When navigating a space, human brains turn out to form eerily similar brainwaves with spatial awareness. Scientists discovered this after devising a method to scan our brains during free movements, instead of lying still in a scanner.
“Our results imply that our brains create a universal signature to put ourselves in other people’s shoes,” explains neurosurgeon Nanthia Suthana of the University of California, Los Angeles.
Previous studies in rats showed that low-frequency brainwaves help rodents keep track of their position as they explore a new place – by defining the boundaries of a place. Similar boundary-defining waves had also been observed in humans, but only when navigating a virtual environment while remaining still for brain scans.
“We wanted to investigate this idea in humans – and test whether they could track others in their environment – but we were hampered by existing technology,” said UCLA neuroscientist Matthias Stangl.
So Stangl and colleagues created a mobile brain scanner, consisting 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 brain forms and evoke spatial memories.
The wireless recording device. (Suthana lab / UCLA)
Their subjects were five epilepsy patients who already had electrodes implanted in their brains to control their seizures. These implants lie in the medial-temporal lobe – our brain bits are believed to code for long-lasting, deliberate 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 in a room. This was followed by a 15-minute observation task where their participants had to follow if someone else was navigating the room, and press a button when the other person passed the unmarked target locations.
The researchers saw that as participants approached a physical boundary – like the wall of a room – the flow of low-frequency oscillations in their brains increased in strength. The same happened when they saw someone else approaching the walls.
“We found that boundary-related oscillatory changes were remarkably similar between tasks requiring self-navigation versus observation of another person,” they wrote in their paper.
Recent studies in rats and bats have also found that 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 brainwave representations of a space, shown 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, only their strength.
(Suthana lab / UCLA)
Above: Visualized brainwave strength map of the boundaries of the room, with red representing greater amounts of power in brainwave signals.
“Our results support the idea that, under certain mental states, this brain wave pattern can help us recognize boundaries,” said Stangl. “In this case, it was when people were focused on a target and were hunting for something.”
The electrical activity being measured oscillates within a frequency range called theta waves. We generally produce these slow but pronounced waves while navigating, so it is not surprising that they are clearly visible in such a task.
Interestingly, slightly more humming 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, record experiences in our working memory.
The team believes that the brainwaves they observed are generated by multiple groups of neurons, which may include cells that specifically code for boundaries, objects, and other boundaries and target objects. A better understanding of this neuronal language can 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 is published in Nature.