WASHINGTON, D.C. December 3 -- New animal research shows that sensory deprivation not only influences the sensory brain areas, but surprisingly also stifles the development and organization of areas involved in the control of voluntary movement. And the effects are particularly drastic in early life.
"The research suggests that sensory feedback to the brain's motor cortex system is one of the major driving forces that shapes motor function during development," says the study's author, George Huntley of The Mount Sinai School of Medicine in New York. "The discovery also suggests that early in development there is a restricted time period where the motor system is most susceptible to modification and refinement by incoming sensory signals."
"The human implications could be that visual defects early in life may affect not only the sensory brain areas that process vision, but also the motor cortex areas that mediate visually-guided motor coordination," he says.
Huntley's study, primarily funded by the National Institutes of Health, is published in the December 1 issue of The Journal of Neuroscience.
"The study reinforces the view that our children require sensory and motor experiences during development," says Jon Kaas, a sensory systems expert at Vanderbilt University in Nashville. "While deprivation is harmful, supernormal sensory and motor conditions may lead to supernormal individuals."
In the study, Huntley tested the effects of a form of sensory deprivation by trimming the whiskers on rats. This made the animals experience abnormal sensory inputs to sensory and motor areas of the cerebral cortex. Rats use the whiskers on their snouts like humans use their fingertips to explore and discriminate surface features such as texture. Whiskers function through motor areas of the brain including the motor cortex, which sweep them back and forth and the somatosensory cortex, which processes the retrieved information. Huntley examined a group of adult rats that had the whiskers on one side of their snout trimmed starting at birth and another group that had their whiskers trimmed starting in adulthood.
A stimulating electrode implanted in the animals' motor cortex revealed representations of motor activity. "Study results show significantly smaller representations of motor activity and some abnormal motor activity patterns in the rats that were trimmed at birth," says Huntley. "The adult-trimmed group had no significant changes in the size of their representations of motor activity maps, but they did show some slight changes in the form of motor activity elicited."
In future studies, the researchers plan to investigate the mechanisms that underlie the changes in the motor cortex.
Huntley is a member of the Society for Neuroscience, an organization of more than 27,000 basic scientists and clinicians who study the brain and nervous system. The Society publishes The Journal of Neuroscience.