Do you ever wonder about your earliest memories? Perhaps the first time you crawled or tasted solid food?
While most of us can’t recall these moments, a recent study conducted by Trinity College Dublin on mice suggests that our brains may still hold onto these memories.
Not only does this research shed light on the enigmatic phenomenon known as infantile amnesia, but it also provides insights into why individuals with autism spectrum disorder (ASD) may have exceptional memory recall.
Are our earliest memories still in our heads?
Infantile amnesia is a pervasive yet often overlooked form of memory loss in humans and mammals, explains neuroscientist Tomás Ryan.
The biological underpinnings behind this amnesia and its impact on the engram cells responsible for encoding each memory remain largely unknown. As a society, we tend to dismiss infant forgetting as an inevitable part of life, paying little attention to it.
Our earliest memories typically begin forming around the ages of two to three years old. However, it is not that our brains are incapable of perceiving the world before this age.
Studies on rats have shown that our brains can indeed create memories and store them as engrams, which are structures that serve as a neurological library. Understanding the mechanisms behind our earliest memories is crucial.
Experiments on rats have shown that infantile amnesia can be prevented using drugs and corticosteroids, suggesting that biochemical processes erode the connections to long-term memories.
Ryan and his team studied how the mother’s immune system affects the environment. They thought that maternal immune activation (MIA), which affects conditions like ASD and schizophrenia, might also affect pathways related to infantile amnesia.
They observed mice trained to fear shocks and found that male offspring of mothers who had immune responses during mid-pregnancy had social behavior issues like those seen in ASD. These male mice also had longer memories of scary events compared to their sisters.
Examining transgenic mice with labeled memory neurons showed differences in the structure and size of memory engrams in the dentate gyrus of the hippocampus.
The presence of a small immune protein, cytokine IL-17a, seemed crucial. Male mice born to mothers lacking this protein did not experience infantile amnesia when similar immune responses occurred during pregnancy.
Although the reasons behind the ‘forget switch’ for some of the earliest memories is still unknown, this study’s mechanisms bring us closer to understanding why some memories persist while others fade away.
Lead researcher Sarah Power emphasizes the impact of early brain development on memory storage and retrieval.
Exploring these mechanisms further could have significant implications for education and medicine, providing a deeper understanding of childhood memories.