Part of the brain of mammals is organized into areas that are primary regions for processing sensory input. The somatosensory cortex is an area where different parts of the body are represented in different subareas, all showing an orderly spatial mapping of the peripheral inputs. The area of cortex which shows a response when a particular fingertip is touched, for example, is termed the "representation" for that fingertip, and nearby are the representations for the rest of that finger, and for the other fingers, the hand, and so on. The discovery some years ago that these maps were not determined during development alone, but could change during adult life as a result of loss of a digit or other deprivation, was revolutionary. This project adds two novel aspects to the progress in this field. First, it raises the issue that sensory experience changes the organization of adult sensory cortex even when the experience represents only a small part of the animal's total daily experience. Second, the approach adds a paradigm of enhanced sensory stimulation, rather than just deprivation, to drive the changes in cortical organization. In the rodent somatosensory cortex are distinctive aggregations of cell clusters, called barrels. This anatomical feature provides an excellent model system for studying details of morphological changes that accompany physiological changes, and correlation of these changes at the cellular level clarifies what mechanisms may be involved in the plasticity of the functional maps. Tactile deprivation or stimulation of the forepaw in trained rats will be used to define the sensory experience, and see how the cortical maps change with change in experience. Results will be important for understanding the effects of use and disuse in the nervous system, refining models of cortical plasticity, and for understanding the fundamental role of experience in learning.
