An intact peripheral nerve preparation for examining the central actions of single kinaesthetic afferent fibres arising in the wrist joint of the cat

Abstract

Intraneural microstimulation of single tactile or kinaesthetic afferent fibres arising in the hand of conscious human subjects has revealed marked differences among the different classes in their capacity to generate a perceptual response. In order to test the hypothesis that these different capacities might reflect a differential security in the transmission of singnals across synaptic junctions in the dorsal column nuclei or other levels of the somatosensory pathway we have previously developed a paired, simultaneous recording paradigm in the cat to analyze transmission characteristics within the dorsal column nuclei for single identified tactile and muscle sensory fibres of the forearm. These studies have depended upon the use of a fine peripheral nerve or nerve fascicle preparation in which it is possible to monitor the activity of single sensory fibres while the nerve remains in continuity with the central nervous system. Although we have previously described a preparation that allows the activity of single joint afferent fibres from the hindlimb to be monitored in the intact medial articular nerve, these hindlimb kinaesthetic afferents fail to project directly to the dorsal column nuclei. In the present study we report a forearm nerve preparation in the cat that permits the simultaneous recording of activity from individual wrist joint afferent fibres and their target neurones of the dorsal column nuclei. When this nerve is freed from nearby tissue over a distance of 2-4 cm and left in continuity, it is possible with a silver hook electrode to monitor the impulse activity of each group II joint afferent fibre with an excellent signal-to-noise ratio. The preparation should prove ideal for examining the central actions and security of transmission across the dorsal column nuclei for single, identified joint afferent fibres of the forearm.