Erasing Memories

Let’s say you were in a terrible automobile accident that left you traumatized. Now whenever you get into an automobile you feel an overwhelming fear come over you. In today’s world this would probably pose problems so you’d seek out behavioral therapy to get rid of the fear of automobiles. Most likely, the behavioral therapist would provide you with repeated controlled exposures to automobiles without any traumatic event. Over time your fear of automobiles would go away.

However, as the authors of “Calcium-Permeable AMPA Receptor Dynamics Mediate Fear Memory Erasure” (published November 19, 2010 in Science) point out, sometime this effect is permanent and sometimes it isn’t. They set out to understand the cellular and molecular mechanisms underlying the erasure of fear memory.

The amygdala is well known to be an important brain nucleus associated with fear. The research team focused on thalamic synapses on lateral amygdala neurons that increase their strength on the creation of a fear memory. To erase the fear memory the synaptic strengths would need to decrease. They showed an increase in the number of a calcium permeable receptor known as the CP-AMPA receptor in these synapses after fear conditioning and a peak in the number at 1 day after the event. They also showed that the CP-AMPA receptor increases the capacity for synaptic weakening. Based on these findings they hypothesized that fear erasure could best be achieved around 24 hours after the fear event.

Through behavioral testing, the research team confirmed that changes in synaptic properties during at about 1 day in mice “render the permanence of recent memory highly reversible.” It’s this period after the the event (the timing may be different in humans) that probably provides the best point for intervention in alleviating traumatic memories.