Significant life events and the shape of memories to come: a hypothesis.

Much has been said about how significant life events modulate our response to stimuli that are integral to those events. However, we know less about the more general consequences of these events, that is, how they affect subsequent learning abilities that are seemingly irrelevant to the initial event. Here, it is proposed that significant life events, most often stressful in nature, alter future learned responses by inducing nonspecific and persistent changes in neuroanatomical structures. These changes are induced in the presence of sex and stress hormones, which are released either in response to the event itself or as a consequence of stages of life. To illustrate, the effects of acute stressful experience on learning processes and their regulation by the release of hormones are reviewed. I discuss how these events and their hormonal consequences alter anatomical substrates such as those involved in neurogenesis and synaptogenesis. It is proposed that these modulatory processes allow past experiences to change the shape of memories to come. In this way, memorable life events become less about the past and more about the future.