Nerve conduction in general is an electro-chemical  event; conduction of pain therefore also is of such a nature until it meets certain structures within the brain (basal ganglia). It may be modified or influenced not only by pharmacological (i.e. drugs) but also by electrical means. After the algophorus impulses meet certain cerebral areas, we sense “pain”, just as certain other impulses turn to our sensing of light, sound, touch etc. in other areas of the brain. To influence our pain sensation would seem to be most effectively and very simply done by interrupting the pathways along which these electrochemical events run centripetally. This applies especially if the cause of pain may not be visualized and may not be removed. The relative strength or degree of any sensation is made aware to us by a very special way of coding of these events. The main advantage of this system of coding by modulation of pulse density is that the information contained in a single spike (action potential) may vary by 500% and drop to as low as 20% of the original size without losing any information; information which is made available in the next proximal synapse, or the last end of the pathway within the cerebral cortex just as well, by decoding. The sensation of “weak pain” is caused by just a few “spikes” of action potentials running centripetally over the pathways, while “stronger pain” is indicated to us by a greater number of spikes per sec. arriving in the brain from the periphery. This may be demonstrated very impressively for the sensation of temperature (fig. 1). By this experiment one may determine objectively the strength of a sensation (or pain) or — expressed in a different way, if a sensation of pain is increasing (in this case, the frequency of spikes is increasing) or decreasing (then frequency of spikes would be decreasing).
KeywordsSensory Modality Nerve Block Spike Frequency Stimulus Strength Sympathetic Fiber
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