Researchers in the US have developed a wireless device that can record the brain activity of mice while moving in their natural habitats, allowing the study of complex behaviours that cannot be studied in the lab. 

Researchers from Cornell University, New York, put together modules to record brain activity and modify it by shining light on groups of neurones genetically altered to be activated by light, and to log animal activities such as locomotion, vocalisations and eye movements. The surgically implanted hat-shaped device, which is small and light, can record continuously from 3 to 9 hours, depending on battery size, or longer if set to save battery when animals are inactive.  

"Before you could either record neural activity with high resolution in the lab or you could record behavior in nature—now we can do both," said Azahara Oliva, co-leader of the study published in Nature Methods. 

To test the device, the team recorded the brain activity of a group of mice kept for two weeks in an outdoor large enclosed field mimicking their naturalistic environment, to understand how their brains navigate the surroundings. They recorded the activity of “place cells” — neurones that become active when an animal enters specific locations. “We’re seeing that the cells have to some degree shared properties to the ones that have been observed in the lab, but to a large extent have many differences that we’re further investigating in follow-up studies,” said co-leader Antonio Fernandez-Ruiz, also from Cornell. 

Future research includes adding modules to measure additional data and studying the coordination of mouse groups while performing complex tasks, social dynamics, the effects of seasonal changes and of psychedelics in the brain. Collaborators are already using the device to study other animals, namely birds, bats and monkeys.