Brain's GPS system influenced by shape of environment

Patterns created by the brain's grid cells, which are believed to guide navigation, are modified by the shape of the environment, according to new research.
This means grid patterns are not a universal metric for the brain's GPS system to measure distance, as previously thought, researchers said.
Grid cells in the brain appear to form an internal map of the local environment by signalling periodically to create a 'grid-pattern' that helps animals to navigate, even in the dark.
Until now, it was believed that all grid patterns were hexagonal, providing the brain with uniformly spaced regions across which distances could be measured.

The new research dispels this theory as it shows grid patterns distort to align with the local environment's geometry, changing the distances between grid-regions.
"If you imagine the pattern made by grid cells is a ruler for our brains to measure distance, we're seeing the ruler bending and stretching depending on the geometry of our external environment," said leading author Dr Julija Krupic from the University College London.

"This causes grid patterns to change markedly between enclosures of different shapes and within the same enclosure," said Krupic.
The study in rats shows that the structure of the grid pattern is responsive to environmental shape to such an extent that highly polarised trapezoid-shaped environments cause the usual hexagonal grid pattern to break as the grid aligns to the enclosure walls.

The scientists studied the grid patterns created in the entorhinal cortex part of the brain of 41 rats as they foraged in circular, square or trapezoid shaped environments.
They found grid patterns aligned at an angle of 8.8 degrees to the walls in polarised enclosures and discovered that this influence was strong enough to cause distortions in trapezoid shaped spaces.
The study was published in the journal Nature.