Dopamine may stretch time perception and shape lasting memories
· News-MedicalEver heard of getting a "dopamine hit" from something you enjoy? These exciting moments also appear to influence memory, although perhaps not in the way you'd expect.
New research by UCLA psychologists suggests your brain may use dopamine to distort and expand time between distinct events, separating the flow of experience into pieces that can be flexibly reconstructed in the future.
"Dopamine is often talked about in the media as a chemical that makes things feel rewarding. People say we get a burst of dopamine when we eat food that we like, or when we scroll on social media, for example," said first author and UCLA doctoral student Erin Morrow. "But the dopamine system in our brain also responds strongly to novelty and change. 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.
How do we form durable memories from the steady flow of life's experiences?
When we summon a memory, we may recall events as having unfolded very quickly or having dragged on at unbearable slowness. But that's not actually how time elapsed in the moment. It's somewhat of a puzzle, then, how our brain adds or subtracts time from the original flow of our experiences. This question is important because how our brain constructs new memories is related to how we experience and represent time.
UCLA psychology professor David Clewett studies how the brain marks event boundaries, which are transitions between different noteworthy contexts, to segment experience into a more organized format that can be retrieved later as memory.
"Time is often treated as a physical dimension," said Clewett. "But in psychology, time isn't fixed. It's something the brain constructs and is shaped by experience. As my colleague, professor Dean Buonomano puts it, our sense of time is evolution's way of allowing us to understand change. Our findings suggest that this process also shapes memory. I think of it as inserting small wedges into an otherwise continuous stream, helping neighboring events stand apart."
"The purpose of memory is not always to reconstruct the past completely accurately," said Morrow. "It helps us remember past experiences in the most useful way possible so that we can change our future behavior."
The dopamine system is engaged when new events happen
Researchers asked 32 volunteers to look at pictures of neutral objects while inside an MRI scanner. In between each object, tones were played in either the right or left ear. The same tone was repeated in the same ear across eight consecutive items to create a sense of a coherent event. The tone then switched to the other ear and changed pitch to create an "event boundary," a meaningful change that signaled the current event had ended and the next had begun.
Participants were then presented with pairs of images from the earlier sequence and asked how far apart in time they appeared. However, the "secret" was that the images were all actually the same distance apart in time. Strikingly, participants remembered items that spanned tone switches as occurring farther apart. This finding suggested that the tone switch - and the VTA response accompanying it - had helped separate the objects into different memories. If people blinked more often across this window, they also remembered the items as occurring further apart.
Morrow said that the literature on the relationship between blinking and dopamine is mixed. She pointed out that many studies focus on blinking at rest or in people living with disorders related to atypical dopamine levels. In contrast, the current study took the novel approach of looking at dopamine and blinking while people without diagnosed psychiatric disorders were actively perceiving events.
How does change mark time in human memory?
This study represents an important step toward understanding how dopamine shapes memory. However, there are a few important limitations. These brain scans can't directly measure dopamine release, nor whether it causes time dilation directly. More research is needed to see whether these laboratory-based effects also apply to more complex, real-world experiences.
"Perhaps most importantly, our findings suggest that we don't simply move through time," says Clewett. "It is something we help create. By embracing change and variety, we expand our memories and, in that sense, expand our lives."
The research was funded by the National Institutes of Health.
Source:
University of California - Los Angeles
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