The electrically elicited R2 blink reflex consists of distinct subcomponents

In previous studies the later parts of the electrically evoked R2 blink reflex has been found to be more susceptible to the inhibitory effects of repetitive stimulation and prepulses. Consequently, it has been suggested that the R2 reflex may be composed of distinct subcomponents. However, as of yet, no study revealed electromyographical evidence for this hypothesis, probably due to a putative temporal overlap that makes it difficult to clearly separate distinct R2 subcomponents. In the present study we investigated the electrically evoked blink reflex in 26 healthy volunteers by using the paradigm of self-stimulation, which has been found to inhibit the R2 and may thus help to differentiate putative R2 subcomponents. In most of the participants self-stimulation resulted in inhibition of the reflex involving predominantly later sections of R2. In addition, in three subjects it was possible to clearly separate distinct R2 subcomponents. These findings suggest that the electrically elicited R2 blink reflex--like the acoustic blink response--consists of superimposed distinct subcomponents. Based on their differential modulation evoked by habituation, pre-stimulation and self-elicitation it is hypothesized that the early portions of the R2 represent the electrically evoked blink reflex, whereas the later sections belong to the generalized startle reaction in man. However, due to their temporal overlap a differentiation might not be possible in conventional recordings.