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Which side is which?: How the brain perceives borders

Salk scientists have discovered that neurons deep in the brain’s cortex are the first to compute which side of a visual border is an object and which side is background
November 30, 2021
Optical illusion showing a vase or two faces

In the classic Rubin’s vase optical illusion, neurons in the brain must decide whether the border between black and white belongs to the white area or to the black area, which determines whether you perceive the scene as either a black vase on a white background, or white faces on a black background. Credit: Talking faces by solsken CC BY-NC-SA 2.0

In the classic “Rubin’s vase” optical illusion, you can see either an elaborate, curvy vase or two faces, noses nearly touching. At any given moment, which scene you perceive depends on whether your brain is viewing the central vase shape to be the foreground or background of the picture.

Now, Professor John Reynolds and Senior Postdoctoral Fellow Tom Franken have made headway into understanding how the brain decides which side of a visual border is a foreground object and which is background. The research, published on November 30, 2021 in the journal eLife, sheds light on how areas of the brain communicate to interpret sensory information and build a picture of the world around us.

“The way that the brain organizes and generates a representation of the outside world is still one of the biggest unknowns in neuroscience today,” says Reynolds, holder of the Fiona and Sanjay Jha Chair in Neuroscience. “Our research provides important insights into how the brain processes borders, which could lead to a better understanding of psychiatric conditions where perception is disrupted, such as in schizophrenia.”

John Reynolds and Tom Franken

From left: John Reynolds and Tom Franken.  Image credit: Salk Institute