The differentiation of axonal and soma-dendritic spike activity
- Cite this article as:
- Fussey, I.F., Kidd, C. & Whitwam, J.G. Pflugers Arch. (1970) 321: 283. doi:10.1007/BF00588643
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Experiments were performed to examine the usefulness of mean spike duration measurements as a means of distinguishing between axonal and soma-dendritic activity recorded from the C.N.S. by glass insulated platinum microelectrodes. Units recorded from cat gracile and cuneate nuclei were separated into presynaptic and postsynaptic groups on the basis of: a) the maximum number of spikes evoked from a single electrical stimulus to the skin receptor area; b) the maximum frequency at which evoked spikes would follow every stimulus; c) the variability of latency at threshold stimulus intensity; d) the decrement of this variability upon increasing the intensity; e) the reduction of mean latency upon increasing stimulus intensity above threshold. Fifteen presynaptic units were recorded, all of which had short mean spike durations. Of the 41 postsynaptic units 5 exhibited short mean spike durations in the range associated with presynaptic units and were consequently classed as postsynaptic axons. The remaining postsynaptic units had long mean spike durations. On the basis of mean spike duration alone no presynaptic (i.e. primary afferent fibre) unit would have been erroneously classified as a postsynaptic (soma-dendritic) unit.