ELECTRICAL-STIMULATION OF A FOREPAW DIGIT INCREASES THE PHYSIOLOGICALREPRESENTATION 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 sti mulation (1.5x threshold for 2 h) of the glabrous tip of D3 in anesthe tized animals (n = 6). Measurements of D3 representation were also mad e in anesthetized non-stimulated control animals (n = 2). The post-sti mulation areal measurements of D3 representation in experimental anima ls were statistically significantly larger than both pre-stimulation m easurements in experimental animals and post-stimulation measurements in control animals. Our results suggest that short-term electrical sti mulation 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 ane sthetized animals suggests that the results are independent of the sta te of the animal. The present findings emphasize the importance of aff erent input in modulating cortical organization.