Researchers from the University of Nevada, Las Vegas (UNLV) have discovered interesting facts about how our brain perceives the flow of time.

People often think that our brains are synchronized with artificial clocks on electronic devices, counting time in very precise, minute intervals. However, a study published this month in the journal Current Biology shows that our brains do not function that way.

By analyzing changes in brain activity, the research team found that we base our perception of time on the number of experiences we have, rather than on some kind of internal clock. Furthermore, increasing the speed or intensity of activities affects the way the brain perceives time.

Perception of Time Through Experiences
James Hyman, an associate professor of psychology at UNLV and the lead author of the study, explains: "We gauge time through the activities we perform and the events we experience. When we are calm and nothing is happening, time seems slow. Conversely, when we experience many events, each of them propels our brain forward. If the brain measures time through experiences, more activities mean faster passage of time."

Methodology and Results
The study examined activity in the anterior cingulate cortex (ACC), a part of the brain important for tracking activities and experiences. Researchers observed rodents that had to respond to stimuli 200 times.

It is already known that brain patterns are similar, but not identical, each time we perform repetitive actions. The aim of the study was to determine whether differences in brain patterns could be detected during the first and two-hundredth actions, and whether the time required to complete a series of actions affected brain activity.

By comparing changes in patterns during the task, researchers noticed that brain patterns change from the beginning to the middle and end of the task. Regardless of the speed at which the animals moved, the patterns followed the same path. The patterns were consistent when researchers applied a machine learning-based mathematical model to predict the course of brain activity, further confirming that experiences, not time, are responsible for changes in neuron activity.

Hyman illustrated the key findings with a story about two factory workers tasked with making 100 pieces during a shift. One worker completed the task in 30 minutes, and the other in 90 minutes.

"The length of time required to complete the task did not affect brain patterns. The brain does not function as a clock, but as a counter," explains Hyman. "Our brains record a sense of time. For workers making pieces, the difference between making the 85th and 60th piece is clear, but not necessarily between the 85th and 88th piece."

How Does the Brain Count?
Researchers found that, as the brain progresses through a task involving a series of actions, different small groups of neurons begin to cooperate, transferring the task to different groups of neurons every few repetitions, similar to how runners pass a baton.

"Cells cooperate and over time randomly align to perform the task: one cell takes on a few tasks, then another takes on a few tasks," says Hyman. "Cells track actions and thus parts of activity and time during the task."

The study shows that our perception of time applies to activities that are not physical. "We use this part of the brain to track conversations during dinner," says Hyman. "Think about the flow of conversation and you can recall things that happened earlier and later during dinner. However, distinguishing individual sentences in memory is impossible. But you know that at the beginning you talked about one topic, during dessert another, and at the end a third."

Observing rodents working quickly, scientists also concluded that maintaining a good pace helps the perception of time: "The more we work, the faster time passes. They say time flies when we have fun. Instead, maybe we should say 'time flies when we work a lot.'"

Important Conclusions
Although there is already a wealth of information about brain processes on very short time scales of less than a second, Hyman says the UNLV study is revolutionary in studying brain patterns and the perception of time over several minutes to hours – "which is how we live most of our lives: hour by hour."

"This is among the first studies to examine behavioral time scales in this part of the brain called the ACC, which is important for our behavior and emotions," says Hyman.

The ACC is involved in most psychiatric and neurodegenerative disorders, and is important for mood disorders, PTSD, addictions, and anxiety. The function of the ACC is also crucial for various dementias, including Alzheimer's disease, which is characterized by disruptions in the perception of time. The ACC has long been associated with helping people sequence events or tasks such as following recipes, and the research team speculates that their findings on time perception may fall into this context.

Although the findings are revolutionary, more research is needed. Nevertheless, Hyman says preliminary findings offer potentially useful insights into time perception and its possible connection to memory processes in everyday life. For example, researchers speculate that it could help navigate through school tasks or even relationship breaks.

"If we want to remember something, maybe we should slow down by studying in short periods and take time before engaging in the next activity. Give yourself calm times to rest," says Hyman. "On the other hand, if we want to get over something quickly, immediately engage in some activity."

Hyman also emphasizes the strong connection between the ACC, emotions, and cognition. Thinking of the brain as a physical entity that we can manage might help us control our subjective experiences.

"When things go faster, we tend to think it’s more fun – or sometimes overwhelming. But we don’t need to consider it solely as a psychological experience, like fun or overwhelming; instead, if we see it as a physical process, it can be useful," he says. "If it’s overwhelming, slow down or, if you’re bored, add activities. People already do this, but it’s empowering to know that it’s a way to work on our own mental health because our brains already work this way."

Source: University of Nevada