Deer Mouse

Though animals probably cannot relate to abstract human concepts such as minutes and hours, there is plenty of evidence that they can sense the passing of time. In one study, cats trained to go to different bowls for food when released from confinement based on how long they had been in the cage were able to differentiate 5-second and 8-second intervals.

A recent study of mice may offer a new understanding of how mammalian brains keep track of such short intervals of time. (Though all species of mammals are different, the similarities between us are immense, including the ways in which our brains and the rest of our nervous systems function.)

Mice were trained to run on a real treadmill in a virtual reality set-up. Halfway down a hallway scene, where the apparent texture of the floor changes, there is a door. The mice stop at the sight of the door, but after 6 seconds, the door opens and they resume running down the hallway to collect a food reward. In the test condition, the door is invisible, but its location is detectable because of the change in the flooring.

Even when the door is invisible to the mice, they pause for 6 seconds and then resume running along the hallway to the food reward. Using virtual reality eliminated all possible sensory cues for the mice. Unable to perceive a door, the mice based their behavior on their brain’s internal sense of time.

The scientists used an advanced technique to see the mice brains in high-resolution and observed the neurons firing in the brain. While mice were running, the neurons involved in spatial tasks were firing. When the mice stopped, those cells ceased to be active and a new group of cells that had not been firing became active. Those cells apparently encode how much time the mouse has been engaged in resting behavior.

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These previously unknown neurons are in the medial entorhinal cortex of the brain, and they turn on and keep track of time when an animal is waiting for something. The research shows that mice have a physical representation of time in their brain that allows them to measure a time interval.

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It's advantageous to anticipate the appearance of food that becomes available according to predictable temporal patterns. One example of this occurs in Eurasian Oystercatchers, a bird species that reliably heads to the mudflats along the shore to feed on marine invertebrates during low tide. Researchers documented the daily low tides and the median time that birds departed the roost and flew to the shore.

Compared to the optimal time, birds were early to the mudflats on days when the low tide came late and they were late on the days that the low tide arrived early. Researchers concluded that the birds are able to keep track of time with some mechanism that is not directly associated with the tide.

The increasing attention to animals’ ability to track it suggests that biologists think time is relatively compelling.

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Karen B. London, Ph.D. is a Certified Applied Animal Behaviorist, Certified Professional Dog Trainer, author, and an Adjunct Faculty in NAU’s Department of Biological Sciences.


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