Reversing Extinction Without Retraining Reinstate CS Without

Reversing Extinction Without Retraining

Reinstate CS without U.S.

The association between a conditioned stimulus (CS) and an unconditioned stimulus (U.S.) is believed to be the result of synaptic connections that formed during the pairing of the CS and U.S.. Extinction training had therefore been proposed to represent the dissolution of these connections (reviewed in Gupta, Vig, Noelle, 2011). However, a large body of evidence argues against this model and suggests conditioning and extinction represent two functionally distinct neurobiological systems; one for the acquisition of an CS-U.S. association and the other capable of inhibiting this association. This would explain the phenomenon of 'savings', which represents the ability of a response to be restored with little effort after extinction training. The second model also explains why a second round of extinction training takes less time to work. The neuronal connections that were formed during the CS-U.S. pairing therefore remain intact, even after extinction training, and the neuronal connections formed during extinction training remain intact even if the conditioned response reemerges.

Overcoming Extinction without U.S. Retraining

There are two well researched phenomena that can restore a conditioned response without relying on reexposures to the U.S. These are spontaneous recovery and renewal (reviewed in Gupta, Vig, Noelle, 2011). Spontaneous recovery is defined by the reemergence of the response with the passage of time, supposedly as the effects of extinction training wear off. Renewal occurs when the animal experiences a significant shift away from the environmental context in which the extinction training took place.

An example of spontaneous recovery was recently published by Thanellou and Green (2011). Rats were conditioned to blink their eyes in response to an eye shock (U.S.), which was paired with an audible tone. The rats were then put through three sessions of extinction training. During the interval between the three extinction training sessions there was significant recovery of the conditioned response, indicating spontaneous recovery had occurred. By the end of each extinction training session the response had been fully extinguished.