Why does our internal clock interpret time differently depending on what we do and how we feel? We have all experienced the effect when pleasant moments fly by instantly, and it seems like it takes forever to wait for food to warm up in the microwave. Although everyone knows (if you do not take into account the theory of relativity) that time always flows the same way – at a friendly party, and at a boring office meeting.
How does the brain keep track of time?
Our brains actually contain not one, but two separate systems for measuring time.
The body uses one of the systems to determine our time position during the day. These internal clocks, which cycle things like eating, sleeping, digestion, and even the immune system, are called the circadian rhythm.
And although the circadian system is controlled from the inside by the production of special proteins in a 24-hour cycle, at the same time, it is largely dependent on external factors, for example, the daily change in illumination. That is why staring at a smartphone screen before bed makes it difficult to fall asleep – bright light makes the brain mistakenly believe that it is morning and it is time to wake up. The same mechanisms tell nocturnal animals when to go hunting and sunflowers where to turn during the day.
In addition to this internal clock that synchronizes multiple bodily functions, our brains are also able to track time in a given situation, allowing us to determine how much time has passed from the start and create a mental estimate of the length of time. For example, these clocks allow us to perform actions for an adequate amount of time, assess whether the time during which we are waiting for an event is acceptable, and they are also responsible for the ability to determine how quickly to respond to an event, for example, to catch ball.
This clock determines time differently from the circadian system. Neuroscientist Professor Dean Buonomano believes that when the brain processes sensory information, “it triggers a cascade of reactions between brain cells. Each reaction leaves a trail that allows the network of brain cells to encode time. ”
Our brain’s clock, designed to track and evaluate the passage of time, is a complex system that not only measures the current time, but also constantly records the amount of time that has passed.
Why does it sometimes seem that time flies and sometimes stands still?
A publication recently published in the Journal of Neuroscience may shed light on why time sometimes seems to move faster, and sometimes it drags on and on and on …
The study found that neurons in an area of the brain called the supramarginal gyrus (SMG) periodically fire in response to external stimulation. When we are constantly exposed to these neurons firing over a long period of time, the supra-marginal gyrus experiences fatigue and the neuron signals begin to slow down slightly. As the rest of our brain systems continue to operate at their normal speed, the relative displacement between the time measurement system and the rest of the systems makes us feel like time moves slowly.
How do researchers study our perception of time?
The authors of the work, Japanese neurophysiologists Hayashi and Ivri, studied the brain activity of healthy people using functional MRI. Participants were given tasks to compare time intervals while taking measurements of brain function.
To begin with, participants were shown a visual stimulus (gray circle) for a fixed interval 30 times in a row. Then they showed a test signal and asked how long the test demonstration lasted.
It was found that when the initial signal was short, the participants tended to overestimate the length of the test image, and vice versa, with a long initial signal, they perceived the test image as shorter.
When examining the brain activity of the subjects, the researchers found a marked correlation between how accurately the subject was timing and the activity of the SMG region; as the activity in this zone increased, the timing became less accurate.
How do these discoveries affect our understanding of time perception?
In the past, the dominant idea was that an area of the brain called the striatum, or striatum, was responsible for virtually all bodily functions related to the perception of time. This new study, combined with others, demonstrates the importance of the hippocampus in identifying and remembering periods of time, and suggests that we may be using more parts of the brain to track time than is commonly believed.