LAUSR

The ability to remember the face and name of a person we have recently met is a critical skill often impacted by cognitive impairment and Alzheimer’s disease. We used a forced desynchrony protocol to explore whether recall of recently-learned face-name pairs is affected by time awake and/or circadian phase in healthy adults. 13 healthy, cognitively normal adults (20-70yrs; 7F) participated in a 39-day inpatient protocol with 3 baseline days (10h time-in-bed/24h) and a 3-week forced desynchrony (FD) segment, where they lived on a 28-h day with sleep restriction (6.5h time-in-bed/28h, equivalent to 5.6h/24h). Core body temperature was collected throughout to estimate circadian period and phase. The face-name test was administered every 4h, beginning 3h after wake. Each test included a learning session with 6 novel face-name pairs. Recall was tested 2h later, when each face was presented twice in random order, once with a correct and once with an incorrect name. Participants were asked to respond whether each face-name pair was correct. Data were averaged across 4-h circadian phase or time awake bins and normalized as a percentage of each participant’s baseline performance. Face-name recall varied by time awake (p<0.05), with performance deteriorating ~12% over the course of 12h of wakefulness. Face-name recall also varied by circadian phase (p<0.05), with a ~10% difference in recall performance from the peak at circadian phase 240° (corresponding to the early biological evening) to the nadir at circadian phase 60° (corresponding to the early biological morning). Both duration of prior wake and biological time of day impact the ability to correctly recall face-name pairs. Under normal entrained conditions, opposing circadian- and wake- dependent effects on memory for face-name associations may interact to produce stable performance across the day. Study supported by P01 AG009975 and conducted at Brigham and Women’s Hospital Center for Clinical Investigation, part of Harvard Clinical and Translational Science Center supported by UL1 TR001102. Authors supported by T32HL007901 and F32HL143893 (RKY); fellowships from the Novartis Foundation, the W.&T. La-Roche Foundation, and Jazz Pharmaceuticals (MYM); a fellowship from the Natural Sciences and Engineering Research Council of Canada (SWC).