VEP, physiological and psychological circadian variations in humans

Area of Science:

• Neuroscience
• Chronobiology
• Human Physiology

Background:

• Circadian rhythms influence various physiological and cognitive functions.
• Visual evoked potentials (VEPs) are electrophysiological measures of visual pathway function.
• Understanding circadian influences on VEPs is crucial for interpreting visual system dynamics.

Purpose of the Study:

• To investigate circadian variations in human visual evoked potentials (VEPs).
• To correlate VEP circadian patterns with other physiological and psychomotor performance measures.
• To explore potential common pacemakers for these daily rhythms.

Main Methods:

• Eight male volunteers underwent testing every 3 hours over a 30-hour period.
• VEPs were elicited using checkerboard pattern reversals.
• Simultaneously assessed: oral temperature, urine output, urinary potassium, grip strength, tapping rate, reaction time, and a letter cancellation test.

Main Results:

• Significant circadian variations were observed in VEP latencies (P100 and N140 components), peaking between 2-5 a.m. and reaching minimums around 5 p.m.
• Pronounced circadian variations were also found in physiological parameters and psychomotor performance.
• Oral temperature showed correlations with most other circadian variables, and VEP latencies exhibited a moderate negative correlation with oral temperature.

Conclusions:

• Human VEPs exhibit significant 24-hour variations, particularly in component latencies.
• These VEP variations are associated with daily rhythms in physiological and performance measures.
• While correlations exist, the data suggest it is premature to confirm a shared pacemaker for all investigated circadian parameters.