific journals play in science?

5) Even today, there is no published research containing conclusive evidence that disproves the chemical transfer of memory. Is it easier to prove a scientific theory than it is to disprove a scientific theory?

6) What are the ethical implications of the chemical transfer of memory? Should such research be funded?

REFERENCES:

Collins, H. and Pinch, T. (1993). The Golem: What Everyone Should Know About Science. Cambridge University Press.

Garfield, E. (1975). Using the SCI to Illuminate Scotophobin. [WWW document]. URL:

http://www.garfield.library.upenn.edu/essays/v2p366y1974-76.pdf (2002/01/12).

McConnell, J.V. (1962). Memory transfer through cannibalism in planarians. Journal of Neurophysiology, 3, 42 – 8.

Ungar, G., Galvan, L., and Clark, R.H. (1968). Chemical transfer of learned fear. Nature, 217, 1259 – 61.

Ungar, G., Desiderio, D.M., and Parr, W. (1972). Isolation, identification and synthesis of a specific- behavior-inducing brain peptide. Nature,

238, 198 – 202.