Using direct human brain
recordings, a research team from Drexel University, the University of
Pennsylvania, UCLA and Thomas Jefferson University has identified a new type of
cell in the brain that helps people to keep track of their relative location while
navigating an unfamiliar environment. The grid cell, which derives its name
from the triangular grid pattern in which the cell activates during navigation,
is distinct among brain cells because its activation represents multiple
spatial locations. This behavior is how grid cells allow the brain to keep
track of navigational cues such as how far you are from a starting point or
your last turn. This type of navigation is called path integration. It is
critical that this grid pattern is so consistent because it shows how people
can keep track of their location even in new environments with inconsistent
layouts researchers mentioned in Drexel's School of Biomedical Engineering,
Science and Health Systems. Researchers were able to discern these cells because
they had the rare opportunity to study brain recordings of epilepsy patients
with electrodes implanted deep inside their brains as part of their treatment.
Their work is being published in the latest edition of Nature Neuroscience.
During brain recording, the 14
study participants played a video game that challenged them to navigate from
one point to another to retrieve objects and then recall how to get back to the
places where each object was located. The participants used a joystick to ride
a virtual bicycle across a wide-open terrain displayed on a laptop by their
hospital beds. After participants made trial runs where each of the objects was
visible in the distance, they were put back at the center of the map and the
objects were made invisible until the bicycle was right in front of them. The
researchers then asked the participants to travel to particular objects in
different sequences. The team studied the relation between how the participants
navigated in the video game and the activity of individual neurons. Each grid
cell responds at multiple spatial locations that are arranged in the shape of a
grid. This triangular grid pattern thus appears to be a brain pattern that
plays a fundamental role in navigation. Without grid cells, it is likely that
humans would frequently get lost or have to navigate based only on landmarks.
Grid cells are thus critical for maintaining a sense of location in an
environment.
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