To quantify changes in tactile acuity, the researchers dropped the distance between two pins pressing against human skin. At some distance, people can no longer detect two distinct pressure points on the tips of their index fingers.
Monitoring changes in the minimum distance that still allows for two-point detection provides a measure of tactile acuity and perceptual learning.
Dinse explained that the cortex of the human brain has both a sensory and a motor "body map." Using these maps unconsciously, humans navigate through the physical world.
"We are now finding ways to interact with the brain's body maps. This has enormous power," said Dinse who explained that manipulating body maps housed in the brain can have an immediate impact on behavior and perception.
The brain modifies its body maps as a basic tool for learning and adapting to new situations. This disconnecting and reconnecting of neurons is known as synaptic plasticity.
In an attempt to alter their sensory body maps, participants wore an eight millimeter disc for three hours that stimulated a patch of skin on tips of their right index fingers. This coactivation boosts the number of neurons involved in processing tactile information coming from the area of stimulated skin. By this method, external stimulation to finger tips temporarily reorganized part of the cortex and modified the sensory body maps of the participants.
After 24 hours, the enhanced ability to detect pin points dropped to normal levels. Dinse noted that further coactivation of the same area quickly reestablished the heightened tactile acuity. With the goal of rehabilitation treatments in mind, Dinse is currently looking for ways to make the improved sensory reception more durable and long lasting.
The coactivation protocol described in this study requires no active participation by the participant and this makes it an attractive therapeutic approach, according to Dinse.
Contact: Daniel Kane
dkane@aaas.org
202-326-6634
American Association for the Advancement of Science
3-Jul-2003