title: Storm in a coffee cup: caffeine modifies brain activation to social signals of threat.
abstract: Caffeine, an adenosine A₁ and A(2A) receptor antagonist, is the most popular psychostimulant drug in the world, but it is also anxiogenic. The neural correlates of caffeine-induced anxiety are currently unknown. This study investigated the effects of caffeine on brain regions implicated in social threat processing and anxiety. Participants were 14 healthy male non/infrequent caffeine consumers. In a double-blind placebo-controlled crossover design, they underwent blood oxygenation level-dependent functional magnetic resonance imaging (fMRI) while performing an emotional face processing task 1 h after receiving caffeine (250 mg) or placebo in two fMRI sessions (counterbalanced, 1-week washout). They rated anxiety and mental alertness, and their blood pressure was measured, before and 2 h after treatment. Results showed that caffeine induced threat-related (angry/fearful faces > happy faces) midbrain-periaqueductal gray activation and abolished threat-related medial prefrontal cortex wall activation. Effects of caffeine on extent of threat-related amygdala activation correlated negatively with level of dietary caffeine intake. In concurrence with these changes in threat-related brain activation, caffeine increased self-rated anxiety and diastolic blood pressure. Caffeine did not affect primary visual cortex activation. These results are the first to demonstrate potential neural correlates of the anxiogenic effect of caffeine, and they implicate the amygdala as a key site for caffeine tolerance.
authors.affiliation: School of Experimental Psychology, University of Bristol, 12a Priory Road, Bristol BS8 1TU, UK. jessica.smith@bristol.ac.uk
authors.forename: Jessica E
authors.initials: JE
authors.lastname: Smith
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Lawrence
authors.forename: Ana
authors.initials: A
authors.lastname: Diukova
authors.forename: Richard G
authors.initials: RG
authors.lastname: Wise
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Rogers
mesh_terms: D000328:Adult; D000368:Aged; D001007:Anxiety / Q000139:chemically induced*; D062186:Arterial Pressure / Q000502:physiology; D001921:Brain / Q000187:drug effects*; D001931:Brain Mapping; D002110:Caffeine / Q000494:pharmacology*; D004311:Double-Blind Method; D019260:Expressed Emotion / Q000187:drug effects*; D005145:Face / Q000502:physiology; D005149:Facial Expression; D005239:Fear / Q000187:drug effects*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D012919:Social Behavior; D055815:Young Adult
chemical_list: D002110:Caffeine