Diurnal variations in auditory & visual reaction time in young adults

Reaction time is an indirect measure of processing capability of central nervous system and simple means of determining sensory motor association performance of an individual. The present study was conducted to see the diurnal variation of visual and auditory reaction time. The present study was carried out on 50 asymptomatic medical students of 18-25 years of age of both sexes. Auditory reaction time (ART) with low and high frequency stimulus & visual reaction time (VRT) to red and green light stimuli were measured twice a day at 7 A.M. & 7 P.M. with multiple choice electronic apparatus. The study showed VRT for red colour stimulus is 133.54 +/- 68.64 in morning & 161.86 +/- 37.48 in evening and the same for green colour stimulus are 161.92 +/- 45.25 in morning & 186.92 +/- 47.38 in evening respectively in all subjects. Their difference was statistically significant (P < 0.001). The study showed ART for low frequency sound is 124.48 +/- 31.11 in morning & 153.3 +/- 35.69 in evening and the same for high frequency sound is 160.76 +/- 87.68 in moming & 184.86 +/- 51.62 in evening respectively in all subjects. Their difference was statistically significant (P < 0.001). Since reaction provides a quantitative and physical measure of mental events, the increase in visual & auditory reaction times in the evening could be attributed to the modulation of neurotransmitters and processing capability of the central nervous system as the day advances.