Researchers at the Center for Neuroscience at the University of California, Davis have found that commercially available brainwave entrainment devices can stimulate theta brain waves to improve memory performance.

A paper regarding the research has been published in the journal Cognitive Neuroscience.

Brainwave entrainment involves stimulating the brain into entering a specific state through the use of pulsing sound, light or an electromagnetic field. The method aims to encourage a patient’s brain activity to reflect the oscillating patterns of the sensory inputs. Theta brain waves are often targeted because they can be measured outside of the head and are associated with the brain actively monitoring an activity, such as navigating through a maze.

Brainwave entrainment devices are marketed to address numerous issues including anxiety, insomnia, depression and learning difficulties. However, until now there has been very little evidence to support any of these claims.

In a previous study, Professor Charan Ranganath and his colleagues at the Center for Neuroscience found that high levels of theta wave activity immediately before a memory task were associated with a better performance.

This discovery led Brooke Roberts, a postdoctoral researcher in Ranganath’s lab, to test the theory after obtaining a theta brainwave entrainment device. She conducted an experiment which involved 50 volunteers either using the device for 36 minutes or listening to 36 minutes of white noise before undertaking a simple memory test.

Participants who had used the brainwave entrainment device showed both improved memory performance and enhanced theta wave activity.

Roberts then showed her results to Ranganath, who suggested conducting more experiments with new controls. The experiment was repeated with another 40 volunteers, but this time the control group received beta wave stimulations. Beta waves are associated with normal waking consciousness.

Results from the 40-person study also found that theta wave entrainment enhanced theta wave activity and improved memory performance.

Ranganath’s lab also conducted a different study using electrical stimulation to enhance theta waves but this had the opposite effect, as it resulted in disrupted theta wave activity and temporarily weakened memory function.

Ranganath was surprised the devices have worked this well. “What’s surprising is that the device had a lasting effect on theta activity and memory performance for over half an hour after it was switched off,” he said.

There is still an ongoing debate among neuroscientists regarding the function of theta waves but Ranganath now believes that they may play a role in coordinating brain regions. He concluded: “The neurons are more excitable at the peak of the wave, so when the waves of two brain regions are in sync with each other, they can talk to each other.”