Abstinent coffee drinkers (n = 60) consumed decaffeinated coffee with either 280 mg or 0 mg added caffeine. Caffeine dose was crossed with varying instructions that the coffee would either enhance or impair performance in a selleck 2 x 2 factorial design. Performance, mood, caffeine withdrawal, and negative somatic effects were assessed.
Relative to placebo, caffeine improved reaction time and accuracy on the rapid visual information processing task, a measure of vigilance. However, there was a significant dose by expectancy interaction that revealed
that among participants given placebo coffee, “”impair”" instructions produced better performance than “”enhance”" instructions. Caffeine also improved psychomotor performance as indicated by a finger tapping task with no main effects of expectancy or interactions. Impair instructions produced greater reports of negative somatic effects than enhance instructions, but only when caffeine was administered.
Manipulating the expected effects of caffeine altered the behavioral and subjective effects of caffeine. A significant dose by expectancy interaction revealed a somewhat paradoxical outcome in the placebo conditions whereby those told “”impair”" performed better than those told “”enhance.”" This may reflect Sotrastaurin mouse compensatory responding
as has been observed in similar studies using alcohol (Fillmore et al. Psychopharmacology 115:383-388, 1994). Impair instructions led to greater negative somatic effects only when caffeine was administered supporting the active placebo hypothesis.”
“Aim: The brain neurotransmitter serotonin affects many
aspects of human behavior, including personality traits. Because the RAD001 serotonin receptor 2B (HTR2B) gene has recently been associated with impulsivity, we investigated the potential association between the rs10194776 and Q20* polymorphism in the HTR2B gene and personality traits in healthy subjects. Methods: A total of 1,171 healthy Japanese subjects were enrolled in this study. Their personality traits were evaluated using the Temperament and Character Inventory (TCI), and the rs10194776 and Q20* genotype was determined using real-time polymerase chain reaction. Results: There was a significant main effect of the rs10194776 polymorphism on harm avoidance and self-directedness in females (p = 0.037 and p = 0.043, respectively). However, these differences were insignificant after a Bonferroni correction. Subjects carrying the minor allele of the Q20* polymorphism were nonexistent. Conclusion: The results of the present study suggest that the HTR2B polymorphism is not likely to be associated with personality traits, including novelty seeking and impulsivity. Copyright (c) 2013 S.