Electrical stimulation of a forepaw digit increases the physiological representation of that digit in layer IV of SI cortex in rat

WE studied the physiological representation of digit three (D3) in rat somatosensory cortex (SI) before and immediately after electrical stimulation (1.5x threshold for 2 h) of the glabrous tip of D3 in anesthetized animals (n = 6). Measurements of D3 representation were also made in anesthetized non-stimulated control animals (n = 2). The post-stimulation areal measurements of D3 representation in experimental animals were statistically significantly larger than both pre-stimulation measurements in experimental animals and post-stimulation measurements in control animals. Our results suggest that short-term electrical stimulation is sufficient to expand the D3 representation in each of the experimental animals, while the maps in non-stimulated controls showed little variation. The fact that these studies were carried out in anesthetized animals suggests that the results are independent of the state of the animal. The present findings emphasize the importance of afferent input in modulating cortical organization.