Shhh! Your baby is learning in sleep too

While infants sleep, they are reprocessing what they have learnt during the day, a study has found.

Working with researchers from the University of Tubingen, scientists from the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany discovered that babies of the age from nine to 16 months remember the names of objects better if they had a short nap.

And only after sleeping can they transfer the learnt names to similar new objects.The infant brain thus forms general categories during sleep, converting experience into knowledge.

The results show that sleep significantly affects memory organisation even in the infant brain - and at a time when memory is growing on a massive scale.

"The waking infant brain quickly forgets newly-learnt names, but during sleep, words are more durably linked to objects and imprinted," said Angela Friederici, director at Max Planck Institute.

The researchers also showed that the formation of categories is closely related to a typical rhythmic activity of the sleeping brain called "sleep spindles".

Infants with high "sleep spindle" activity are particularly good at generalising their experiences and developing new knowledge while sleeping.

In order to study the impact of sleep on infant memory, the team invited parents to attend a study with their nine to 16-month-old children.

During the training session, the infants were repeatedly shown images of certain objects while hearing the fictitious names assigned to the objects.

One group of infants spent the next one to two hours sleeping in their prams while the others remained awake.While the group who had stayed awake had forgotten the names of the individual objects, the children in the sleep group remembered the object-word mappings.

"The infants who slept after the training session assigned new objects to the names of similar-looking objects,"

said Manuela Friedrich of the Max Planck Institute.They were not able to do that before their nap, and nor were the ones who stayed awake able to do it.

"This means that the categories must have been formed during sleep," Friedrich noted.