The ability to tactually recognize fine spatial details, such as the raised dots used in braille, is especially important to those who are blind. With that in mind, a team of researchers has identified the neural circuitry that facilitates spatial discrimination through touch. Understanding this circuitry may lead to the creation of sensory-substitution devices, such as tactile maps for the visually impaired.
The findings appear in the Oct. 10 edition of The Journal of Neuroscience.
The research team, led by Krish Sathian, MD, PhD, professor of neurology in Emory University School of Medicine, included first author Randall Stilla, research MRI technologist at Emory, and Gopikrishna Deshpande, Stephen Laconte and Xiaoping Hu of the Coulter Department of Biomedical Engineering at Georgia Tech and Emory.
Using functional magnetic resonance imaging (fMRI), the researchers found heightened neural activity in a network of frontoparietal regions of the brain when people engaged in fine tactile spatial discrimination. Within this network, the levels of activity in two subregions of the right posteromedial parietal cortex--the right posterior intraparietal sulcus (pIPS) and the right precuneus--were predictive of individual participants' tactile sensitivities.
To determine which areas of the brain were involved in identifying fine spatial details, the researchers asked 22 volunteers to determine only by touch whether the central dot of three vertically arranged dots was offset to the left or to the right of the other two.
"Using their right index fingers, the subjects got to feel the dots for one second to determine in which direction the central dot was offset," says Dr. Sathian. "We also varied the amount the dot was offset from the other two, which allowed us to quantify people's sensitivity. In other words, we asked what is the minimal offset required to discriminate."
In a separate control task, the subjects w
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