Most people have difficulty accessing detailed memories of their early years of life. This phenomenon is called childhood amnesia and is intrinsically linked to the brain changes that occur during this initial phase of development.
It is important to note that the absence of conscious memories does not imply that babies do not have memory; they acquire knowledge, identify individuals, and retain data from an early age. What is typically lost are explicit recollections of specific events, such as trips, parties, or travels, and this type of record is known as episodic memory.
The hippocampus is one of the brain regions involved in the memorization process, assisting both in the recording and retrieval of experiences and occurrences. One of the theories studied to explain childhood amnesia involves neurogenesis, which is the process of creating new neurons.
In 2012, Sheena A. Josselyn and Paul W. Frankland proposed a hypothesis, detailed in an article in the journal Learning & Memory, suggesting that the high rate of new neuron production in the hippocampus during the first years of life could interfere with the retention of certain memories.
This idea gained more support after experiments conducted in 2014 by researchers at The Hospital for Sick Children, located in Toronto. The study, published in the journal Science, demonstrated a correlation between the greater generation of new neurons and a faster forgetting of certain memories in young animals.
Scientists also noted that reducing the formation of new neurons after forming a memory decreased forgetting in some scenarios. A possible justification for this is that this intense renewal alters brain connections, making it difficult to maintain certain memories.
However, childhood amnesia appears to be multifactorial. In addition to changes in the hippocampus and neurogenesis, the development of other brain areas and the acquisition of new skills during childhood can also affect how early experiences are stored and accessed.
The difficulty in recalling the early years does not mean that all the experience of that period is lost, given that there are various modalities of memory. While episodic memory allows conscious recall of specific facts, including the temporal and spatial context, it is autobiographical memories that present this initial gap.
Implicit memories, on the other hand, are linked to learning that shapes behavior without a conscious recollection of when the learning occurred.