Smart rats show human-like powers of imagination in neural research

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Rats can imagine places they are not in and objects they cannot see, according to research that suggests the smart rodents evoked in Hollywood films such as Ratatouille may be less fanciful than they appear.  

Virtual reality analysis of the mammals’ brain activity showed they developed the ideas of going to previously visited locations and moving items they recognised from one area to another, says the paper published by Science on Thursday.  

The work by experts at the Howard Hughes Medical Institute in the US reveals animals’ mental sophistication and promises to boost development in the fast-growing medical field of neuroprosthesis, or using brain functions to control devices such as artificial limbs, robotic arms or hearing implants. 

“To imagine is one of the remarkable things that humans can do,” said Albert Lee, one of the paper’s authors. “Now we have found that animals can do it too.”

The work used experiments devised by lead author Chongxi Lai and others to focus on the hippocampus, the area of the brain linked to spatial memory, imagination and learning. 

Researchers used a so-called brain-machine interface to measure hippocampus electrical activity as the rats journeyed on a spherical treadmill towards a reward. The team then disconnected the treadmill to see if the rodents would repeat the previously observed brain patterns while remaining stationary themselves. 

One test — dubbed Jumper after a 2008 film that featured a teleporting main character — linked the rats to a virtual reality screen to show them thinking about how they would navigate towards their goals.

A second test — called Jedi after the mind-controlling knights of the Star Wars movies — investigated brain patterns that corresponded to the rodents imagining moving an object not in view.  

The aspirational rats were capable of imagining the actions needed to achieve their aims, the researchers found. The rodents proved capable of fixing their thoughts on a given location for several seconds in much the same way humans do when they recall a previous experience or imagine a future event. 

The findings about hippocampus activity offer clues to the “richness of our inner lives”, wrote the researchers at the Maryland-based HHMI.  

The rat research represents an “exciting expansion” in uses of brain-machine interfaces, according to the University of California’s Michael Coulter and Caleb Kemere of Rice University in Texas, who were not involved in the research. In a commentary published separately in Science, they said the experiments provided a new tool for probing “circuit-level mechanisms of mental navigation and spatial imagination”. 

While the rat subjects’ imaginative powers might be less sophisticated than those of Ratatouille’s rodent hero as he vies to become a top Paris chef, the findings will help develop practical applications related to the human mind.

“I haven’t seen Ratatouille, but having worked with rats for a long time they do look like they are focusing and thinking,” said Lee. “They are quite complex — and they have mostly the same brain areas that humans have.”