Implanted electrode. (Suthana lab/UCLA) HEALTH How Our Brains Track Other People's Location Is Weirdly Consistent Between Brains TESSA KOUMOUNDOUROS 24 DECEMBER 2020
When navigating a space, it turns out human brains form eerily similar spatial-awareness brain waves. Scientists have discovered this after devising a method to scan our brains during free movements, as opposed to lying still in a scanner.
"Our results imply that our brains create a universal signature to put ourselves in someone else's shoes," explained neurosurgeon Nanthia Suthana from the University of California, Los Angeles.
Previous studies in rats revealed low-frequency brain waves help rodents keep track of their position when exploring a new place – by defining a place's boundaries. Similar boundary-defining waves had also been identified in humans, but only when they navigated a virtual environment while they remained still for brain scans.
"We wanted to investigate this idea in people – and test whether they could also monitor others near them – but were hampered by existing technology," said neuroscientist Matthias Stangl from UCLA.
So Stangl and colleagues created a mobile brain scanner, composed of a backpack with a computer that wirelessly connects to electrodes implanted in the brain (a system called intracranial electroencephalography) to help them study how our brains form and recall spatial memories.
The wireless recording device. (Suthana lab/UCLA)
Their subjects were five epilepsy patients who already had electrodes implanted in their brains to help control their seizures. These implants lie in the medial-temporal lobe – our brain bits thought to encode long-term, intentional memories, and spatial cognition.
Participants took part in a 15-minute navigation task where they were asked to find and learn the locations of hidden targets within a room. This was followed by a 15-minute observation task where their participants had to keep track of someone else navigating the room, and press a button when the other person crossed the unmarked target locations.
The researchers saw that as participants approached a physical boundary – such as the wall of a room – the flow of low-frequency oscillations in their brain increased in power. The same happened when they watched someone else approach the walls.
"We found that boundary-related oscillatory changes were strikingly similar between tasks that required self-navigation versus observation of another person," they wrote in their paper.
Recent studies in rats and bats also found the same group of hippocampal neurons code for both the animal's own location and the location of others of their species.
The power of these brain wave representations of a space, visualised below, also increased when participants were focused on finding their target location. The oscillation signals were not continuous, and did not change the amount they occurred, just their strength.
Above: Visualised brainwave strength map of the room's boundaries with red representing greater amounts of power in brainwave signals.
"Our results support the idea that, under certain mental states, this pattern of brain waves may help us recognize boundaries," said Stangl. "In this case, it was when people were focused on a goal and hunting for something."
The electrical activity being measured oscillated within a frequency range referred to as theta waves. We generally produce these slow but pronounced waves while navigating, so it's hardly surprising to have them evident in such a task.
Interestingly, somewhat more buzzy gamma waves also appeared in similar patterns, with a little more variation between different conditions. These are the waves we produce when we use more of our brains to think, drawing experiences into our working memory.
The team believes the brainwaves they observed are generated by multiple groups of neurons that may include cells that encode specifically for borders, objects, and other boundaries and goal objects. Better understanding this neuronal language may help us unravel brain disorders.
And, in an exciting development, they have made their backpack design available to other researchers. Soon, we can expect to learn even more about our brainwave patterns in complex social situations.
Their research was published in Nature.