U. CHICAGO (US) — A good night’s sleep helps the brain retain multiple, potentially conflicting memories, according to new research with starlings.
Other studies have shown that sleep consolidates learning for a new task. The new study, which measured starlings’ ability to recognize new songs, shows that learning a second task can undermine the performance of a previously learned task. But this study shows that sleep helps the brain consolidate learning when two new potentially competing tasks are learned in the same day.
Starlings provide an excellent model for studying memory because of fundamental biological similarities between avian and mammalian brains, scholars write in the paper published in Psychological Science.
“These observations demonstrate that sleep consolidation enhances retention of interfering experiences, facilitating daytime learning and the subsequent formation of stable memories,” the authors write.
For the study, the researchers conducted two experiments using 24 starlings each. They played two recorded songs from other starlings and tested the birds’ ability to recognize and repeat the two songs. After learning to recognize the two songs, the birds were later trained to recognize and perform a different pair of songs.
In their experiments, the authors examined the effect of sleep on the consolidation of starlings’ memories. After learning the second pair of songs, they were tested on the first before they went to sleep. They varied the time between testing.
Researchers found that learning the second pair of songs interfered with the birds’ ability to remember the first pair, regardless of the time between the daytime testing periods. Learning the first pair of songs also interfered with the birds’ ability to remember the second pair when they were tested on the second pair before they went to sleep.
When the starlings were allowed to sleep, however, they showed increases in performance on both the first and second pair of songs, suggesting that sleep consolidation enhances their memory, overcoming the effects of interference.
When taught a new song pair after awaking, the birds were still able to remember what they had learned on the previous day, despite the new interference.
“The study demonstrates that sleep restores performance and makes learning robust against interference encountered after sleep. This process is critical to the formation and stability of long-term memories,” says Howard Nusbaum, professor of psychology at University of Chicago.
Graduate researcher Timothy Brawn and psychology professor Daniel Margoliash are co-authors of the study.
Source: University of Chicago