Double stimulation of tiny skin areas in human subjects increases the number of C- and Adelta-fiber responses.

The stimulation of tiny skin areas has been shown to be a useful method for the investigation of the central nervous processing of C-fiber stimulation. However, recent studies have also indicated that most subjects fail to recognize a large number of such stimulation. This fact renders this method to be rather time consuming, a fact that limits its applicability. To reduce the duration of examination, we here examined the effects of double stimulation of tiny skin areas as compared to the stimulation of tiny skin areas with a single stimulus. The comparison is based on subjects' number of recognized stimuli for single and double stimulation and ratings of stimulus intensity. Double stimulation of tiny skin areas resulted in a significant increase of the number of recognized stimuli as compared to single stimulation. This increase of the number of recognized stimuli is accompanied by an increase of the averaged subjects' experience of stimulus intensity. However, there was no significant increase of intensity rating for the different types of fibers stimulated. Data indicate that the double stimulation of tiny skin areas represents an alternative option to the application of single stimuli to tiny skin areas that significantly reduces the exposure time of subjects in order to evaluate behavioral consequences of the stimulation as well as central nervous processing of C- and Adelta-fiber input.