However, the scientists, from the Champalimaud Centre for the Unknown, in Lisbon, decided to look at a type of dopamine-releasing neurons in a part of the brain called the ‘substantia nigra pars compacta’, because these neurons are linked to the emotions that can change time perceptions.

How mice judge the passing of time

The scientists started by training mice to perform a task that involved estimating whether the duration of the interval between two sounds was shorter or longer than 1.5 seconds. To give their answer, the mice had to place their snout either right if the interval was shorter, or left, if it was longer. If they answered correctly, they received a reward.

Next, the researchers measured the activity of dopamine neurons in the substantia nigra pars compacta during the task, and identified an increase in neural activity during the two sounds, indicating that this area of the brain was involved in estimating how much time elapsed.

However, it wasn’t clear at that point if these neurons actually controlled subjective perceptions of time or just objective estimations. “The neurons seemed to reflect information about the estimation of duration by the animals. But might they actually be controlling their sense of time?” asked lead author Joe Paton.

Lab Mouse
The mice were trained to perform a task that involved estimating time durationPeter Parks/Getty

The scientists performed another experiment, using the technique of optogenetics lights that flicker at a certain frequency – to stimulate or silence neurons. It appeared that manipulating the neurons in the substantia nigra pars compacta in this way changed the mice’s ability to succeed in the task, suggesting changes in their perceptions of time.

“We found that if we stimulated the neurons, the mice tended to underestimate duration, and if we silenced them, they tended to overestimate it”, Paton explains. “This result, together with the naturally occurring signals we observed in the previous experiments, demonstrate that the activity of these neurons was sufficient to alter the way the animals judged the passage of time. This was the major result of our study.”

This study had only been conducted in animals, so it is not clear whether these findings could be applied to humans, although the scientists believe possible that a similar circuit may be at work in our brains. – IBTimes