Multiunit neural responses to strong finger pulp vibration. II. Comparison with tactile sensory thresholds.

In a companion microneurographic study (Schmidt et al. 1990) maximal multiunit sensory responses to finger pulp vibration were compared with maximal responses evoked by electrical stimulation of the digital nerve. It was found that the MR/ER ratio, i.e. the ratio between the magnitudes of the responses to mechanical and electrical stimulation, decreased with increasing age. The shape of this age-related decline in the ratio corresponded well with the decrease in the number of Meissner corpuscles found in histological studies. In the present study the tactile sensory detection thresholds were measured in the same subjects that participated in the companion study and the relationship between these thresholds and the MR/ER ratios was examined. The tactile sensory detection threshold increased with age. A weak negative correlation was found between the threshold and the ratio. However, after compensation for common age-mediated effects, this negative correlation disappeared. Thus, the results indicate that measurement of tactile sensory detection thresholds and determination of MR/ER ratios may complement each other, giving an indication of different types of derangement of the mechanoreceptive system.