title: The cortisol awakening response is associated with performance of a serial sequence reaction time task.
abstract: There is emerging evidence of a relationship between the cortisol awakening response (CAR) and the neural mechanisms underlying learning and memory. The aim of this study was to determine whether the CAR is associated with acquisition, retention and overnight consolidation or improvement of a serial sequence reaction time task. Salivary samples were collected at 0, 15, 30 and 45 min after awakening in 39 healthy adults on 2 consecutive days. The serial sequence reaction time task was repeated each afternoon. Participants completed the perceived stress scale and provided salivary samples prior to testing for cortisol assessment. While the magnitude of the CAR (Z score) was not associated with either baseline performance or the timed improvement during task acquisition of the serial sequence task, a positive correlation was observed with reaction times during the stable performance phase on day 1 (r=0.373, p=0.019). Residuals derived from the relationship between baseline and stable phase reaction times on day 1 were used as a surrogate for the degree of learning: these residuals were also correlated with the CAR mean increase on day 1 (r=0.357, p=0.048). Task performance on day 2 was not associated with the CAR obtained on this same day. No association was observed between the perceived stress score, cortisol at testing or task performance. These data indicate that a smaller CAR in healthy adults is associated with a greater degree of learning and faster performance of a serial sequence reaction time task. These results support recognition of the CAR as an important factor contributing to cognitive performance throughout the day.
authors.affiliation: The Robinson Research Institute, School of Medicine, University of Adelaide, Adelaide, SA, Australia; Neonatal Medicine, Women's and Children's Hospital, Adelaide, SA, Australia. Electronic address: nicolette.hodyl@adelaide.edu.au.
authors.forename: Nicolette A
authors.initials: NA
authors.lastname: Hodyl
authors.affiliation: The Robinson Research Institute, School of Medicine, University of Adelaide, Adelaide, SA, Australia.
authors.forename: Luke
authors.initials: L
authors.lastname: Schneider
authors.affiliation: The Robinson Research Institute, School of Medicine, University of Adelaide, Adelaide, SA, Australia.
authors.forename: Ann-Maree
authors.initials: AM
authors.lastname: Vallence
authors.affiliation: Department of Psychology, University of Westminster, London, UK.
authors.forename: Angela
authors.initials: A
authors.lastname: Clow
authors.affiliation: The Robinson Research Institute, School of Medicine, University of Adelaide, Adelaide, SA, Australia.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Ridding
authors.affiliation: The Robinson Research Institute, School of Medicine, University of Adelaide, Adelaide, SA, Australia.
authors.forename: Julia B
authors.initials: JB
authors.lastname: Pitcher
mesh_terms: D000293:Adolescent; D000328:Adult; D019540:Area Under Curve; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D008297:Male; D011930:Reaction Time / Q000502:physiology*; D012463:Saliva / Q000378:metabolism; D012691:Serial Learning / Q000502:physiology*; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology*; D055815:Young Adult
chemical_list: D006854:Hydrocortisone
keywords: Cognitive function; Cortisol; Cortisol awakening response; Diurnal cortisol rhythm; Learning; Serial sequence reaction time task