Good memories of bad events in infancy

If a helpless newborn infant does not form an attachment to its care-giver, even an abusive one, its chances of survival diminish, so evolution should strongly favour attachment by the infant, regardless of the quality of care-giving(1). As a part of the brain called the amygdala is critical for learned fear in adult animals(2, 3, 4), we investigated whether the development of learned avoidance behaviour could be delayed by late maturation of amygdala function. We found that very young rat pups exposed to various odours associated with shock treatment learn an approach response to that odour, whereas older pups learn odour avoidance. We show that the origin and development of learned odour-avoidance behaviour is associated with enhanced neural responses in the amygdala during odour-shock conditioning.