The human brain undergoes complex and life-long changes especially at specific stages of development and this process is called maturation. It is a process of brain development in which minor modifications are made to improve the brains efficiency and ability, for example, to communicate. The brain does this by getting rid of redundant pathways or synapses by way of dendritic pruning and continues this remodeling throughout life. Perhaps the most important stages of maturation are during fetal development, early childhood and adolescence. There is individual variation in the maturation process and neuroimaging techniques have enabled the comparison in cortical and sub-cortical changes between different groups of children. A longitudinal neuroimaging study with 45 children aged 5-11 years reported that brain expansion increased by approximately 1 mm per year and predominantly in the frontal cortex. In fact, evidence suggests that the frontal cortex continues to mature well into adulthood and late 20’s (circa: 25-30 years of age). This is in contrast to the limbic system which ignites during puberty and makes the adolescent period a particularly vulnerable time.
Neurons are nerve cells which send electrochemical signals to each other. As a person processes an event, neurons in the brain pass information through synapses (tiny gaps between neurons). This invites surrounding neurons to start firing, creating a network of connections of various strengths. It’s this persistent change in the strength and pattern of connections that is a ‘memory’.
Infantile amnesia, the inability of adults to recollect early episodic memories, is associated with the rapid forgetting that occurs in childhood. It has been suggested that infantile amnesia is due to the underdevelopment of the infant brain, which would preclude memory consolidation, or to deficits in memory retrieval. Although early memories are inaccessible to adults, early-life events, such as neglect or aversive experiences, can greatly impact adult behavior and may predispose individuals to various psychopathologies. It remains unclear how a brain that rapidly forgets, or is not yet able to form long-term memories, can exert such a long-lasting and important influence. Here, with a particular focus on the hippocampal memory system, we review the literature and discuss new evidence obtained in rats that illuminates the paradox of infantile amnesia. We propose that infantile amnesia reflects a developmental critical period during which the learning system is learning how to learn and remember.
