Oct. 6, 2003 WASHINGTON -- Behavior therapists may have a better way to help anxious patients, thanks to insights from a UCLA study of different ways to get mice past their fears. Rodents have long been used to study learning by association. Neuroscientists compared different ways of exposing mice to a stimulus that they had learned to fear, and found that "massing" the feared stimulus -– delivering it in concentrated bursts, not pacing it with longer pauses in between -- was surprisingly efficient at helping to erase its impact. This study appears in the October issue of the Journal of Experimental Psychology: Animal Behavior Processes, which is published by the American Psychological Association.
According to the authors, doctoral students Christopher Cain and Ashley Blouin, and Mark Barad, M.D., Ph.D., these findings are significant for clinical behavioral therapy, which has been scientifically proven to work in a range of human anxiety disorders, including specific phobias, panic disorder, social phobia, post-traumatic stress disorder, and obsessive-compulsive disorder.
At the University of California, Los Angeles, the researchers taught mice (in most conditions, eight at a time) to fear harmless white noise by associating it with a mild shock delivered through the floor of the experimental cage. After a couple of trials, the mice "froze" –- just stopped moving, a fear response –- for about 72 seconds, or 60 percent of the two minutes of white noise. Thus, the white noise became what's called a "conditioned stimulus." It may not have been the original source of pain, but it became sufficiently associated with pain to cause fear all by itself.
Next, Cain and his colleagues separated the mice into three groups and measured how well they overcame their aversion to white noise when they heard it 20 times for two minutes each, without shocks -– with intervals of six, 60 or 600 seconds between each presentation. Repeatedly presenting a conditioned stimulus has long been known to "extinguish" a fear by exposing animals (including humans) to that stimulus without associated pain. In the study, for example, some of the mice learned to trust that white noise would not come with shocks. In a human parallel, someone who had developed a fear of dogs after being bitten could be exposed to playful, gentle dogs as a way to re-learn that most are safe.
The only catch is that anxiety is like an unwanted houseguest: It breezes in quickly, without invitation, and is hard to kick out, as is clear from the fact that the mice feared the white noise after two exposures, but needed far more than two exposures to get over it –- and only under certain conditions. Thus, approaches that make treatment more efficient are high on therapists' wish lists.
Cain and his colleagues found that both short-term and long-term fear extinction (immediate and one day later) were greater with "temporally massed" presentations of the stimulus, which had six-second intervals between each of the 20 bursts of white noise. The six-second-gap mice stopped showing significant freezing after about 10 presentations of white noise, or 20 minutes' worth. The mice in the other two groups never really stopped freezing.
Given these important findings, the authors say, "Therapists may wish to incorporate some massing of anxiogenic stimuli into exposure therapy sessions to more quickly reduce the aversiveness of therapy and increase the patient's willingness to continue with treatment."
"This very strong finding," says co-author Mark Barad, M.D., Ph.D., "is already inspiring a search for a similar pattern of response in human anxiety patients. It's part of a recent wave of important discoveries about fear extinction, findings that will transform both the practice of behavior therapy and the use of drugs as adjuncts to psychotherapy in the next few years."
Article: Christopher K. Cain, B.A.; Ashley M. Blouin, B.A.; Mark Barad, M.D., Ph.D., "Temporally Massed CS Presentations Generate More Fear Extinction Than Spaced Presentations," Journal of Experimental Psychology: Animal Behavior Processes, Vol. 29, No. 4.
(Full text of the article is available from the APA Public Affairs Office and at http://www.apa.org/releases/conditionalfear_article.pdf)
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