Expression of IGF-2 Receptor in the Auditory Cortex Improves the Precision of Recent Fear Memories and Maintains Detailed Remote Fear Memories Over Time.

Traumatic memories may become less precise over time and lead to the development of fear responses to novel stimuli, a process referred to as time-dependent fear generalization. The conditions that cause the growth of fear generalization over time are poorly understood. Here, we found that, in male rats, the level of discrimination at the early time point contributes to determining whether fear generalization will develop with the passage of time or not, suggesting a link between the precision of recent memory and the stability of remote engrams. We also found that the expression of insulin-like growth factor 2 receptor in layer 2/3 of the auditory cortex is linked to the precision of recent memories and to the stability of remote engrams and the development of fear generalization over time. These findings provide new insights on the neural mechanisms that underlie the time-dependent development of fear generalization that may occur over time after a traumatic event.