Nav: Home

The spotlight of attention is more like a strobe

August 22, 2018

You don't focus as well as you think you do.

That's the fundamental finding of a team of researchers from Princeton University and the University of California-Berkeley who studied monkeys and humans and discovered that attention pulses in and out four times per second.

"Our subjective experience of the visual world is an illusion," said Sabine Kastner, a professor of psychology and the Princeton Neuroscience Institute (PNI). "Perception is discontinuous, going rhythmically through short time windows when we can perceive more or less."

The researchers use different metaphors to describe this throb of attention, including a spotlight that waxes and wanes in its intensity. Four times per second -- once every 250 milliseconds -- the spotlight dims and the house lights come up. Instead of focusing on the action "onstage," your brain takes in everything else around you, say the scientists.

Their work appears as a set of back-to-back papers in in the Aug. 22 issue of Neuron; one paper focuses on human research subjects, the other on macaque monkeys.

"The question is: How can something that varies in time support our seemingly continuous perception of the world?" said Berkeley's Randolph Helfrich, first author on the human-focused paper. "There are only two options: Is the data wrong, or is our understanding of our perception biased? Our research shows that it's the latter. Our brains fuse our perceptions into a coherent movie -- we don't experience the gaps."

Perception doesn't flicker on and off, the researchers emphasized, but four times per second it cycles between periods of maximum focus and periods of a broader situational awareness.

"Every 250 milliseconds, you have an opportunity to switch attention," said Ian Fiebelkorn, an associate research scholar in PNI and the first author on the macaque-focused paper. You won't necessarily shift your focus to a new subject, he said, but your brain has a chance to re-examine your priorities and decide if it wants to.

Brain rhythms have been known for almost a century, since electroencephalograms -- better known as EEGs -- were invented in 1924. "But we didn't really understand what these rhythms are for," said Kastner, who was the senior author on both papers. "We can now link brain rhythms for the first time to our behavior, on a moment-to-moment basis. ... This is a very surprising finding, more since these rhythmic processes are evolutionarily old -- we find them in non-human primates as well as in our own species."

This pulsing attention must present an evolutionary advantage, the researchers suggest, perhaps because focusing too intently on one subject could allow a threat to catch us by surprise.

"Attention is fluid, and you want it to be fluid," said Fiebelkorn. "You don't want to be over-locked on anything. It seems like it's an evolutionary advantage to have these windows of opportunity where you're checking in with your environment."

"It's an elegant way to allocate brain resources -- to sample the environment and not have any lapses," said Robert Knight, a professor of psychology and neuroscience at Berkeley and a co-author on the human-focused paper.

Kastner's lab focuses on macaque research, so she reached out to Knight's lab, which does similar studies on humans. The resulting papers are unprecedented, Knight said.

"This is cross-species validation of a fundamental aspect of human behavior," he said. "I have not seen any back-to-back human and monkey papers appear anywhere ... and these are in the same issue of Neuron, a preeminent journal."

Fiebelkorn agreed: "We have an assumption that what we find in the monkey will hold up in humans, but it's rarely checked as carefully as it is here."

"Originally, we wanted to study something very different," said Kastner. "We wanted to ask how we can select objects from our cluttered visual environments. ... We were particularly looking at how the intake of visual information unfolds over time -- something that is rarely done in behavioral studies -- and this revealed the rhythmic structure of perception. It was a complete surprise finding."
-end-
"A dynamic interplay within the frontoparietal network underlies rhythmic spatial attention" by Ian Fiebelkorn, Mark Pinsk and Sabine Kastner (DOI: 10.1016/j.neuron.2018.07.038) and "Neural mechanisms of sustained attention are rhythmic" by Randolph Helfrich, Ian Fiebelkorn, Sara Szczepanski, Jack Lin, Josef Parvizi, Robert Knight and Sabine Kastner (DOI: 10.1016/j.neuron.2018.07.032) were supported by the Alexander von Humboldt Foundation (Feodor Lynen Research Fellowship), an intramural fellowship from the University of Oslo Department of Psychology, the McDonnell Foundation and several grants from the National Institute of Health: R01MH109954, R37NS21135, training fellowship F32EY023465, the National Institute of Mental Health grant R01MH064063, the Silvio O. Conte Center grant 1P50MH109429, and the National Eye Institute grants RO1EY017699 and R21EY023565.

Princeton University

Related Brain Articles:

Study describes changes to structural brain networks after radiotherapy for brain tumors
Researchers compared the thickness of brain cortex in patients with brain tumors before and after radiation therapy was applied and found significant dose-dependent changes in the structural properties of cortical neural networks, at both the local and global level.
Blue Brain team discovers a multi-dimensional universe in brain networks
Using a sophisticated type of mathematics in a way that it has never been used before in neuroscience, a team from the Blue Brain Project has uncovered a universe of multi-dimensional geometrical structures and spaces within the networks of the brain.
New brain mapping tool produces higher resolution data during brain surgery
Researchers have developed a new device to map the brain during surgery and distinguish between healthy and diseased tissues.
Newborn baby brain scans will help scientists track brain development
Scientists have today published ground-breaking scans of newborn babies' brains which researchers from all over the world can download and use to study how the human brain develops.
New test may quickly identify mild traumatic brain injury with underlying brain damage
A new test using peripheral vision reaction time could lead to earlier diagnosis and more effective treatment of mild traumatic brain injury, often referred to as a concussion.
This is your brain on God: Spiritual experiences activate brain reward circuits
Religious and spiritual experiences activate the brain reward circuits in much the same way as love, sex, gambling, drugs and music, report researchers at the University of Utah School of Medicine.
Brain scientists at TU Dresden examine brain networks during short-term task learning
'Practice makes perfect' is a common saying. We all have experienced that the initially effortful implementation of novel tasks is becoming rapidly easier and more fluent after only a few repetitions.
Balancing time & space in the brain: New model holds promise for predicting brain dynamics
A team of scientists has extended the balanced network model to provide deep and testable predictions linking brain circuits to brain activity.
New view of brain development: Striking differences between adult and newborn mouse brain
Spikes in neuronal activity in young mice do not spur corresponding boosts in blood flow -- a discovery that stands in stark contrast to the adult mouse brain.
Map of teenage brain provides evidence of link between antisocial behavior and brain development
The brains of teenagers with serious antisocial behavior problems differ significantly in structure to those of their peers, providing the clearest evidence to date that their behavior stems from changes in brain development in early life, according to new research led by the University of Cambridge and the University of Southampton, in collaboration with the University of Rome Tor Vergata in Italy.

Related Brain Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Jumpstarting Creativity
Our greatest breakthroughs and triumphs have one thing in common: creativity. But how do you ignite it? And how do you rekindle it? This hour, TED speakers explore ideas on jumpstarting creativity. Guests include economist Tim Harford, producer Helen Marriage, artificial intelligence researcher Steve Engels, and behavioral scientist Marily Oppezzo.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".