We can’t remember much about the first few years of our life, and yet memories do form during that time. Scientists are particularly interested in where they form during these formative years. Now, a new study provides a novel look into this fascinating subject.

Researchers at UC Davis conducted a functional MRI study on 22 sleeping toddlers to work out exactly which areas of the brain are activated when they are in the process of recalling a memory. The research, published in the Proceedings of National Academy of Sciences, shows that the hippocampus is indeed a key region for the development of episodic memory.

The region has already been put forward as fundamental in children, but most research has been done on non-human subjects. This study is the first to show such convincing evidence in children. However, reaching this result has not been easy and required the team to come up with a completely different approach. This is because MRI scans are noisy machines in which the subject needs to be perfectly still while completing a mental task.

Any adult getting an MRI will tell you that it is tiring being in the scanner. Now imagine trying to do an experiment on two-year-olds. But Professor Simona Ghetti and Dr Janani Prabhakar found a great workaround. They came up with a new protocol that allows them to scan the children's hippocampal region when they are sleeping (as opposed to awake, which is typical of other studies).

The new approach had the children listen to a song in the lab while playing with a stuffed toy. At their usual bedtime, the kids went to sleep inside the MRI scan, and while they slept, the researchers either played recordings of the song they had heard previously or an unfamiliar song. The children were then tested when they were awake about which room they had heard the song in or if the song reminded them of the toy they were playing with earlier. The team was specifically interested in episodic memory, which is the ability to link different stimuli together.

The study showed stronger hippocampus activation when a familiar song was played. Not only that but the kids who demonstrated good episodic memory in the awake test also had more activity in the brain scan. The nature of memory remains a complicated matter with many uncertainties, but it is certainly interesting to link childhood memory to the hippocampus.