Showing papers in "Journal of Neurophysiology in 1943"

Neuron patterns controlling transmission of ipsilateral hind limb reflexes in cat

Abstract: THE SEGMENTAL REFLEX discharge (7,31,21) must be considered of anatomical rather than functional significance in that it contains, in unnatural combination , those elements which constitute the several distinct ipsilateral reflexes. In the present paper are the results of experiments designed to resolve the segmental reflex into its functional components. The observation that a major division of the segmental reflex into its direct (two-neuron-arc) and indirect (multineuron-arc) components followed segregation of muscle afferent and cutaneous afferent fibers for afferent stimulation (21) provides the point of departure for the experiments to be described. Some of the present observations have been mentioned briefly in a preliminary note (23). A general discussion of these and other results will be found in another paper (25). The afferent fibers of the A group (14) exhibit a range of diameters extending from 20~ to 1.5~ (36). In a dorsal root the whole range of fibers is present, but in the peripheral nerves significant segregation .s are found (36, 8, 29, 14) which permit a degree of selective stimulation of the various components (21). For the purposes of the present discussion the afferent fibers will be classified into groups, each group being marked by a peak in the fiber distribution plots of one or another of the several peripheral nerves. Group I consists of the largest afferent fibers, which are to be found only among the afferent fibers arising from muscle. Approximately these fibers range from 20~ to 12~ in diameter (8, 29), with a distribution peak at 15 to 16~. Group II contains fibers of approximately 12~ to 6~ in diameter, with a mode at 8 to 9p. These fibers form a prominent peak in the fiber distribution plots of cutaneous nerves (8, 30, 14), but they are poorly represented among the muscles afferent fibers (8, 29). Group III consists of fibers gathered about a peak at 3 to 4~ (the delta pile). These last are to be found in both muscle and cutaneous nerves. Another category, to consist of the C fibers, the afferent and reflex function of which is proven (3, 2), should be included as group IV. These fibers have not been studied during the course of the present experiments. Since group I and group II fibers are the lowest threshold fibers in muscle and cutaneous nerves respectively, they may be excited in isolation by the simple expedient of selecting the appropriate nerves …

The response of single auditory-nerve fibers to acoustic stimulation

Abstract: THE AIM OF the experiments described here was to study the response of single auditory-nerve fibers to acoustic stimulation delivered to the intact ear. Similar studies on other single afferent fibers have remarkably extended knowledge of the mode of action of diverse sensory mechanisms, while at the same time emphasizing their fundamental similarities. The present report describes the behavior of single auditory fibers and stresses similarities to other sensory nerves; in a subsequent paper we hope to relate these findings to a specific theory of action of the mammalian cochlea. METHOD Young cats anesthetized with dial (0.75 cc. per kilo) were used in these experiments. The postero-dorsal aspect of the auditory nerve was exposed by removing the lateral portion of the occipital bone where it meets the petrous bone. Bleeding from the sinus petrosus inferior was stopped by judicious cauterization or by Clotting Globulin. * A Ringer-filled glass micropipette with Ag-AgCl wire inserted as close as possible to the tip served as the active lead from the nerve. It was early established that pipettes with openings greater than 5~ do not allow isolation of the action potentials of single auditory fibers. The 3 to 5~ electrodes used have an impedance of about 1 megohm when tested on a resistance-capacity bridge between 0.6 and 2.5 kc. The microelectrode and the indifferent electrode (a silver plate in the neck muscles) led to a capacity-coupled amplifier (Grass) with an input done photographically