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. Erin Morrow, a doctoral student at UCLA and lead author on the study, says the findings suggest that dopamine activation at the start of a new event is likely one of the ways the brain segments experiences into memorable episodes.
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. After every eight images, the researchers changed several cues simultaneously — the tone's pitch, which ear it played into, and the hand used to respond — 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. Morrow notes that while the time dilation effect is not accurate, it may be useful — helping push distinct experiences further apart in memory, making them easier to distinguish and recall.
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.