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Saturday, May 30, 2009

A New Treatment for Phobias and Emotional Trauma?

I have mentioned earlier the recent discovery that when a memory is recalled, it is then re-saved ("consolidated," as researchers llke to say). During that reconsolidation time window, which in rats is about 6 hours, the memory becomes vulnerable to new information and interference, and can become distorted or even abolished.

Researchers have discovered that injecting a beta blocker drug during this reconsolidation period can prevent re-consolidation of the memory that was recalled, and this is an effective therapy for some patients. The problem is that this is a prescription drug and is potentially toxic.

Another approach is to use extinction therapy. Most phobias and emotional traumas arise from a conditioned association between a neutral stimulus and the traumatic event, much like the conditioning discovered by Pavlov and his dogs. If one repeats the conditoning cue, without re-presenting the bad event, the patient may develop a new memory in which the cue becomes innocuous because it is no longer associated with the bad event. The problem here is that the effect can wear off over time, because the original fear memory was never erased.

A new approach has been devised by Marie Monfils, Joseph LeDoux, and colleagues at several neuroscience and psychiatric institutions. Their idea capitalizes on the differences between reconsolidation and extinction. They reasoned that if the non-threatening conditioning stimulus were given deuring the reconsolidation window, a new memory that the situation was safe would be formed. Use of a drug could be avoided.

They tested this idea in rats that were trained to be fearful by pairing a tone cue with electric shock to the feet.This was done three times. The intervention therapy consisted of testing for recall with the tone cue, followed by a series of extinction trials in which the cue was repeatedly delivered without accompanying foot shock. Some rat groups were given the intervention during the window and others outside it, like the next day. The behavioral response of fear was movement freezing. That is, when the tone was sounded, rats indicated their memory of the training by freezing out of fear.

The day after the extinction session, all groups showed a similar abolition of freeze behavior. Extinction worked, but did it last? A month later, the same rats were tested again, and the freeze behavior had returned in all rats except those that had received the neutral cue and extinction training during the reconsolidation window. Multiple other experiments supported the value of this intervention approach.

The investigators are now exploring clinical implications in human psychotherapy. There is a possible negative consequence. Erasing the phobia may be accompanied by the conditioning stimulus acquiring the status of being safe and not just neutral. Studies on humans can also allow experimenters to study not just the behavioral expression of fear but also allow them to examine the thought processes. The fear memory may still be there, with the major change being in the behavioral expression.

Monfils, M.-H. et al. 2009. Extinction-reconsolidation boundaries: key to persistent attentuation of fear memories. Science. 324: 951-955.

Saturday, May 16, 2009

There's a Reason for School Recess

Even when I was a kid, people said that being physically active could help you perform better in school. But this was mostly anecdotal, with very little research evidence. Now there is some evidence.

Charles Hillman and colleagues at the University of Illinois recently reported a study on the effects of exercise on cognitive function of 20 preadolescent children aged 9 to 10. They administered some stimulus discrimination tests and academic tests for reading, spelling and math. On one day, students were tested following a 20-minute resting period; on another day, students walked on a treadmill before testing. The exercise consisted of 20 min of treadmill exercise at 60% of estimated maximum heart rate. Mental function was then tested once heart rate returned to within 10% of pre-exercise levels. Results indicated improved performance on the tests following aerobic exercise relative to the resting session. Recordings of brain responses to stimuli suggested that the difference was attributable to improved attentiveness after exercise.

Note that this is just from a single aerobic exercise experience. How can that be beneficial? The most obvious explanation is that exercise generates more blood supply to the brain, but I don't know that this has been documented with MRI studies, for example. Actually, what is known is that exercise diverts blood to the muscles. The generally accepted view is that the body tightly regulates blood flow to the brain and that the brain always gets what it needs. Another possibility is that exercise relieves anxiety and stress, which are known to disrupt attentiveness and learning. Maybe the repetitive discipline of exercises like treadmill walking help entrain the brain into a more attentive mode. We need a study that compares tradmill walking with a different kind of exercise regimen (like a vigorous and competitive basketball game, for example).

As for what goes on in a typical school recess, I doubt that such activities as shooting marbles, gossiping, or whatever else goes on these days with kids at recess, really helps school work. Gym class might be another matter, but unfortunately many schools do not provide a meaningful gym class. Some of the authors' suggestions don't seem to be supported by this particular research. For example, they advocate:

• scheduling outdoor recess as a part of each school day (recess does not typically provide aerobic levels of exercise)

• offering formal physical education 150 minutes per week at the elementary level, 225 minutes at the secondary level (again, the beneficial effects likely come from aerobic levels of exercise, not just any exercise)

• encouraging classroom teachers to integrate physical activity into learning (this almost certainly will not be at aerobic levels of exercise.)

There is the also the issue of a continuing aerobic exercise program, which presumably could produce long-lasting beneficial effects in young children. My own prejudice is that schools and parents ought to get serious about requiring an aerobic exercise program for kids. It should not only improve the quality of school work but also help combat the epidemic of obesity and diabetes. One caveat: running to achieve aerobic levels of exercise may not be advisable in children. My own experience with jogging, for example, might have been great for my heart and brain, but I now have two artificial kness to show for it.

If exercise is so good for academic performance, why do varsity athletes generally make poorer grades than their classmates? Well, there are many other factors, of course. One prevailing attitude among athletes is that academics are less important to them than their sport. Their peers idolize athletic stars. Students who make all As are not considered heroes; they are considered nerds or otherwise abnormal. Athletes devote their time and energy to their sport, not school work.


Hillman, C. H., et al. 2009. The effect of acute treadmill walking on cognitive control and academic achievement in preadolescent children. Neuroscience. 31;159(3):1044-54.