Ontogeny of memory: An update on 40 years of work on infantile amnesia.

Given the profound influence that early life experiences can have upon psychosocial functioning later in life, it is intriguing that most adults fail to recall autobiographical events from their early childhood years. Infantile amnesia is the term used to describe this phenomenon of accelerated forgetting during infancy, and it is not unique to humans. Over the years, information garnered from animal studies has provided clues as to the neurobiological basis of infantile amnesia. The purpose of this review is to provide a neurobiological update on what we now know about infantile amnesia since the publication of Campbell and Spear's seminal review on the topic more than 40 years ago. We present evidence that infantile amnesia is unlikely to be explained by a unitary theory, with the protracted development of multiple brain regions and neurotransmitter systems important for learning and memory likely to be involved. The recent discovery that exposure to early life stress can alleviate infantile amnesia offers a potential explanation as to how early adversity can so profoundly affect mental health in adulthood, and understanding the neurobiological basis for this early transition may lead to the development of effective therapeutic interventions.