Sleep facilitates memory consolidation – not just in adults, but also in infants in their first year of life. This has been demonstrated by a team of researchers headed by Dr Sabine Seehagen at the Ruhr-Universität Bochum, for the first time using an experimental design that assesses declarative memories, i.e. memories for facts and events.
The researchers conclude: sleeping after learning appears to be important for infants’ long-term memory. The researchers report their findings in the journal “PNAS“.
Hand puppet test provides insights into declarative memories
In collaboration with a colleague from the University of Sheffield, the Bochum team studied 216 infants aged six and twelve months. The researchers visited each infant twice in his or her home, either immediately after the infant had slept or just before they were expected to fall asleep again following their natural sleeping pattern. During the first visit, the experimenter used a hand puppet to perform specific actions.
During the second visit, the experimenter observed which of those actions were imitated by the infant when he or she saw the puppet again. A third group of infants had not received any demonstrations of the actions before they were allowed to interact with the puppet during the second visit. Thus, the researchers were able to test which actions were performed by the infants spontaneously on seeing the puppet. The intervals between the two visits were either four or 24 hours long.
Only those children who had slept remembered
Infants who slept for at least half an hour without interruption within four hours after the actions were demonstrated reproduced significantly more actions than children in the control group who had not been given any demonstrations.
The results differed for children who had not slept for at least half an hour without interruption within four hours after the first visit. They did not reproduce significantly more actions than children in the control group, i.e. they did not remember the actions the researcher had performed with the puppet. This behaviour occurred after the short as well as after the long interval.