Pavlov’s Power

Pavlov’s Power is the third chapter in Jo Marchant’s “Cure:  A Journey Into the Science of Mind Over Body.”  Remember Pavlov the Russian physiologist who discovered classical conditioning?  Pavlov is the one who discovered that by pairing a stimulus, a bell for example, with the presentation of food caused the dog to salivate when the stimulus alone, called the conditioned stimulus, was presented.  Classical conditioning is one of the fundamental paradigms in psychology.  The question is, does this procedure have any practical uses.  The subtitle of this chapter, How to Train Your Immune System, provides the answer.

Attention deficit hyperactivity disorder (ADHD) describe children who are inattentive, hyperactive, and impulsive.  They are constantly  talking and fidgeting.  unable to wait for their turn, and are unable to focus in school.  Medication helps them to control their symptoms, but still causes problems from irritable outbursts when the drug wears off  to weight loss and stunted growth.  A researcher name Sandler wondered whether a placebo might help these children to manage their symptoms on a lower dose of the drug.  He hoped that the honest delivery of placebos as part of a regime that would harness the power of both expectation and conditioning.   He employed seventy ADHD patients aged six to twelve in a two month trial.  These children were split randomly into three groups.  One group underwent a conditioning regime in which they received their normal medication, but also swallowed a distinctive green and white capsule along with their drug.  For the second month they received half their usual drug along with the placebo capsule.  There were two control groups, neither of which received any conditioning.  One group received their full dose of medication for the first month and a half dose for the second month.  The second control group received the full dose of medication for two months.

Sandler published his results in 2010.  The symptoms of the half-dose control group got significantly worse in the second month of the trial.  However, the conditioned group remained stable, doing just as well as the full dose patients.  There were even hints that the children in this group did even better, suffering fewer side effects than those on the full dose of the drug.

Bob Ader, a psychologist at the University of Rochester was doing research on taste aversion.  He gave a group of rats several doses of water sweetened with saccharin.  Normallt this would be a treat but he paired the water with injections that made the animals feel sick.  Later when the rats are given sweetened water on its own, they associated the sugary case with feeling ill (classical conditioning) and refused to drink it.  Adler then forced-fed them using an eyedropper to see how long it would take to learn to forget the negative association.  Rather than forgetting the negative association they died, one by one.

The drug that was used to make the rats feel sick was cytoxan.  In addition to causing the feeling of sickness, it also suppresses the immune system.  So conditioning reaches far behind normal responses, it can also affect the immune system.  This is a rather dramatic conclusion to draw, and it was not accepted at first.  David Felten, a neuroscientist working at the University of Indiana used a powerful microscope to look at the body tissues from dissected mice.  When Felten followed the different branches of the autonomic nervous he found nerves running right into the hear of immune organs such as the spleen and thymus.

Many scientists found Felten’s results difficult to accept.  However, one who did not was Dr. Jonas Salk, the creator of the Salk vaccine.  Salk wrote, “This research area could turn out to be one of the truly great areas of biology in medicine.  You’ll meet some opposition.  Continue to swim upstream.”

Felten did and stated a collaboration with Ader and his colleague Cohen and moved them to the University of Rochester.  These three are now broadly credited with founding a field of research known as psychoneuroimmunology.  This group went on of discover a complex web of connections.  They found receptors for neurotransmitters—messenger molecules produced by the brain— on the surface of immune cells, as well as new neurotransmitters that could talk to those cells.  The lines of communications went in both directions.  Psychological factors can trigger the release of neurotransmitters that influence immune responses, while chemicals released by the immune system can influence the brain.  For example drowsiness, fever and depressive symptomjtr that confine us to bed when we are well.

So Pavlovian conditioning can go way beyond making dogs drool!


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