Researchers have witnessed a new phenomenon in the brain as humans start to store new memories – literally brain waves.
New research has found that a travelling wave tends to move from the back to the front of the brain while people start to put something in their memory, and it’s then reversed when they recall the information.
A paper, published in the journal Nature Human Behaviour, sheds new light on the how the brain coordinates its many regions and billions of neurons.
“Broadly, we found that waves tended to move from the back of the brain to the front while patients were putting something into their memory,” says co-author Uma R. Mohan, a postdoctoral researcher at the National Institutes of Health in the US.
“When patients were later searching to recall the same information, those waves moved in the opposite direction, from the front towards the back of the brain.”
Brain waves are electrical oscillations that represent patterns of neural activity. Travelling waves spread out across the cerebral cortex – the outermost layer that supports higher cognitive processing – not unlike ripples on a pond.
“We’re looking at neural oscillations not as independent stationary things but as things that are constantly and spontaneously moving across the brain in a dynamic way,” Mohan says.
This way of understanding brain waves offers a pathway to explaining how the brain quickly coordinates activity and shares information across multiple regions.
The participants enrolled in this study were being treated for drug-resistant epilepsy, with electrodes temporarily implanted on the surface of the brain to determine where their seizures arise.
“It’s a rare opportunity to be able to see what’s going on directly from the brain while the participants are engaged in different cognitive behaviours,” Mohan said.
Researchers recorded the participants’ brain activity while they performed tasks that required memorising and recalling lists of words or letters.
“I implemented a method to label waves traveling in one direction as basically ‘good for putting something into memory.’ Then we could see how the direction switched over the course of the task,” says Mohan.
“The waves tended to go in the participant’s encoding direction when that participant was putting something into memory and in the opposite direction right before they recalled the word,” she says.
“Overall, this new work links traveling waves to behaviour by demonstrating that traveling waves propagate in different directions across the cortex for separate memory processes.”
