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New research links size of visual cortex to quality of vision

A team of neuroscientists have discovered they can predict how well someone can see based on the unique structure of their primary visual cortex.

They found the size of the primary visual cortex and the amount of brain tissue dedicated to processing visual information at certain locations of visual space can predict how well someone can see.

Their research, published in the journal Nature Communications, reveals a new link between brain structure and behaviour.

Mr Marc Himmelberg, a postdoctoral researcher in New York University’s Center for Neural Science and Department of Psychology, is the studies’ lead author.

“By showing that individual variation in the structure of the human visual brain is linked to variation in visual functioning, we can better understand what underlies differences in how people perceive and interact with their visual environment,” he said.

Himmelberg and his co-authors, Jonathan Winawer and Marisa Carrasco, professors in NYU’s Center for Neural Science and Department of Psychology, sought to illuminate the relevance of these brain traits to how humans see.

Using functional magnetic resonance imaging (fMRI), the scientists mapped the primary visual cortex (or V1) size of more than two dozen humans. The researchers also measured the quantity of V1 tissue these individuals have dedicated to processing visual information from different locations in their field of view—locations to the left, right, above, and below fixation.

Participants also undertook a task designed to assess the quality of their vision at the same locations in their field of view as the V1 measurements. The participants discriminated among the orientation of patterns shown on a computer screen, which were used to gauge contrast sensitivity.

Their results showed that differences in V1 surface area could predict measurements of people’s contrast sensitivity.

First, people with a large V1 had better overall contrast sensitivity than did those with a small V1 (the largest surface area being 1,776mm2 and the smallest being 832mm2).

Second, people whose V1 had more cortical tissue processing visual information from a specific region in their field of view had higher contrast sensitivity at that region relative to those with less cortical tissue dedicated to the same region.

Third, higher contrast sensitivity at a specific location (eg, left) than at another location equidistant from fixation (eg, above) corresponded to regions with more or less cortical tissue, respectively.

“In sum, the more local V1 surface area dedicated to encoding a specific location, the better the vision at that location,” Carrasco said.

“Our findings show differences in visual perception are inextricably linked to differences in the structure of the primary visual cortex in the brain.”

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