Fig. 1. Spontaneous recovery experiment.

Presentation of an isolated retrieval trial, one hour later followed by an extinction phase, does not prevent spontaneous recovery. All sessions were conducted in context A. Rats were conditioned with 3 tone-shock pairings. Twenty-four hours later, they were exposed to a single retrieval tone (Ret group, n = 8) or context only (NoRet group, n = 8), followed one hour later by an extinction phase consisting of 18 or 19 tones, respectively. Twenty-four hours after extinction training, long-term memory was tested by presenting 4 tones. One month later, spontaneous recovery was evaluated with 4 tones. In contrast to the original Monfils et al. paper, we observed spontaneous recovery already one day after extinction. In addition, trial-by-trial analyses indicate a significant return of fear, in both groups, from the end of the long-term memory test to the start of the spontaneous recovery test one month later. Our data do not support an attenuation of spontaneous recovery in the Ret group as compared with the NoRet group. Freezing during each tone presentation is shown as mean + SEM, ^# indicates p < .05 and * indicates p < .01. Ret = retrieval, d = day, h = hour.