Neurology

Study identifies a new way by which the human brain marks time

neurosciencestuff:

With a little help from HBO’s “Curb Your Enthusiasm,” University of
California, Irvine neurobiologists have uncovered a key component of how
the human brain marks time.

Using high-powered functional MRI on college students watching the
popular TV show, they were able to capture the processes by which the
brain stores information related to when events happen, or what is known
as temporal memory. The study appears in Nature Neuroscience.

The researchers identified a new network of brain regions involved in these processes, confirming in humans the results of rat studies
reported last summer by Nobel laureate Edvard Moser and colleagues, who
pinpointed the nerve cells in the same areas that give each moment a
distinctive signature. A News & Views article in Nature Neuroscience highlights how these findings fit together.

Michael Yassa, director of UCI’s Center for the Neurobiology of
Learning & Memory and senior author on the study, said the research
may further understanding of dementia, as these temporal memory regions
are the first to experience age-related deficits and also show some of
the first pathological hallmarks of Alzheimer’s disease, most notably
tangles.

“Whether these alterations have consequences for time-related memory
remains to be seen; it’s something that we are currently testing,” he
added.

Real-time brain imaging

In the UCI study, participants sat with their heads inside a
high-resolution fMRI scanner while watching the TV show and then viewing
still frames from the episode, one at a time.

The researchers found that when subjects had more precise answers to
questions about what time certain events occurred, they activated a
brain network involving the lateral entorhinal cortex and the perirhinal
cortex. The team had previously shown
that these regions, which surround the hippocampus, are associated with
memories of objects or items but not their spatial location. Until now,
little had been known about how this network might process and store
information about time.

“The field of neuroscience has focused extensively on understanding
how we encode and store information about space, but time has always
been a mystery,” said Yassa, a professor of neurobiology & behavior.
“This study and the Moser team’s study represent the first
cross-species evidence for a potential role of the lateral entorhinal
cortex in storing and retrieving information about when experiences
happen.”

“Space and time have always been intricately linked, and the common
wisdom in our field was that the mechanisms involved in one probably
supported the other as well,” added Maria Montchal, a graduate student
in Yassa’s lab who led the research. “But our results suggest
otherwise.”

Testing time-related memory

Yassa said it’s worth noting that his group published another report last year in Neuron
showing that the lateral entorhinal cortex is dysfunctional in older
adults with lower-than-average memory performance. That study did not
test memory for time but rather discrimination memory for similar
objects.

Most studies examining time in the laboratory employ static objects
on a computer screen, Yassa said, but they tell very little about how
the brain processes information in the real world. This is why the UCI
study used “Curb Your Enthusiasm,” a situational comedy that mirrors
real life, as it involves people, scenes, dialogue, humor and narrative.

“We chose this show in particular because we thought it contained
events that were relatable, engaging and interesting,” he said. “We also
wanted one without a laugh track. Interestingly, while the show is
hilarious for some of us, it did not seem to instigate a lot of laughter
among the college undergraduates we tested – which was excellent for
us, as we needed to keep their heads inside the scanner.”

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