ABOVE: In the basolateral amygdala of a mouse brain, newly formed fear-extinction memory cells (orange) can override the animal’s past memory of a foot shock.
© XIANGYU ZHAN
The paper
X. Zhang et al., “Amygdala reward neurons form and store fear extinction memory,” Neuron, 105:1077–93, 2020.
Fear conditioning, which connects a neutral stimulus with a painful experience in an animal’s brain, can be undone. Put a mouse in a cage where it experienced foot shocks the day before, and its initial response of freezing in place will eventually dissipate once the shock stimulus ceases. While scientists have known about such fear extinction for a long time, they haven’t understood how it happens in the brain.
One hypothesis, says Susumu Tonegawa of MIT, is that a new memory takes the place of the fearful one: the original memory remains intact, but it’s inhibited by the new one. Under certain circumstances, the conditioned ...
