The right side of the brain is more involved in spatial processing tasks, even when it was the same side of the brain that feels stimuli. This was in contrast to the general belief that the left side of the brain controls the right side of the body.

A team of scientists have identified the exact parts of the brain involved in spatial discrimination. The work will aid in creation of sensory-substitution devices, such as tactile maps for the visually impaired.
Using three dots with a central dot slightly offset to one side, in varying degrees, and later in a temporal task to determine how long the subjects were touched by three dots, the scientists contrasted the brain activity and area.

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 and others at the Coulter Department of Biomedical Engineering at Georgia Institute of Technology and Emory University in Atlanta.

“More and more we are finding that the right side of the brain is particularly important in many types of sensory processing,” said Dr Sathian, adding that in general the left side of the brain controls the right side of the body.
Dr Sathian’s and Dr Hu’s laboratories also collaborated to determine the strength and direction of the connections between the areas of the brain that govern tactile spatial acuity (perception).

“We found that there are two pathways into the right posteromedial cortex that not only predict individuals’ acuity but also predict the magnitude of neural activation," said Dr Gopikrishna Deshpande, who performed the connectivity analyses. "In better performers, the paths predicting acuity converge from the left somatosensory cortex and right frontal eye field (an attentional control centre), onto the right pIPS (posterior intraparietal sulcus). These paths are stronger during spatial than temporal discrimination.”

The researchers are not yet sure why this particular neural pathway exists. Dr Sathian suggests the signal patterns may be a combination of attentional, tactile, and visual processing reflecting the visualisation of the spatial configurations.

Future research, he says, will attempt to unravel the mechanisms underlying these different component processes. This study was funded by grants from the National Institutes of Health.