Ever wonder if your pet notices when you're late for feeding time? New research from Northwestern University provides compelling evidence that animals can indeed judge time intervals. Scientists identified a novel set of neurons in the medial entorhinal cortex that activate like an internal clock while animals wait.
"Does your dog know it took you twice as long today to feed him? Previously, we lacked a clear answer," says Daniel Dombeck, PhD, lead researcher. "This study offers one of the strongest demonstrations that animals possess an explicit neural representation of time during interval timing tasks."
Dombeck's team targeted the medial entorhinal cortex, a brain region linked to memory and navigation. Known for encoding spatial data in episodic memories, this area likely handles temporal information too.
"Every episodic memory combines space and time—occurring in a specific place at a precise moment," explains James Heys, PhD, postdoctoral fellow and lead author.
In their virtual 'doorstop' task, mice ran on a treadmill in a VR hallway. They learned to stop at a virtual door halfway down, waiting six seconds for it to open and access a reward.
Researchers then made the door invisible. Mice still paused precisely at the spot, using floor textures as cues, and waited exactly six seconds before dashing to the reward.
"With the door invisible, the mouse can't rely on visual cues," Heys notes. "It must tap into its internal sense of time to succeed efficiently."
VR allowed precise control, eliminating sensory confounds like sounds or smells. "In a real world, animals might detect the door through touch or scent, bypassing time judgment," Dombeck adds. "VR removes those variables."
Beyond behavior, the team used two-photon microscopy for high-resolution brain imaging. As mice approached the invisible door, spatial neurons fired; upon stopping, they quieted, and 'time cells' activated—a surprising discovery.
These time cells fired only during pauses, encoding the duration of stillness. "They track precisely how long the animal has been waiting," Dombeck says.
