Primates are known to have a remarkable ability to place visual stimuli into familiar and meaningful categories, such as fruit or vegetables. They can also direct their spatial attention to different locations in a scene and make spatially-targeted movements, such as reaching.
The study, published in the March issue of Neuron, shows that these very different types of information can be simultaneously encoded within the posterior parietal cortex. The research brings scientists a step closer to understanding how the brain interprets visual stimuli and solves complex tasks.
"We found that multiple functions can be mapped onto a particular region of the brain and even onto individual brain cells in that region," said study author David Freedman, PhD, assistant professor of neurobiology at the University of Chicago. "These functions overlap. This particular brain area, even its individual neurons, can independently encode both spatial and cognitive signals."
Freedman studies the effects of learning on the brain and how information is stored in short-term memory, with a focus on the areas that process visual stimuli. To examine this phenomenon, he has taught monkeys to play a simple video game in which they learn to assign moving visual patterns into categories.
"The task is a bit like a baseball umpire calling balls and strikes," he said, "since the monkeys have to sort the various motion patterns into two groups, or categories."
The monkeys master the tasks over a few weeks of training. Once they do, the researchers record electrical signals from parietal lobe neurons while the subjects perform the categorization task. By measuring electrical activity patterns of these neurons, the researchers can decode the information conveyed by the neurons' activity.
"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 information—multiplexing 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 category-based decision-making tasks."
What does the brain gain from this territorial arrangement?
"There has long been a tendency to look at the many distinct anatomical areas of the cerebral cortex of the brain and to assume that each area is like a specialized module that plays a very specific function." Freedman said. "Our results support the growing sense that most, if not all, of these brain areas have multiple overlapping roles."
A brain that includes such overlapping functional centers may be more efficient, Freedman suggests. "It makes mapping these regions more complicated for scientists like us, but it may boost the brain's capacity. If each area can do a number of different things, you can squeeze a lot more function into the same space."
A next step is to understand how neuronal category representations develop in LIP neurons during the learning process, the authors said.
The paper, "Independent category and spatial encoding in parietal cortex," will be published online March 6 by the journal Neuron. The National Institutes of Health funded this study with additional support from the National Science Foundation, the McKnight Endowment Fund for Neuroscience, the Alfred P. Sloan Foundation and the Brain Research Foundation. Gang Huang, formerly a research technician in the lab, also contributed to the research.
John Easton | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences