The word imagination has different meanings. If we refer, specifically, to the meaning that refers to the capacity, faculty or action of forming new ideas, mental images or concepts of external objects, situations or actions that are not present, we can believe that it is such an important human capacity as necessary.
But the "human" attribute falls short. We are not the only species with this faculty that the dictionary of the Royal Spanish Academy attributes to the "soul." Rats also have imagination, according to a study led by experts from the Janelia Research Campus of the Howard Hughes Medical Institute (Maryland, United States), whose results have been published (November 2) in the journal Science.
The authors of the new study have developed a novel system that combines virtual reality and a brain-machine interface to probe the internal thoughts of rats (from the laboratory specimens used in this research). This new system has now been tested with rats but it is not ruled out that it provides similar results with other species of higher animals. Previous scientific studies, based on different analysis methods, have pointed out that various species of apes and cetaceans, for example, show activities that seem to respond to this capacity that we call imagination.
The first major conclusion of the study that is now published, as summarized by the Howard Hughes Institute, is that, like humans, these laboratory rodents can think about places and objects that are not right in front of them, for which they use their thoughts to imagine walking to a place or moving a remote object to a specific location."
"Like humans, when rodents experience places and events, specific patterns of neural activity are activated in the hippocampus, an area of the brain responsible for spatial memory. The new study finds that rats can voluntarily generate these same patterns of activity and do so to remember remote locations distant from its current position. In fact, the rat can activate the representation of places in the environment without having to go there," says Chongxi Lai, a postdoc in the Harris and Lee laboratories and first author of a article in which the results of the study are presented.
This ability to imagine places far from the current position is essential for remembering past events and imagining possible future scenarios. Therefore, the new work shows that animals, like humans, have a form of imagination, according to the study's authors.
“Imagining is one of the most extraordinary things we humans can do. Now we've discovered that animals can do it too, and we found a way to study it,” says Albert Lee, former group leader at Janelia and now an HHMI investigator at Beth Israel Deaconess Medical Center.
The project began nine years ago when Chongxi Lai arrived at the Janelia campus as a graduate student with the idea of testing whether an animal could think. Her advisor, Tim Harris, a senior fellow at Janelia, suggested Lai walk down the hall to chat with Lee, whose lab had similar projects underway.
Together, the labs worked to develop a system to understand what animals think: a real-time "thought detector" that could measure neural activity and translate what it means.
The system uses a brain-machine interface (BMI), which provides a direct connection between brain activity and an external device. In the team's system, BMI produces a connection between electrical activity in the rat's hippocampus and its position in a 360-degree virtual reality field.
The hippocampus stores mental maps of the world involved in remembering past events and imagining future scenarios. Memory recall involves the generation of specific hippocampal activity patterns related to places and events. But no one knew if animals could voluntarily control this activity.
BMI allows researchers to test whether a rat can activate hippocampal activity just by thinking about a location in the arena without physically going there; Essentially, it detects whether the animal is able to imagine going to that place.
Once their system was developed, the researchers had to create the “thinking dictionary” that would allow them to decode the rat's brain signals. This dictionary compiles what activity patterns look like when the rat experiences something (in this case, places in the realm of virtual reality).
The rat is hooked to the virtual reality system, designed by Shinsuke Tanaka, a postdoc at the Lee Lab. As the rat walks on a spherical treadmill, its movements are translated onto the 360-degree screen. The rat is rewarded when it navigates towards its target.
At the same time, the BMI system records the activity of the rat's hippocampus. The researchers can see which neurons fire as the rat navigates the arena to reach each target. These signals provide the basis for real-time hippocampal BMI, with the brain's hippocampal activity translated into actions on the screen.
Next, the researchers unplug the treadmill and reward the rat for reproducing the pattern of hippocampal activity associated with the location of a target. In this "Jumper" task, named after a 2008 film of the same name, the BMI translates the animal's brain activity into motion on the virtual reality screen. Essentially, the animal uses its thoughts to navigate toward the reward by first thinking about where it needs to go to get the reward. This thought process is something we humans experience regularly. For example, when we are asked to go buy food at a store we know, we can imagine the places we will pass along the way before leaving home.
In the second task, the "Jedi" task, named after Star Wars, the rat moves an object to a location solely with its thoughts. The rat is fixed in a virtual location but "moves" an object to a goal in virtual reality space by controlling its hippocampal activity, in the same way that a person sitting in their office might imagine sipping a cup next to the machine. of coffee and filling it with coffee. The researchers then changed the target location, requiring the animal to produce activity patterns associated with the new location.
The team found that rats can precisely and flexibly control the activity of their hippocampus, in the same way that humans probably do. Animals are also able to maintain this hippocampal activity, holding their thoughts in a given location for many seconds, a similar period of time as humans relive past events or imagine new scenarios.
"What's amazing is how rats learn to think in that place, and nowhere else, for a very long period of time, based on our perhaps naïve notion of a rat's attention span," Harris says.
The research also shows that BMI can be used to probe hippocampal activity, providing a novel system to study this important brain region. As BMI is increasingly used in prosthetics, this new work also opens up the possibility of designing new prosthetic devices based on the same principles, according to the authors.
