Researchers from the Massachusetts Institute of Technology (MIT) have created the most detailed functional map of the brain's cerebral cortex to date, as reported in the journal Neuron. The neuroscientists scanned the brains of 176 young adults while they watched movie clips for 60 minutes, using data from the Human Connectome Project. This innovative study aimed to investigate how brain networks respond to complex auditory and visual stimuli by screening movies during functional Magnetic Resonance Imaging (fMRI) scanning.
The research team, led by Robert Desimone, director of MIT's McGovern Institute for Brain Research, and including John Duncan, utilized a new approach that reveals a more comprehensive picture of brain function during natural tasks. "There's an emerging approach in neuroscience to look at brain networks under more naturalistic conditions. This is a new approach that reveals something different from conventional approaches in neuroimaging," Desimone said.
Using a machine-learning algorithm to analyze the activity patterns of each brain region, the researchers identified 24 brain networks associated with specific aspects of sensory or cognitive processing. These networks included those involved in "executive control" that were most active during transitions between different clips. Many of these networks have been seen before, but this technique offers a more precise definition of where the networks are located. "Different regions are competing with each other for processing specific features, so when you map each function in isolation, you may get a slightly larger network because it is not getting constrained by other processes," explained Reza Rajimehr, the first author of the paper and a neuroscientist at MIT. "But here, because all the areas are considered together, we are able to define more precise boundaries between different networks."
The fMRI analysis showed how different brain networks light up when participants viewed short clips from a range of independent and Hollywood films, including "Inception," "The Social Network," and "Home Alone." The researchers calculated the average brain activity of all participants and used machine learning techniques to identify functional networks related to how we perceive stimuli and behave. Some of the identified networks were located in sensory areas such as the visual and auditory cortices, consistent with their specific sensory functions.
Within the social processing network, regions specific to processing social information about faces and bodies were identified, along with networks associated with recognizing human faces, movement, places, and social interactions. The research team found that different brain networks were involved in processing scenes with people, inanimate objects, actions, and dialogues, revealing that the brain employs specific networks for these elements.
The study also revealed how different executive networks are prioritized during easy versus hard-to-follow scenes, suggesting that the brain adapts its activity according to the difficulty of the scenes. In scenes that are easy to understand, specialized regions, such as language processing areas, predominate, particularly during clear dialogues. "It seems that when the movie scenes are quite easy to understand, for example if there is a clear conversation, the language areas are active," said Rajimehr. "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."
When the movie's content was difficult to follow or ambiguous, there was heightened activity in executive control brain regions, indicating a reliance on these areas under cognitive strain. The researchers observed that these control networks appear to have a "push-pull" relationship with networks that process specific features such as faces or actions. "Executive control domains are often active in difficult tasks when the cognitive load is high," Rajimehr explained, indicating that in complex scenes, the brain prioritizes these areas to the detriment of specific processing zones.
The researchers hope that their new map will serve as a starting point for further study of what each of these networks is doing in the brain. "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," Rajimehr said.
Since the analyses in this paper were based on average brain activities, the researchers suggest 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," Rajimehr stated.
"This kind of experiment is really about generating hypotheses for how the cerebral cortex is functionally organized," Desimone said. "Networks that emerge during movie watching now need to be followed up with more specific experiments to test the hypotheses. It's giving us a new view into the operation of the entire cortex during a more naturalistic task than just sitting at rest."
The research was funded by the McGovern Institute, the Cognitive Science and Technology Council of Iran, the MRC Cognition and Brain Sciences Unit at the University of Cambridge, and a Cambridge Trust scholarship.
Sources: Mirage News, Milenio, Infobae, Science Daily
This article was written in collaboration with generative AI company Alchemiq