Causes of the instability of R3 component of electrically evoked blink reflex: role of the attention to the stimulus.

The causes of the spontaneous sharp amplitude variations of R3 component of electrically evoked blink reflex have been analyzed, in 10 subjects 24-30 years, in different experimental conditions: a) neutral condition, b) selective attention to the stimulus; distraction from the stimulus: c) by looking at a poster rich with images and d) by signaling from sequences of numbers three targets. In the situations where the subject does not play attention to the experimental set up, (a), or is distracted from it (c), the R3 response shows the maximal amplitude, whereas in condition of greater attention to the stimulus (b), R3 appears sharply reduced in amplitude. Where attentive levels are high but not focused on the stimulus (d), the reduction of the third reflex response is lesser. The reciprocal modifications with respect to the other responses R1 and R2 are also discussed.