Rats and bats brains work differently on the move

Scientists have found significant differences between the rhythms in a part of the brain used in navigation in rats and bats.The study challenges a widely used model - based on studies in rodents of how animals navigate their environment.

To get a clearer picture of the processes at work in the mammal brain during spatial navigation, neuroscientists must closely study a broad range of animals, said scientists from the University of Maryland.

Along with colleagues from Boston University, the researchers focused on specialised cells that process spatial information in a region called the medial entorhinal cortex, a hub of neural networks for memory and navigation.

Earlier experiments showed rats' brain cells in this area fire continuously in a rhythmic electrical signal called a theta wave when the animals are navigating through space. Some models of the brain treat theta waves as a key element of spatial navigation in all mammals, but this idea is based on rodent research, UMD researcher Cynthia Moss said.

The team tested for rhythmic electrical responses at the cellular level in bat and rat brain tissue. They found evidence for theta waves in the rat cells. But in the bat cells these waves were absent, said Moss, who has studied bats since the 1980s.

"This raises questions as to whether theta rhythms are actually doing what the spatial navigation theory proposes," said co-author, UMD biology researcher Katrina Mac Leod. "To understand brains, including ours, we really must study neural activity in a variety of animals," Mac Leod said.

Humans and other mammals share many common features of brain organisation, and the differences in theta waves between bats and rats raises questions about how spatial information is represented in all brains, researchers said The study was published in journal Science.