Mild hypothermia can disrupt extinction learning but not original conditioning.

Using a retrograde amnesia procedure, the susceptibility of the extinction of fear conditioning was assessed in two experiments. Extinction of a passive-avoidance task was impaired by a body-cooling treatment (e.g., hypothermia; [7]) which was too mild to induce amnesia for the avoidance training, suggesting that the memory for extinction is more susceptible to body cooling than the memory for the initial fear conditioning. Decreasing the severity of the treatment decreased its ability to disrupt extinction. Thus, the study demonstrates a difference in the vulnerability to amnesia of fear conditioning vs. extinction of that fear.