"The activity patterns in these parietal neurons carry strong information about the category that each motion pattern gets assigned to during the task," Freedman said.
Over the years, his team's work on categorization has zeroed in on the lateral intraparietal (LIP) area. Studies have shown that this area is vital to directing spatial attention and eye movements. But it had been unclear how an area involved in spatial attention and eye movements could also play a role in non-spatial functions such as visual categorization.
To compare spatial and category functions in the parietal lobe, Freedman and his team added a twist to the monkeys' task. During the category task, the researchers required the subjects to make eye-movements to visual cues at various positions on the computer screen, but the subjects still had to categorize the visual patterns at the same time that they made these eye movements.
Since this parietal brain area is known to be involved in eye movements, the eye movements could have disrupted category information in that part of the brain. Instead, parietal brain cells showed a simultaneous and independent encoding of both eye-movement and category informationmultiplexing of information at the level of single brain cells.
"These signals rode right on top of the eye-movement signals," said the study's first author, Chris Rishel, PhD, a recent graduate from Freedman's laboratory. "We could decode both the eye-movement and the category signals with high accuracy. This tells us that different kinds of information that are usually considered quite unrelated were simultaneously and independently represented by neurons in this particular brain area."
Their results, the study authors note, "support the possibility that LIP plays a key role in transforming visual signals in earlier sensory areas into abstract category signals during cat
|Contact: John Easton|
University of Chicago Medical Center