Analysis of eyeblink activity during discriminative tasks.

To evaluate the blinking pattern during and after cognitive processing, 10 subjects' eyeblinks were recorded by a videotape recording camera placed 100 cm from the subjects' side. The subjects' task was to discriminate two kinds of auditory tones presented serially and to discriminate two kinds of visual stimuli presented serially. Treatments were composed of the baseline condition preexperiment, the visual task with no discrimination, the visual discriminative task, the auditory task with no discrimination, and the auditory discriminative task. The blink rate in each treatment, the temporal distribution of blinks poststimulus, and the blink waveform were evaluated. Although blinks were not inhibited during tasks, frequent blinks after tasks were observed in both modalities. Blinks concentrated between 300 msec. and 800 msec. after the discriminated stimulus and formulated the blink-rate peak. The closing velocity of lid in the blink rate peak was lower after auditory stimulus. Moreover, the lid's opening velocity after the auditory discrimination was higher. These results indicated that the eyelid closed slowly and opened quickly after the auditory discriminative stimulus.