APR 14, 2015 04:26 PM PDT

Touch-Sensing Neurons Are Multitaskers

Two types of touch information - the feel of an object and the position of an animal's limb - have long been thought to flow into the brain via different channels and be integrated in sophisticated processing regions. Now, with help from a specially devised mechanical exoskeleton that positioned monkeys' hands in different postures, Johns Hopkins researchers have challenged that view. In a paper published in the April 22 issue of Neuron, they present evidence that the two types of information are integrated as soon as they reach the brain by sense-processing brain cells once thought to be incapable of such higher-order thought.
To perceive objects we touch, our brains must integrate tactile information with an awareness of the position of our fingers.
Past studies have indicated that the feel of an object against the skin and position information of the hands and fingers were processed separately in the sensory system's first-line sense processors, and then passed along to more sophisticated brain regions to be integrated. But it was a challenge to reliably differentiate brain activity caused by the two inputs from one another and from the brain's commands to muscles, says Manuel Gomez-Ramirez, Ph.D., an assistant research scientist at The Johns Hopkins University. To solve that problem, Steven Hsiao, Gomez-Ramirez's late mentor, and his colleagues developed a machine that positions a monkey's hand and delivers stimuli to its fingers.

In this experiment, then-graduate student Sung Soo Kim, Ph.D., now a research specialist at the Howard Hughes Medical Institute, trained monkeys to perform an unrelated visual task while their hands were manipulated by the machine, which moved their fingers slightly from side to side and up and down at precise angles. The machine also pressed a plastic bar to the monkeys' fingertips in different orientations. By monitoring the monkeys' brains in real time, the research group saw that the position and touch information were conveyed through the same cells in the somatosensory cortex.

"This study changes our understanding of how position and touch signals are combined in the brain," says Gomez-Ramirez. This information could be used in efforts to better integrate prostheses with patients' brains so that they behave more like natural limbs, he notes.

"Holding objects and exploring the world with our hands requires integrating many sensory signals in the brain and continuously supplying this information to motor areas so that it can issue the appropriate commands for holding objects," Gomez-Ramirez says. "Our understanding of how these processes occur is very limited, and Steve Hsiao spent a lot of time thinking about the problem and figuring out how to test it."

The study was funded by the National Institute of Neurological Disorders and Stroke and the Samsung Scholarship Foundation.

Source: Johns Hopkins University
About the Author
  • Ilene Schneider is the owner of Schneider the Writer, a firm that provides communications for health care, high technology and service enterprises. Her specialties include public relations, media relations, advertising, journalistic writing, editing, grant writing and corporate creativity consulting services. Prior to starting her own business in 1985, Ilene was editor of the Cleveland edition of TV Guide, associate editor of School Product News (Penton Publishing) and senior public relations representative at Beckman Instruments, Inc. She was profiled in a book, How to Open and Operate a Home-Based Writing Business and listed in Who's Who of American Women, Who's Who in Advertising and Who's Who in Media and Communications. She was the recipient of the Women in Communications, Inc. Clarion Award in advertising. A graduate of the University of Pennsylvania, Ilene and her family have lived in Irvine, California, since 1978.
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