You know the saying: Time flies when you’re having fun.
A recent discovery by researchers from the University of California, Los Angeles (UCLA), suggests a hit of the brain’s “feel-good” chemical, dopamine, may have a rather surprising effect on our perception of past experiences, drawing out novel moments in our memories.
In this new research, scans revealed that a dopamine-producing region of the midbrain, known as the ventral tegmental area (VTA), becomes active when we’re alerted to the start of a new sequence of events. What’s more, the harder this small patch of neurons works, the more time appears to pass between events separated into different sequences. It’s as if a burst of dopamine stretches out the moments, dividing a continuous experience into clear chapters for easier reflection.
“We found that activation of the dopamine system at the beginning of a new event is likely one of the ways that our brain segments experiences into memorable episodes,” says Erin Morrow, a doctoral student at UCLA and lead author on the study.
Commonly associated with reward, dopamine plays vital roles in executive function, behavioral reinforcement, and control of movement.
It may also be critical for our memory. Cells in the VTA respond to novel experiences, signaling unpredictable moments worthy of our attention. According to the dopamine clock hypothesis, the neurotransmitter is intimately connected to our brain’s timing system. Turn on the dopamine tap, and we’ll overestimate just how many seconds have ticked by.
Whether that time dilation cements itself into our long-term memory is a question Morrow and her team set out to answer using an fMRI scanner, an eye tracker, and a simple memory test.
A group of 32 volunteers was asked to pay close attention to a series of images representing ordinary objects and determine which were larger than a shoebox. Each picture was preceded by a brief tone projected into the volunteer’s left or right ear. After eight images, the researchers changed the tone’s pitch, the ear in which it was projected, and the hand participants were required to use to communicate their estimates of object sizes, definitively breaking the sequence into four distinct sections.
Scans showed the volunteers’ VTAs light up with each change, suggesting dopamine had triggered a response. An increase in blinking further demonstrated that dopamine was probably at work.
Following each sequence, volunteers were asked about the order and timing of specific pairs of objects. Despite the fact time between each of the paired images remained constant, volunteers reported pictures separated into different sections were further apart in time.
Taken together, the experiment suggests our reconstruction of past events is malleable, and often inaccurate, depending largely on dopamine’s ability to fragment life’s experiences into chapters.
“We think the time dilation effect we found is useful, even though it’s not accurate, because it may help push those experiences farther apart in memory,” says Morrow.
It’s hard to say whether the results accurately represent fluctuating dopamine levels under real-world conditions. Future experiments are needed to confirm the neurotransmitter’s role in turning surprising events into teaching moments.
Based on these findings, however, we may have dopamine to thank for compressing life’s more boring episodes, filling our memories instead with long moments of joy, surprise, and excitement.
The study was published in the journal Nature Communications.
Source: University of California, Los Angeles
Fact-checked by Bronwyn Thompson
