London, Feb 12 (IANS): Patterns created by the brain's grid cells, which are believed to guide navigation, are modified by the shape of the environment, new research suggests.

This means that grid patterns are not a universal metric for the brain's GPS system to measure distance as previously thought, said the team from the University College London (UCL).

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 are seeing the ruler bending and stretching depending on the geometry of our external environment," explained lead author Julija Krupic from the UCL.

This causes grid patterns to change markedly between enclosures of different shapes and within the same enclosure.

"We were surprised to see how important environmental boundaries are in permanently changing grid patterns and just how local the activity of grid cells is," added co-first author Marius Bauza.

The study that involved rats was published in the journal Nature today.