Circadian misalignment impairs ability to suppress visual distractions

Evening-type individuals often perform poorly in the morning because of a mismatch between internal circadian time and external social time, a condition recognized as social jetlag. Performance impairments near the morning circadian (~24h) trough have been attributed to deficits in attention, but the nature of the impairment is unknown. Using electrophysiological indices of attentional selection (N2pc) and suppression (P_D) we show that evening-type individuals have a specific disability in suppressing irrelevant visual distractions. More specifically, evening-type individuals managed to suppress a salient distractor in an afternoon testing session, as evidenced by a P_D, but were less able to suppress the distractor in a morning testing session, as evidenced by an attenuated P_D and a concomitant distractor-elicited N2pc. Morning chronotypes, who were well past their circadian trough at the time of testing, did not show this deficit at either test time. These results indicate that failure to filter out irrelevant stimuli at an early stage of perceptual processing contributes to impaired cognitive functioning at non-optimal times of day, and may underlie real-world performance impairments, such as distracted driving, that have been associated with circadian mismatch.