If sometimes you wonder if your dog is angry with you for staying out late, you might be right. New evidence suggests that animals have a clear sense of time, using previously undiscovered neurons that seem to switch on to count off minutes as they wait. The discovery was made by a team from Northwestern University while studying the medial entorhinal cortex of mice. Located in the mid-temporal lobe, it’s the part of the brain associated with memory and navigation. And since it encodes spatial information in episodic memories, lead study author Daniel Dombeck theorized that it could function as a sort of “inner clock” as well. “There are many similarities between the brains of mice, cats, dogs and humans,” Dombeck told Fox News. “We all have a medial entorhinal cortex (the region we found that may act as an inner clock), so it’s logical to think that this brain region serves a similar function in all of these different species.” To test his theory, Dombeck and his team put a mouse on a physical treadmill in a virtual reality environment. The mouse would run (on the treadmill) down a hallway to a door. After six seconds, the “door” would open and the mouse would get a (non–virtual reality) treat. They would repeat this a few times before making the door invisible. Dombeck was surprised to find that the mouse would still run and stop at the invisible door, waiting for six seconds for it to “open” so it could eat. Since the mouse didn’t know whether the door was open or closed and waited exactly six seconds, the team concluded that it had to have used its inner clock. The researchers also monitored the mouse’s brain activity, finding that the mouse’s neurons would fire as it ran. When it stopped at the door, those neurons would turn off before a new set began firing. These newly discovered neurons only fired when the mouse stopped, keeping track of the time the mouse was resting. Dombeck believes that dogs and cats more than likely have the same neurons that encode time. “There’s evidence that humans and monkeys can estimate time intervals using some form of an ‘inner clock’ and now with our work we know that mice also can explicitly represent time intervals in their brains and can perform timing tasks,” he explained. “Therefore, it’s logical to think that animals in between mice and humans in the hierarchy chain, like our pets (dogs and cats), can also use their brains to estimate time intervals.” The team’s research could have an impact on humans. The entorhinal cortex is one of the first regions of the brain affected by neurodegenerative diseases like Alzheimer’s, and researchers could study how these diseases affect the new time–encoding neurons. “When doing basic research like we are, it’s always difficult to know where or how your findings will make an impact, but it’s really results from basic research like ours that eventually lead to better treatments or understanding of diseases, and sometimes even provide insights into how things like designing better computer software (by mimicking brain function),” Dombeck said. “Since the medial temporal lobe (the larger brain region that includes the medial entorhinal cortex) is one of the first regions affected by Alzheimer’s disease, and since the time keeping properties of this part of the brain were previously unknown, it’s not unreasonable to think that clinicians could soon be asking patients to estimate different amounts of elapsed time as part of the battery of tests to look for early signs of dementia.” The study can be found in the journal Nature Neuroscience.