Learning To Unlearn Fear: A Novel Animal Model Of Exposure Therapy

Document Type


Publication Date


Published In

Neuroscience 2014


The effect of extinction in laboratory animals, like the effect of exposure therapy in humans, is temporary and with passage of time fear often recovers. In a recent experiment we used a modified extinction procedure in which, 24 hr after contextual fear conditioning, animals were returned to the apparatus in the absence of shock. In contrast to the typical extinction procedure, the return was brief and the animals were removed from the apparatus before they had an opportunity to extinguish the fear, that is, they were removed either at the onset of weak (incipient) fear (30-sec exposure) or at the peak of intense (incubated) fear (120-sec exposure). A retention test revealed that the 30-sec exposure, not the 120-sec exposure, was effective in reducing retention of fear. To account for these results we suggest that the brief (30 sec) exposure, in addition to initiating retrieval of fear, itself serves as a learning experience (that is, during the brief exposure the conditioning chamber may be associated with retrieved fear). Thus, because retrieved fear during the 30-sec exposure is relatively weak, the 30-sec exposure results in weak conditioning and weak retention the next day; because retrieved fear during the 120-sec exposure is relatively strong, the 120-sec exposure results in enhanced conditioning and strong retention. To test this hypothesis, in the present study, we added a second 30-sec exposure to the first: If the brief exposure procedure indeed serves as a learning experience, then adding the second 30-sec exposure should increase the effectiveness of the procedure in reducing retention of fear. Male Long-Evans rats underwent contextual fear conditioning followed 24 hr later by the brief exposure procedure; a retention test was administered either 1 or 13 days later. Fear conditioning consisted of placing rats in a dark compartment for 120 sec followed by a single shock (0.8 mA, 0.5 sec); the brief exposure procedure consisted of confining the animals to the dark compartment for either a single 30-sec exposure or for two 30-sec exposures separated by 10 min; the retention test consisted of returning the animals to dark compartment for 180 sec. The results indicated that the additional 30-sec exposure increased the effectiveness of the procedure in reducing retention of fear both in the short term (24 hr) and the long term (13 days). Thus, the present study suggests that, in contrast to the typical extinction procedure, the brief exposure procedure may be more effective in limiting recovery of fear. Viewed from a therapeutic perspective, these results have implications for the efficacy of a modified exposure therapy protocol in the treatment of pathological fear memory.


Society For Neuroscience 2014 Annual Meeting

Conference Dates

November 15-19, 2014

Conference Location

Washington, DC