If you’re not willing to send electrical shocks through your brain – “mild” as they might be – to become smarter, here’s a much gentler option: play sounds while you sleep. Researchers have found that “carefully timed” sounds, like the rise and fall of waves washing against the shore, can help people remember things that they learned the previous day.
In the human brain a network of neurons are often activated together. The collective rise and fall of activity of the network produces oscillations, the lines we see in an EEG. At different times the brain oscillates at different frequencies. During sleep the brain produces slow, <1 Hz oscillations – hence the term “slow-wave sleep” – and these oscillations are thought to be important for consolidating memories. The idea that the scientists at the University of Tübingen in Germany wanted to test was whether or not auditory stimulation that boosted the slow-wave oscillations also boosted memory.
The study included 11 people who learned word associations right before they went to bed. Their word assocaition memory was tested before they went to sleep and then again the following day. While they slept, they were played short durations of pink noise, a hissing sound similar to white noise. Importantly, the pink noise sounds were timed to the sleeping person’s “slow-wave” brain oscillations. When the individuals received the pink noise stimulation they were able to remember twice as many word associations than without the stimulation. When they repeated the experiment with pink noise that was not synchronized to the slow-waves, they saw no improvement in memory.