A study in monkeys finds many neurons fire in response to more than one aspect of an object
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Some nerve cells in the brain are multitaskers, responding to both color and shape, a survey of over 4,000 neurons in the visual systems of macaque monkeys finds.
The finding, described in the June 28 Science, counters earlier ideas that vision cells nestled in the back of the brain each handle information about only one aspect of sight: an object’s color or its orientation, an element of shape. Some scientists had thought that those aspects were then put together by other brain cells in later stages of visual processing to form a more complete picture of the world.
In the new experiment, four macaques looked at a series of sights made of moving lines on a screen. Each time, the lines were one of 12 possible colors and moved at particular angles, creating an effect similar to a spinning candy cane in two dimensions.
Using genetic tricks that made nerve cells glow when active, the researchers watched for action among the monkeys’ cells in an area of the brain that handles vision. Called V1, this stretch at the back of the brain is one of the first areas to interpret sight signals. Most of the cells that had a favorite color, indicated by their activity, also had a favorite orientation of lines, the researchers found. “Thus, textbook models of primate V1 must be updated,” the team writes.
PUTTING IT TOGETHER This video captures nerve cells in a monkey’s visual system firing off signals. Some of these cells respond both to a favorite color and favorite shape. The discovery counters previous ideas that information about color is processed separately from information about shape in the brain.
A.K. Garg et al. Color and orientation are jointly coded and spatially organized in primate primary visual cortex. Science. Vol. 364, June 28, 2019, p. 1275. doi:10.1126/science.aaw5868.
L. Sanders. Babies categorize colors the same way adults do. Science News Online, June 1, 2017.