Afferent pathways of a tactile conditioned reflex after cortical somatosensory ablations

Abstract

Abstract The retention of a tactile conditioned reflex after transection of two spinal pathways, separately or together, was studied in dogs with S I and S II previously removed uni- or bilaterally. Impairment of the reflex was observed in 1 3 cases after transection of the spinocervical tract but in no case after transection of the dorsal columns. Transection of the dorsal columns secondarily to a unilateral transection of the spinocervical tract, or vice versa, invariably caused major impairment of the reflexes from the side where both pathways were transected. It is concluded that the two pathways, exclusively of subserving rapid projection to S I and S II, may transmit activity elicited by the tactile conditioned stimulus to other central nervous structures of importance for the conditioned reflex. The results are discussed in relation to recent findings regarding thalamic connections of the two pathways.