ORGANIZATION OF TACTILE DERMATOMES IN CAT AND MONKEY

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Abstract
The evoked potential technic was used to investigate functional organization of the dorsal root in cat and monkey. Afferent stimuli were initiated, and cutaneous tactile fields mapped, by focal movement of body hairs. The skin fields of lumbosacral dorsal root filaments were found to be arranged in orderly, consecutive fashion within the dermatome. Dorsal rootlets innervated skin in a serial overlapping order. The shifting overlap between successive filaments within the dermatome resembled closely the shifting overlap noted by previous investigators between adjacent whole dermatomes. If filaments failed to show responses to movements of hairs, electrical activity could usually be elicited by manipulation of the joints or muscles of the ipsilateral hind limb. There was evidence that certain filaments critained mainly afferents subserving touch, and some seemed to be composed solely of fibers afferent from muscles and joints. The intensity of responses elicited by hair movement usually varied inversely to that obtained by various manipulations of the limb. Dermatomes were outlined for dorsal roots from L-4 to S-4 in the cat, and from L-4 to S-2 in the monkey.