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What happens in your brain while watching a movie
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What happens in your brain while watching a movie

By scanning people’s brains while they watched movie clips, scientists created the most detailed functional brain map to date. The fMRI analysis, published Nov. 6 in the journal Cell Press Neuronshows how different brain networks light up when participants watched short clips from a range of independent and Hollywood films, including Start, The social networkand Alone at home. The team identified different brain networks involved in processing scenes with people, inanimate objects, actions and dialogue. They also revealed how different executive networks are prioritized during easy versus hard scenes to watch.

“Our work is the first attempt to get a look at different areas and networks of the brain under naturalistic conditions,” says first author and neuroscientist Reza Rajimehr of the 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 functional brain 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 the fMRI scan could provide insight into how the brain’s functional networks respond to complex audio and visual stimuli.

“With resting-state fMRI, there’s no stimulus—people are just thinking internally, so you don’t know what activated these networks,” says Rajimehr. “But with our movie stimulus, we can go back and figure out how different brain networks respond to different aspects of the movie.”

To map the brain during movie viewing, the researchers used an fMRI dataset previously collected from the Human Connectome Project, consisting of whole-brain scans from 176 young adults, which were obtained while the participants watched short clips of 60 minutes from a series of independent programs. and Hollywood movies.

The researchers averaged the brain activity across all participants and used machine learning techniques to identify brain networks, particularly in the cerebral cortex. They then examined how the activity within these different networks related to the content of the movie scene by scene — which included people, animals, objects, music, speech and narration.

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 people and inanimate objects, speech and social interactions.

They also showed an inverse relationship between “executive control areas” – brain regions that allow people to plan, solve problems and prioritize information – and brain regions with more specific functions. When the film’s content was difficult to follow or ambiguous, there was increased activity in brain regions with executive control, but during easier-to-understand scenes, brain regions with specific functions, such as language processing, predominated.

“Executive control areas are typically active in difficult tasks when the cognitive load is high,” says Rajimehr. “It appears that when movie scenes are fairly easy to understand, for example, if there is a clear conversation, the language areas are active, but in situations where there is a complex scene involving context, semantics and ambiguity in scene meaning, it is greater cognitive effort is required, and so the brain switches to using the general domains of executive control.”

Because the analyzes in this paper were based on average brain activity, the researchers say 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 individual subject maps, which would allow us to relate each subject’s individualized map to that subject’s behavioral profile,” says Rajimehr. “We are now studying more deeply how the specific content in each film frame drives these networks – for example, the semantic and social context or the relationship between people and the background scene.”