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Removing Fear Memories
Disruption of reconsolidation of an activated fear memory prevents subsequent fear expression. After a memory reminder, extinction training can disrupt fear memory. In rodents, this process is dependent on a brain area called the amygdala. Agren et al. (p. 1550) used functional magnetic resonance imaging and a fear conditioning paradigm to show in humans that, after an associative fear memory was formed, reactivation and reconsolidation left a signature in the basolateral amygdala. This memory trace predicted later fear expression, which was linked to activity in areas forming the fear circuit of the brain. Extinction alone did not change this signal. However, extinction in the reconsolidation window blocked fear expression by erasing the fear memory trace in the amygdala and weakened the connection in the wider fear circuit of the brain.
Abstract
Memories become labile when recalled. In humans and rodents alike, reactivated fear memories can be attenuated by disrupting reconsolidation with extinction training. Using functional brain imaging, we found that, after a conditioned fear memory was formed, reactivation and reconsolidation left a memory trace in the basolateral amygdala that predicted subsequent fear expression and was tightly coupled to activity in the fear circuit of the brain. In contrast, reactivation followed by disrupted reconsolidation suppressed fear, abolished the memory trace, and attenuated fear-circuit connectivity. Thus, as previously demonstrated in rodents, fear memory suppression resulting from behavioral disruption of reconsolidation is amygdala-dependent also in humans, which supports an evolutionarily conserved memory-update mechanism.
