NEW YORK — Scientists have discovered a brain cell that boosts memory and navigation skills. It offers hope of new treatments for neurodegenerative diseases, including Alzheimer’s.
The neuron was identified during virtual reality experiments. It helps center people within their “mental maps.”
“In humans, it is only rarely possible to directly record the activity of single neurons from the brain, due to ethical reasons,” says the study’s first author Dr. Lukas Kunz, a postdoctoral research scientist at Columbia University’s Department of Biomedical Engineering, in a statement.
Brain scans like magnetic resonance imaging (MRI) or electroencephalography (EEG) enable indirect measurements. “But this type of neural activity reflects the sum activity of millions of neurons, which does not allow for direct conclusions about the working principles of single neurons,” Dr. Kunz adds.
In the study, 15 epilepsy patients were implanted with electrodes to help the researchers monitor their disorder. The German volunteers were asked to perform navigation tests on a computer and remember the location of different objects. At the same time, the activity of more than 1,400 single neurons in multiple brain regions was recorded in each individual. Over 160 neurons behaved like “egocentric spatial cell types,” which center on the self. They’ve only been found in rats before.
“We are now the first to report egocentric spatial cell types in humans,” says Dr. Kunz. The study suggests they encode spatial information on a “mental map” centered in each person.
“This is presumably important for everyday life, when humans try to orient themselves in their environments and when they navigate along routes,” says senior author Joshua Jacobs, an associate professor of biomedical engineering. The cell types were particularly abundant in the parahippocampal cortex, a region deep within the brain. They comprised about a quarter of all the neurons.
“Previous studies had shown patients with damage to this brain region are disoriented, presumably because their egocentric bearing cells were affected,” adds Dr. Kunz. The cells also showed increases in activity when the patients used their memory to successfully recall the locations of objects they had found in the virtual environments.
“This suggests these cells are not only relevant for navigation, but also play a role in correctly remembering past experiences. Memories consist of multiple different elements, such as a specific event, the place where the event happened, and the time when the event happened,” notes Dr. Kunz. “We believe that there are different neural systems for the different components of these memories. Egocentric bearing cells are presumably particularly involved in processing the spatial information of the memories.”
Brain discovery could shed light on cognitive struggles seen in people with neurological disorders
The findings illuminate what might go wrong in people with memory problems, such as dementia sufferers. “Their egocentric bearing cells may not function correctly, or may have been destroyed for some reason, such as a stroke, a brain tumor, or dementia,” says Prof Jacobs.
There are two strategies humans and animals use to navigate: allocentric or egocentric frames of reference rooted in the external or internal world. Whenever you use a mobile phone app to find driving directions, it will likely employ both these modes of navigation. When you first type in an address, your app will normally show you the address on a map from an allocentric perspective, with north at the top and south at the bottom. When you then go to route view, it will switch to an egocentric perspective where “ahead” is at the top and “behind” is at the bottom.
In the future, the researchers want to see why exactly any given egocentric bearing cell is tuned to whatever point in space it is focused on. Dr. Kunz and colleagues assume multiple different spatial cues, such as objects, spatial boundaries, and landmarks, combine to influence the position of these reference points. Scientists can examine the influence these cues have on the location of these reference points by removing these cues from environments during experiments.
“Another important question is how egocentric bearing cells interact with allocentric spatial cell types,” says Dr. Kunz. “We currently hypothesize that egocentric bearing cells provide essential input to allocentric spatial cell types. By understanding this, future studies could explain how the tuning of allocentric spatial cell types is influenced by the functioning of egocentric bearing cells.”
This study is published in Neuron.
SWNS writer Mark Waghorn contributed to this report.