Have you ever seen a rat scurry through an alley and wondered “what is that little guy thinking?”
Research published this week in the Science journal indicated that these rodents have imaginations and can think about more abstract things than humans might realize.
Work on this research began nearly a decade ago when Chongxi Lai, a postdoc in the Harris and Lee Labs and first author of a paper, arrived at the Janelia Research Campus at Howard Hughes Medical Institute.
“A team from the Lee and Harris labs developed a novel system combining virtual reality and a brain-machine interface to probe the rat’s inner thoughts,” said a press release regarding the research. “They found that, like humans, animals can think about places and objects that aren’t right in front of them, using their thoughts to imagine walking to a location or moving a remote object to a specific spot.”
They reached this conclusion based on neural activity patterns activated in the hippocampus – an area of the brain that controls spatial memory – when rats experience places and events. Rats can “voluntarily generate these same activity patterns and do so to recall remote locations distant from their current position,” said the release.
An ability to recall locations away from one’s current position is an important part of memory as well as imagining future scenarios.
“To imagine is one of the remarkable things that humans can do. Now we have found that animals can do it too, and we found a way to study it,” explained Albert Lee, formerly a Group Leader at Janelia and now an HHMI Investigator at Beth Israel Deaconess Medical Center.
Lai and Lee were introduced by Janelia Senior Fellow Tim Harris shortly after Li’s arrival and they soon developed a system that allowed them to understand what animals were thinking by measuring neural activity. The press release described it as a “real time thought detector.”
To create this thought detector, they used a brain-machine interface (BMI) to provide a direct connection between “electrical activity in the rat’s hippocampus and its position in a 360-degree virtual reality arena.” They also created a “thought dictionary” to decode rat brain signals.
“The rat is harnessed in the VR system, designed by Shinsuke Tanaka, a postdoc in the Lee Lab. As the rat walks on a spherical treadmill, its movements are translated on the 360-degree screen. The rat is rewarded when it navigates to its goal,” said the press release.
As this is happening, the BMI records hippocampal activity and the researchers can observe which neurons are activated when rats navigate to their goal. That activity is then translated to actions on a screen.
“Next, the researchers disconnect the treadmill and reward the rat for reproducing the hippocampal activity pattern associated with a goal location,” the press release explained. “In this ‘Jumper’ task – named after a 2008 movie of the same name – the BMI translates the animal’s brain activity into motion on the virtual reality screen.”
From “Jumper” to a galaxy far, far, away, the rats are then guided to perform the “Jedi” task, or imagining moving an object to a location by controlling its hippocampal activity. That would be equivalent of a human imagining walking into their living room with a cup of tea when they are actually sitting in their kitchen. Overall, they found that rats can control their hippocampal activity much like humans do. Rats were also able to hold their thoughts for many seconds.
“The stunning thing is how rats learn to think about that place, and no other place, for a very long period of time, based on our, perhaps naïve, notion of the attention span of a rat,” Harris said.
Going forward, the system described in the study can be used to further study hippocampal activity.