MICROELECTRODE STUDIES ON SENSORY AFFERENTS IN THE POSTERIOR FUNICULUS OF CAT

Utilizing a silver microelectrode of5-10μE in diameter insulated by a glass coating, impulse discharges subsequent to adequate stimuli on various parts of the body were recorded from the cervical posterior funiculus of cat and their arrangement was studied. Conclusions are as follows: 1) Responses were obtained ipsilaterally and the forms of spikes could be classified into two types. One is thought to be related to nerve fibre and the other to nerve cell. 2) Responses to touch on the skin or hairs were most frequently obtained. In them, the amplitude of spikes was generally large and adaptation was very quick. Receptive areas for them were fairly localized, particularly restricted on the distal ends of limbs. 3) Impulse discharges responding-to push or pull of the skin were tonic, adapting slowly. The physiological function of these afferents may be partly proprioceptive. 4) Among proprioceptive afferents, which generally adapted slowly, those for muscles were far less frequently encountered than those for articular capsules or tendons. 5) In Goll's funiculus, responses from tactile afferents were far more frequently obtained than those from proprioceptive afferents. The circumstances were quite opposite in regard to Burdach's funiculus. The majority of responses from the thoracic level seems to be concerned with respiratory movements of the chest. 6) From a localized superficial portion of Goll's funiculus closely adjacent to the septum medianum, slowly adapting impulse discharges were obtained subsequent to filling the urinary bladder. Their spike apperances were far smaller than those for tactile afferents. 7) The medio-lateral arrangement, upon the transverse section of the second cervical cord, of those parts of the body from which the responses were obtained was as follows:(a) urinary bladder, (b) tail or perineum, (c) toes of hind limbs, (d) distal half of hind limbs except toes, (e) proximal half of hind limbs, (f) loins or abdomen, (g) chest, (h) toes of fore limbs, (i) distal half of fore limbs except toes, (j) proximal half of fore limbs. 8) Spontaneous impulse discharges, which were obscure in their receptive fields, were frequently recorded in the lateral half of Burdach's funiculus and in an area between Goll's and Burdach's funiculus. They are assumed to be related to slowly adapting afferents and to be proprioceptive in nature.