Circadian rhythms in two components of executive functions: cognitive inhibition and flexibility

The objective of this study was to analyze possible circadian variations in two components of executive functions: inhibition and flexibility. Participants were eight undergraduate students, age: 17.75 ± 0.46 years, one male and seven female. They were kept in a constant routine protocol for 29 h. Rectal temperature was recorded every minute and responses to a computerized Stroop-like task with shifting criteria were recorded every 100 min. The task had three sections: match, no-match (index of inhibition), and shifting criteria (index of flexibility). There were circadian variations in rectal temperature, inhibition and flexibility. These cognitive processes showed a 1–2 h phase delay with respect to rectal temperature, and were modulated by sustained attention (time on task). The decline of these components of executive functions at night and in the early morning impairs decision-making and problem-solving, thus promoting errors while driving a car or working at night.