Human pupillary light reflex and reaction time at different intensity of light stimulation (a simple motor reaction to modify the human pupillogram).

The relations between the parameters of a pupillary light reflex and the reaction time to four intensities of light stimulation were studied in 13 normal volunteers (mean age 21.7 years). The consensual pupillary reactions to light were recorded at an infrared-reflecting pupillograph; the reaction time (RT) was recorded by a button pressed with the thumb. All subjects were tested at least twice in two blocks of trials: NO-RT-block, where only pupillograms (PGs) were recorded; and RT-block, where simple motor reactions were performed and recorded on a tape simultaneously with PGs. It was demonstrated that: (1) the intensity of light stimulation is a principal factor influencing the parameters of the human PG and is not a principal factor influencing the visuo-motor reaction time; and (2) A simple motor reaction exerts an inhibitory effect on the PG-amplitude and latency and on other PG-parameters. Some implications of probable mechanisms of the inhibitory influence of RT-processing on the PG-parameters are discussed.