Time can be a confusing concept. As much as we all would like to at certain moments, one can’t just reach out and touch time. It’s all around us and dictates quite literally everything in our lives, but in many ways, it’s as mysterious as Bigfoot or Area 51. Focus on the passing of time and 10 minutes can feel like an eternity, but look back on the past year and it feels like it flew by in an instant. It seems time is malleable and subjective yet coldly objective and unwavering all at once.
Some argue that time is nothing more than a side effect of our own consciousness, but all those aches, pains, and eventual gray hairs beg to differ. Time is most certainly real, as the setting sun and rising tide attest on a daily basis.
While it’s been agreed upon for some time that the human body keeps track of passing hours and days via its circadian clock (feeling tired in the evening, waking up in the morning), how exactly our minds measure the passing of seconds has remained up for debate.
Fast forward to today and a new study from the University of California, Los Angeles concludes that the human brain measures passing seconds primarily by counting patterns of cellular activity. The research team used an analogy of falling dominoes to illustrate their findings. Each neuron in a sequence activates the next, and our brains keep track of seconds by noting which neuron is active at a given moment.
So, to wrap up the domino example; if it takes a line of dominos 30 seconds to fall in sequence, the mind knows that 15 seconds have passed by the time that middle domino (neuron) has fallen (activated).
Each passing second isn’t something we all focus on all that often, but the ability to measure and anticipate individual clusters of seconds is a vital perception. You use this ability anytime you operate a car or motorcycle and anticipate breaking at an upcoming red light. Similarly, imagine seeing your supervisor approaching your desk out of the corner of your eye. In that scenario, you would probably have a decent idea of how many seconds you have to spare before he or she arrives for a chat.
In short, take away the human mind’s ability to measure seconds, and suddenly everyday life becomes a whole lot more difficult.
How did the team at UCLA come to these conclusions? A group of lab mice was conditioned to react to two very distinct smells. The first smell always preceded a sweet treat after three seconds had passed. The second smell predicted a sweet liquid after six seconds had passed.
After the mice had experienced the smells and rewards a few times, the rodents started licking their feeding tube earlier after smelling the first scent. This behavior confirmed that the mice had picked up on the smell/food pattern, and had started to anticipate and predict passing seconds.
While all of this was happening, each rodent’s brain was also recorded in order to investigate the neural machinations behind this observed behavior.
First off, researchers noted that two distinct brain regions appeared to be keeping track of time – the premotor cortex and the striatum. Neural activity patterns within the striatum followed the aforementioned sequential (domino) pattern more closely than the premotor cortex.
That being said, the study’s authors conclude that neural sequencing appears to be the mind’s main avenue of measuring and representing the passing of individual seconds and moments.
The full study can be found here, published in Neuron.