Oct. 23 (UPI) -- New research suggests animals have a relatively accurate sense of time.
Scientists measured activity in the medial entorhinal cortex of a mouse's brain while the rodent performed a task requiring the measurement of a time interval.
"This is one of the most convincing experiments to show that animals really do have an explicit representation of time in their brains," Daniel Dombeck, researcher at Northwestern University, said in a news release.
Because the medial entorhinal cortex, a region of the temporal lobe, facilitates the encoding of spatial information related to episodic memories, Dombeck hypothesized the region helps animals conceptualize time.
"Every memory is a bit different," said James Heys, a postdoctoral fellow in Dombeck's lab. "But there are two central features to all episodic memories: space and time. They always happen in a particular environment and are always structured in time."
In the lab, researchers had mice perform the virtual "door stop" task. The rodents are made to run on a treadmill within a virtual reality environment. The mouse learns to run down a hallway. After 6 seconds elapse, a door at the other end of the hallway opens, allowing the mouse to continue running to retrieve a food reward.
In a followup experiment, the door is made invisible. However, changes in the texture of the floor allowed the test mice to memorize the door's location. In the second experiment, the mice regularly stopped at the location of the invisible door and waited 6 seconds before continuing to run to the food reward.
"The important point here is that the mouse doesn't know when the door is open or closed because it's invisible," said Heys. "The only way he can solve this task efficiently is by using his brain's internal sense of time."
In another test, scientists had mice perform the same task, only this time, researchers used two-photon microscopy to monitor brain activity.
"As the animals run along the track and get to the invisible door, we see the cells firing that control spatial encoding," Dombeck said. "Then, when the animal stops at the door, we see those cells turned off and a new set of cells turn on. This was a big surprise and a new discovery."
The "timing" cells were only active while the test subjects waited at the door.
Researchers think their findings -- published this week in the journal Nature Neuroscience -- explain why household pets are often waiting at the food bowl when it's time for dinner. The research could also help scientists better understand how neurodegenerative diseases disrupt the medial entorhinal cortex.
"Patients with Alzheimer's disease notably forget when things happened in time," Heys said. "Perhaps this is because they are losing some of the basic functions of the entorhinal cortex, which is one of the first brain regions affected by the disease."
Doctors could potentially use time-related memory tasks to identify early signs of Alzheimer's.
"We could start asking people to judge how much time has elapsed or ask them to navigate a virtual reality environment -- essentially having a human do a 'door stop' task," Dombeck said.