Why don’t we remember just things about our childhood although it is the period in which we learn things? Until now it was thought that we do not retain these experiences because the part of the brain responsible for keeping memories, the hippocampus, is still developing and does not reach its maximum development until well into adolescence and, therefore, it cannot encode memories in our early years. However, a new investigation carried out in the Yale University (USA) Find evidence that this is not so.
Posted in magazine ‘Science‘, The study tried to find out what happens in the brain of babies showing them images to later check if they remembered them. According to the researchers, when a baby’s hippocampus was more active to see an image for the first time, it was more likely to recognize it later.
The findings indicate that memories can effectively codify in our brain during the first years of life. Now scientists are studying what happens with those memories over time.
Our inability to remember specific events of the first years of life is called «Child Amnesia». However, studying this phenomenon is a challenge.
“The distinctive seal of this type of memories, which we call episodic memories, is that you can describe them to others, but that is not possible when it comes to preverbal babies,” he explains Nick Turk-Brownedirector of the WU TSAI Institute of YALE and main author of the study.
The team, led by Tristan Yates, postdoctoral researcher in the Columbia Universityused a method that consisted of showing babies between four months and two years the image of a new face, object or scene.
Subsequently, after the babies saw several more images, the researchers showed them an image previously seen next to a new one.
“When babies have only seen something once, we hope they look at him more attention to see him again,” Turk-Browne said. Therefore, in this task, if a baby stares at the previous image more than the new one next to it, it can be interpreted as recognizing it as a relative ».
The team, a pioneer in methods to make images by functional magnetic resonance (FMRI) with awake babies (which has historically been difficult due to the short attention of babies and their inability to stay still or follow instructions), evaluated the activity in the baby’s hippocampus while seeing the images.
Specifically, they evaluated whether the hippocampal activity was related to the strength of a baby’s memories. They discovered that the greater the activity in the hippocampus when a baby watched a new image, the longer he looked at her when she reappeared later.
Behind the neck
The back of the hippocampus (the closer to the neck), where the coding activity was more intense, is the same area that is mainly associated with the Episodic memory In adults.
These findings were seen in the 26 babies analyzed, but were more forceful among those over 12 months.
Previously, the team discovered that the hippocampus of babies of only three months showed a different type of memory called ‘Statistical learning‘.
Episodic memory refers to remembering specific events, such as dinner with friends, while statistical learning focuses on identifying patterns between events, such as the aspect of restaurants or the location of these.
Episodic memory and statistical learning use different neuronal pathways in the hippocampus. Previous studies in animals show that the statistical learning route, located in the anterior part of the hippocampus, develops before the episodic memory. Turk-Browne suggests that episodic memory could appear later in childhood, around the year, considering the needs of babies.
«Statistical learning consists in extracting the structure of the world around us, he says. This is crucial for language development, vision, concepts and more. Therefore, it is understandable that statistical learning can come into play before episodic memory ».
Even so, this work shows that the hippocampus can encode episodic memories before what was believed, long before the first memories that we can record in adulthood. So,What happens to these memories?
There are several possibilities, says Turk-Browne.
One is that memories do not store long term and, therefore, they simply do not last long. Another is that memories persist long after coding and we simply cannot access them. Turk-Browne suspects that it could be the latter.
In an ongoing work, Turk-Browne’s team is testing if babies, young children and children can remember home videos taken from their perspective when they were babies (smaller), and tentative pilot results show that these memories could persist until preschool age before fading.
The new findings, directed by Yates, provide an important connection.
“Tristan’s work in humans is compatible with recent evidence in animals that indicates that child amnesia is a recovery problem,” says Turk-Browne. We are working to trace the persistence of hippocampal memories throughout childhood and we are even beginning to consider the radical possibility, almost of Science fictionthat they can last in some way in adulthood, despite being inaccessible ».
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