P252 Prepulse inhibition of blink reflex after different types of somatosensory stimuli

Abstract

Objective Prepulse inhibition (PPI) is a neurophysiological method in which inhibition of a reflex response occurs when a preceding stimulus is applied. It is generally created by digital somatosensory stimulation. R2 magnitude gets reduced using certain interstimulus intervals (ISIs) whereas short ISI leads to facilitation of R1. We aimed to analyze the changes of BR-PPI using digital somatosensory stimulation and mixed nerve stimulation at wrist. Patients and method We included 18 healthy subjects (38.8 ± 10.9 years, 12 women) and performed BR investigations after unconditioned and conditioned supraorbital electrical stimuli. For conditioned stimuli, we applied two different preceding subthreshold somatosensory stimuli: i. stimulation of second finger, ii. stimulation of median nerve at wrist. Three different ISIs (50, 100, 300 ms) were used for each type of stimulation. Presence and extent of alteration after each conditioning stimulus were compared. Results R2 area significantly reduced after each conditioning stimulus at each ISI. R2 latency was longer at ISIs of 100 and 300 ms whereas R1 magnitude was higher at all ISIs. However, the increase in R1 magnitude was more pronounced at ISIs of 50 and 100 ms. Conclusions Our results clearly show that both digital somatosensory and mixed nerve stimulations lead to inhibition of R2 area and facilitation of R1 magnitude. Therefore, both stimulations and both techniques are comparable.