Analysis of activity in A and C fibres under mechanical and thermal stimulation of the skin receptor field.

Publisher Summary This chapter discusses the analysis of activity in A and C fibres under mechanical and thermal stimulation of the skin receptor field. Under natural conditions, external stimulation causes excitation of a great number of receptors of various kinds. The impulse flow from receptors varies on various stimuli affecting the skin. This difference is perhaps the reason for the determination of sensation modality by the central nervous system. For determination of quantitative characteristics of the total afferent flow under various externally applied stimuli, methods that permit quantitative analysis of afferent impulses in all nerve fibres simultaneously should be used. The chapter presents the modified method of colliding impulses, which permitted the determination of not only the relative number of active fibres but also the frequency spectrum of orthodromic flow in these fibres as well. The principle of modification lies in a gradual increase of antidromic stimulation frequency that results in ortho- and antidromic impulse collisions being forced out from the interelectrode section of the nerve in the fibres where orthodromic frequency is less than the antidromic one. The recorded antidromic potential increases. There have been established certain limitations of the modifications and discrepancies in absolute values of afferent frequencies in comparison with the results obtained by recording the potentials from a single fibre.