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Photo of James McGaugh Remembering What Matters

This story profiles the work of James McGaugh, who has found a strong relationship between emotional experiences and memory. and also discovered that memory may be enhanced an manipulated. Following the premiere of the Scientific American Frontiers Special Pieces of Mind, James answered viewers' questions as part of an Ask the Scientists panel. Here are viewers' questions and his answers:



QBeautiful work so far, but I don't understand how you are able to distinguish the ability of epinephrine to enhance learning from its ability to heighten receptivity. In other words we are aware that certain medications can dull receptivity and thus appear to interfere with memory/learning. Why is the epinephrine not just heightening alertness. And also how did you eliminate the effects of state-dependent learning. The show did not address this. Finally, and mixed in with the above, how do you distinguish heightened receptivity from improved memory?

These are excellent questions! You are, of course, quite correct in indicating that drugs and hormones can have many effects on sensory, attention and other processes and that if subjects are tested while under the influence of the treatments it is difficult to distinguish these effects from effects on memory. In our experiments with animal subjects we administered the drugs and hormones (including epinephrine, or adrenaline) AFTER the animals were trained. And we tested the animals memory no sooner than a day later (sometimes even a month later). Thus, the treatments we administered are not present during either training or subsequent testing. Treatments administered immediately after training enhance memory. Treatments administered several hours after training have no effect.

Such findings indicate that the drugs and hormones affect memory by influencing post-learning processes involved in storing new information in the brain. Because the treatments are not present DURING learning the cannot act to influence memory (in our studies with animal subjects) by affecting sensory processes, or attention. Additionally, such studies rule out "state-dependent" effects of the treatments because the animals are in the same state (i.e. untreated) when they learn and when they are subsequently tested. In the experiments with human subjects we have not, as yet, used "post-learning" treatments. But the beta-blocker that prevented the effects of emotional arousal on long-term memory did not impair the learning of non-arousing material. Thus, we think that the same processes are operating in animal and human subjects. Of course, additional experiments will provide added clarification. If you are interested I would be pleased to provide references to published papers that discuss these issues in more detail and provide the critical evidence.



QDoes your research support adventure-based or experiential learning techniques such as ropes courses, and other simulations which arouse the emotions of participants while learning new tools and techniques?

An implication of our research is that experiences that are emotionally arousing (within limits, of course) should result in strong memories. To my knowledge, this implication has not been examined in the context of experiential learning courses. Most of the research with human subjects has focused on memory for events -- not memory for techniques or skills. There is much research that could be done on this problem.



QIt is often said that students study by cramming for a test, but walk out and never remember the information. Your studies indicate emotions play an important role in memory. Any advice for developing better memories in the classroom?

The best advice that I know is that one should pay attention, sustain interest and take notes!!! But, of course, our findings suggest that the neurobiological consequences of emotional arousal regulate the strength of memories and, by implication, affect memory for classroom experiences. This issue has not been examined experimentally, as yet.



QWith your research into emotional linkage to memory, have you touched upon those memories that are set linked with a particular sound, smell, taste, sight or touch? Personally, I remember a moment when I was 2 years old, having moved into my parent's new house and my mother made tea for me to drink. It was right on a pullout tray from the cupboards besides the stove. Yet, my mother doesn't remember it at all. Also, from another person, who was 9 months old when his parents were in a protest where tear gas was fired into the crowd, he claims that he remembers the smell of the tear gas. Are these mechanisms where the primitive brain stem attaches importance to our memories? Is there any research into this storage of memory? Any way to determine the truthfulness of our memories that are associated with these smells/touches/sights/sounds/tastes?

You are on to something important. There is tantalizing evidence suggesting that smells and tastes make particularly strong associations linked to experiences. The distinguished writer Proust ("Remembrance of Things Past") wrote compellingly about smell and memory. Much contemporary research investigating neurobiological bases of learning and memory uses smells and tastes as cues in learning experiments. Studies of conditioned taste aversion, in particular provide strong support for your suggestions.



QI was fascinated by the info on emotion helping memory. Where can I find more info on this topic. The TV program was a good teaser. Are there any WEB sites or books on the topic?

The following references might be of interest:

Cahill, L. and McGaugh, J.L. Modulation of Memory Storage. Current Opinion in Neurobiology, 1966, 6, 237-242.

McGaugh, J.L. Emotional activation, neuromodulatory systems and memory strength. In: Memory Distortion: How Minds, Brains and Societies Reconstruct the Past. D.L. Schacter, J.T. Coyle, M-M Mesalum and L.E. Sullivan (Eds) Cambridge, M

Harvard University Press, 1995, pp 255-273.

McGaugh, J.L. Hormones and memory, The Encyclopedia of Learning and Memory, New York, Macmillan Publishing Co. 1992, pp 248-250.

McGaugh, J.L. Memory consolidation, The Encyclopedia of Learning and Memory, New York, Macmillan Publishing Co. 1992, pp 395-398.

McGaugh, J.L. Affect, neuromodulatory systems and memory storage. In S.-A. Christianson (Ed), Handbook of Emotion and Memory: Current Research and Theory, Hillsdale, HNJ: Lawrence Erlbaum Associates, 1992, pp 245-268.

Schacter, D.L. Searching For Memory, New York, Basic Books, 1996.

Le Doux, J. The Emotional Brain, New York, Simon and Shuster, 1996.



QWhat are the implications of the findings reported in the program as the apply to the use of beta blockers in the control of hypertension?

Our findings suggest that beta blockers selectively dampen the effects of emotional arousal (and the hormonal consequence) on the formation of new memories. The formation of normal memory does not appear to be affected. However, this issues needs further study before it can be concluded with any degree of certainty that beta blockers do not impair memory for ordinary experiences.



QCould there be a relationship between what you have found and the problems older people seem to have in recalling recent events? Could adrenaline help Alzheimer's patients?

Our findings simply indicate that beta blockers mute the effects of emotional arousal on memory strength. We would expect that such effects might be seen in anyone taking beta blockers whether they are young, middle-aged or elderly. We do not know whether the effects are greater in the elderly. Drugs having such effects include those affecting what are called beta 1 or beta 2 adrenergic receptors. In laboratory animals there is clear and extensive evidence indicating that adrenaline administered immediately after learning enhances long-term memory (in young as well as aged rats and mice).

The effects of adrenaline on memory in Alzheimer's patients has not been investigated. However, it is known that adrenaline induces the release of glucose. And, Dr. Paul Gold in the Psychology Department of the University of Virginia has found that glucose enhances memory in elderly human subjects as well as animal subjects.



QWhy do some people have no memory of a traumatic or painful event? I have heard that hypnotism can surface these memories in an individual.

A simple answer is that we do not know what may cause traumatic amnesia. But, it could be that is, at least under some conditions, due to an over-activation of stress hormone systems. Our studies with rats and mice indicate that very high doses of adrenaline impair or block memory formation. Such memories cannot be retrieved or surfaced simply because they are not formed. The evidence suggesting that hypnosis can aid memory retrieval is weak, at best. A problem with efforts to induce recall by hypnosis is that subjects simply tend to be more talkative - and what they talk about does not necessarily indicate that they have reliable memories.



QMy anatomy class recently watched the experiment done with the swimming rats and their ability to remember where the underwater platform was. Our question is this: Why was the rat given the adrenalin blocking injection after he was removed from the water rather than before? In the human studies, the blocker was given before the subjects viewed the slide show depicting the accident.

An excellent question! I answered it, in part, in my answer to a previous question. In the animal experiments the drugs or hormones were administered after training because we wanted to influence brain memory-storage processes that are initiated by training and which remain susceptible to modifying influences for perhaps an hour or two after training is completed. Additionally, when such procedures are used (e.g. drug or hormone administration after training) it cannot be argued that the treatments directly affected performance during training or retention testing.

The human experiment used drug administration before the experiment simply for convenience (and because we already had the findings from animal experiments). In that experiment the drug (a beta-blocker) selectively blocked the effect of emotional arousal on subsequent long-term memory. That is, the drug did not otherwise impair memory. Clearly, additional studies with human subjects are needed to investigate the effects of post-learning administration of drugs and hormones.



QIn his book "Neural Darwinism," Edelman says something like ..."...true learning occurs when there is surprise, or violation of expectation..." (I recall he was summarizing work by Staddon and others.) "Surprise" is something that can be figured, for simple alternatives, using Shannon's theory of information. In fact, the quantity plnp is termed "surprise." Does the amount of adrenaline map to the amount of surprise, measured as Shannon et al. would measure it?

Learning requires, of course, new experiences (by definition). But although surprise or emotional arousal appears to enhance learning, and memory, it is not at all clear that learning requires surprise (in the emotional sense of that word). Of course, if the word, "surprise" is taken to mean the same as, "new information" then that is a definitional issue, not an experimental question. The amount of new information required to induce learning or the amount of adrenaline required to potentiate learning has not been quantified. We do have experimental findings that indicate the dose of adrenalin to produce the amount of learning induced by a single training trial -- at least under very specific experimental conditions.




 

Scientific American Frontiers
Fall 1990 to Spring 2000
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