The passage of time is an objective measure. A minute is 60 seconds, and an hour is 60 minutes and so on. However, the brain processes time in the realm of memories and experiences, so it's not always as clear-cut as minutes and seconds.
A recent study by researchers at the Kavli Institute for Systems Neuroscience in Norway shows that there is a specific network of cells in the brain that expresses our sense of time and folds it into memories and experiences, so it's a complete concept
Edvard Moser, a Nobel laureate and director of the Kavli Institute, which is based at the Norwegian University of Science and Technology (NTNU) explained, "This network provides timestamps for events and keeps track of the order of events within an experience. This area of the brain where time is experienced is located right next to the region that codes for space."
Clocks were created to define time. Appointments, work schedules, and events all depend on knowing when to begin and when to end. Standardization of these matters is essential for society to function. That isn't how the brain works, however. Time, in the mind, is intricately woven into our memories and our experiences. It's entirely different than minutes and seconds.
The concept of a "neural clock" is similar to the circadian rhythm of day and night; only it's internal and somewhat subjective. In the brain, cells in the hippocampus act as a timescale that allows us to remember experiences that last ten seconds, ten minutes or ten hours, but these memories are not defined by their duration. It's this part of the brain that helps us adapt to the external concept of time. Previous research by May-Britt Moser and Professor Moser along with Dr. John O'Keefe on the brain's positioning system resulted in the team sharing the 2014 Nobel Prize for Physiology or Medicine. In that work, the mechanism of how the brain perceives space, that is, where we live and where we go was discovered, but the perception of time has been a bit more challenging to nail down.
The work that the team NTNU's Kavli Institute recently published suggests that in the brain, time is organized by experiences and memories that are in order, but according to subjective criteria, not merely minutes and seconds. Albert Tsao who was an author on the work on time, and who was a Ph.D. candidate during the Nobel research, wrote, "Our study reveals how the brain makes sense of time as an event is experienced. The network does not explicitly encode time. What we measure is rather a subjective time derived from the ongoing flow of experience." Mostly, in the brain, the clock is subjective and based on experiences and events, not mathematical units.
Tsao concentrated on the lateral entorhinal cortex (LEC). This area of the brain is right next to the medial entorhinal cortex (MEC) which is where Prof. Moser had found the cell signaling network that processed space. Unlike the cells for space, the LEC was a moving target. Signals changed all the time, and no real pattern could be found that showed how the brain was keeping time. Once the team realized that the signals changed over time, the pieces of the puzzle came together. The brain organized time as events and memories, not merely locations and data points. Moser explained, "Time is a non-equilibrial process. It is always unique and changing. If the network was indeed coding for time, the signal would have to change with time in order to record experiences as unique memories."
Tsao and Moser, along with colleagues at the Kavli Institute believe this is the "neural clock" that the brain uses to keep track of time. Further experiments with lab rats recorded cell signaling in the brains of rats as they wandered around a new environment in timed trials. These signals were how the rats were marking time, in small bits of episodic memory. Moser explained that the study shows that how we perceive time can be changed by switching up the activities you engage in and the content of your experiences. It might seem all timey-wimey and wibbly-wobbly, but the brain has a way of organizing our perception of time. Check out the video to learn more about this new research.
Sources: Nature, Norwegian University of Science and Technology