New Study Reveals How Visual Clutter Alters Brain's Processing of Visual Information
In a new study published in the journal Neuron, Yale researchers have discovered that visual clutter influences how visual information flows through the brain and that the clutter’s exact location in our visual field also affects this processing. These insights shed new light on the neural basis of perception and deepen our understanding of how the visual cortex works.
“Previous research indicated that visual clutter impacts how we perceive the target in our focus, with differences depending on where that clutter is in relation to our current focus,” Anirvan Nandy, PhD, assistant professor of neuroscience at Yale School of Medicine and co-senior author of the study, said in a YaleNews article. He illustrates this with the difficulty of reading out of the corner of one’s eye: if someone tries to read the word “cat” peripherally, the final letter ‘t’ will interfere more with identifying the central letter ‘a’ than the initial letter ‘c’—even though they’re equally spaced. This well-known phenomenon, called “visual crowding,” is the reason people struggle to distinguish objects or letters when they are near clutter in peripheral vision.
In this study, the research team set out to explore what happens in the brain when clutter is present in a visual scene. Using macaque monkeys, whose visual processing closely mirrors that of humans, they conducted an experiment where the monkeys fixated on the center of a screen displaying visual stimuli in both central and peripheral areas. Researchers then recorded activity in the primary visual cortex, the part of the brain that first processes visual information.
The study found that while the specific location of clutter didn’t alter the sequential flow of information between neurons in the visual cortex, it did affect the efficiency of this flow. Dr. Monika Jadi, co-senior author and assistant professor of psychiatry at Yale, compared this to a phone tree: “It’s like passing a message along a series of calls. The clutter’s location might not change the sequence of calls, but it can impact how clearly each person receives the message.”
The team also discovered a previously unknown property of the visual cortex, which could bridge gaps between different fields of visual research. It has long been established that information travels from one area of the visual cortex to the next in a hierarchical order, helping to build a complete visual representation. However, this study found that smaller, specialized subunits within each cortical area perform their own unique computations. Not all information processed within these subunits is passed along, which helps to explain differences in how visual information is integrated at different stages of visual processing.
The researchers now aim to study how clutter might affect information flow between different brain regions and how attention could impact this flow. “For instance, when driving, you might be looking at the car in front of you, but you’re also paying attention to the car in the next lane,” said Dr. Nandy. “The visual focus is on the car ahead, but attention can help us gather critical information from peripheral areas we aren’t directly looking at.”
The next phase of the research will address questions about how the brain uses attention to filter and enhance visual information in crowded scenes, allowing us to perceive beyond our point of focus.
The research was funded by the National Eye Institute and involved contributions from Xize Xu, a post-doctoral fellow, and Mitchell Morton, a former post-doctoral associate at Yale School of Medicine.