By Alex Russell, College of Letters and Science
How we focus our attention before we even see an object matters. For example, when we look for something moving in the sky, our expectation would be very different if the object is a bird flying past or a baseball coming straight at us.
But it's unclear whether our brain's attention focuses first on a broad characteristic of the anticipated object, such as movement, or a specific feature — such as the direction of movement up or down.
Researchers from the Center for Mind and Brain at the University of California, Davis, addressed this by analyzing electrical brain activity with machine-learning methods while human volunteers prepared to see colored dots moving on a screen. The study found that the brain's attention focus starts with a broad category, then narrows down to the specific feature of interest. The study was published Aug. 19 in The Journal of Neuroscience .
"Our study tells us that our brains first prepare to focus attention by activating neurons representing the broad category of the anticipated object and then quickly sharpens that focus," said George R. Mangun , a Distinguished Professor of psychology and neurology and co-director of the UC Davis Center for Mind and Brain. "This means that the brain's attention mechanisms are organized in a hierarchy such that it prepares for perceiving a stimulus by narrowing the focus of our attention over time."
Clocking brain activity
Researchers combined electroencephalogram, or EEG, data with eye tracking and machine learning to study "anticipatory attention," which is attention that enables a person to prepare to perceive upcoming sensory events. The EEG data reflects the brain's electrical activity down to the millisecond using electrodes worn on the scalp.
The study took place in 2024 using 25 participants between 19 and 39 years of age.
The research team measured how long it took the brain to get ready to pay attention to colored dots moving on the screen. The goal was to learn whether the brain's attention first prepared for a broad feature category of an object of interest, such as color or movement, before attention could be narrowed to a specific feature, such as a specific color or direction of movement.
The timer began with a blank screen when researchers cued participants to look for only a blue or green dot, or for a dot moving up or down. The timer stopped when the dots appeared.
"When attention is directed to the color of the moving dots, it suppresses attention to the direction of motion, and vice versa," said Sreenivasan Meyyappan , an assistant project scientist at the Center for Mind and Brain and the study's lead author. "This broad focus of attention is then narrowed further to suppress the irrelevant colors as well, supporting processing of the specific color or motion of interest."
The machine-learning software separated brain activity for each of the general and specific features. It revealed a difference measured in milliseconds. A millisecond is a thousandth of a second.
Anticipatory attention to the dot's general category — color or direction of movement— took 240 milliseconds on average to establish in the brain. Attention to the dot's specific feature — blue or green, or up and down — took longer, with an average time of 400 milliseconds.
"The control systems involved in attention are broadly tuning the brain first, and then narrowing it down," said Mangun. "It's like a pilot flying a plane toward Europe and then toward the end zooming in on Rotterdam and not Berlin."
Building a more complete picture of how the brain works can provide important insights related to brain health, said Mangun. For example, future research might find that people with disordered attention, such as those with attention-deficit hyperactivity disorder or autism, experience delays in narrowing the focus of attention.
"Understanding more about how the brain focuses its attention would tell us what parts of the system are not operating properly and might lead to different perceptual or behavioral symptoms down the line, and therefore different treatment approaches" said Mangun.
Mingzhou Ding , Distinguished Professor and J. Crayton Pruitt Family Professor of biomedical engineering at the University of Florida, is an additional co-author on this study.
The research was supported by National Institutes of Health and the National Science Foundation.
