Depends on whether you're watching Disney or Tarantino
Cell Press
"Our work is the first attempt to get a layout of different areas and networks of the brain during naturalistic conditions," says first author and neuroscientist Reza Rajimehr of Massachusetts Institute of Technology (MIT).
Different areas of the brain are highly interconnected, and
these connections form functional networks that relate to how we perceive
stimuli and behave. Most studies of brain functional networks have been based
on fMRI scans of people at rest, but many parts of the brain or cortex are not
fully active in the absence of external stimulation.
In this study, the researchers wanted to investigate whether
screening movies during fMRI scanning could provide insight into how the
brain's functional networks respond to complex audio and visual stimuli.
"With resting-state fMRI, there is no stimulus --
people are just thinking internally, so you don't know what has activated these
networks," says Rajimehr. "But with our movie stimulus, we can go
back and figure out how different brain networks are responding to different
aspects of the movie."
To map the brain during movie watching, the researchers
leveraged a previously collected fMRI dataset from the Human Connectome
Project, consisting of whole brain scans from 176 young adults that were
obtained while the participants watched 60 minutes' worth of short clips from a
range of independent and Hollywood films.
The researchers averaged the brain activity across all
participants and used machine learning techniques to identify brain networks,
specifically within the cerebral cortex. Then, they examined how activity
within these different networks related to the movie's scene-by-scene content
-- which included people, animals, objects, music, speech, and narrative.
Their analysis revealed 24 different brain networks that
were associated with specific aspects of sensory or cognitive processing, for
example recognizing human faces or bodies, movement, places and landmarks,
interactions between humans and inanimate objects, speech, and social
interactions.
They also showed an inverse relationship between
"executive control domains" -- brain regions that enable people to
plan, solve problems, and prioritize information -- and brain regions with more
specific functions. When the movie's content was difficult to follow or
ambiguous, there was heightened activity in executive control brain regions,
but during more easily comprehendible scenes, brain regions with specific
functions, like language processing, predominated.
"Executive control domains are usually active in
difficult tasks when the cognitive load is high," says Rajimehr. "It
looks like when the movie scenes are quite easily comprehendible, for example
if there's a clear conversation going on, the language areas are active, but in
situations where there is a complex scene involving context, semantics, and
ambiguity in the meaning of the scene, more cognitive effort is required, and
so the brain switches over to using general executive control domains."
Since the analyses in this paper were based on average brain
activities, the researchers say that future research could investigate how
brain network function differs between individuals, between individuals of
different ages, or between individuals with developmental or psychiatric
disorders.
"In future studies, we can look at the maps of
individual subjects, which would allow us to relate the individualized map of
each subject to the behavioral profile of that subject," says Rajimehr.
"Now, we're studying in more depth how specific content in each movie
frame drives these networks -- for example, the semantic and social context, or
the relationship between people and the background scene."
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