title: Defensive eye-blink startle responses in a human experimental model of anxiety.
abstract: Inhalation of low concentrations of carbon dioxide (CO2) triggers anxious behaviours in rodents via chemosensors in the amygdala, and increases anxiety, autonomic arousal and hypervigilance in healthy humans. However, it is not known whether CO2 inhalation modulates defensive behaviours coordinated by this network in humans. We examined the effect of 7.5% CO2 challenge on the defensive eye-blink startle response. A total of 27 healthy volunteers completed an affective startle task during inhalation of 7.5% CO2 and air. The magnitude and latency of startle eye-blinks were recorded whilst participants viewed aversive and neutral pictures. We found that 7.5% CO2 increased state anxiety and raised concurrent measures of skin conductance and heart rate (HR). CO2 challenge did not increase startle magnitude, but slowed the onset of startle eye-blinks. The effect of CO2 challenge on HR covaried with its effects on both subjective anxiety and startle latency. Our findings are discussed with reference to startle profiles during conditions of interoceptive threat, increased cognitive load and in populations characterised by anxiety, compared with acute fear and panic.
authors.affiliation: Psychology, University of Southampton, Southampton, UK.
authors.forename: Verity
authors.initials: V
authors.lastname: Pinkney
authors.affiliation: Department of Pharmacy and Pharmacology, University of Bath, Bath, UK.
authors.forename: Robin
authors.initials: R
authors.lastname: Wickens
authors.affiliation: Psychology, University of Southampton, Southampton, UK.
authors.forename: Susan
authors.initials: S
authors.lastname: Bamford
authors.affiliation: Clinical and Experimental Sciences, University of Southampton, Southampton, UK.
authors.forename: David S
authors.initials: DS
authors.lastname: Baldwin
authors.affiliation: Psychology, University of Southampton, Southampton, UK Clinical and Experimental Sciences, University of Southampton, Southampton, UK m.j.garner@soton.ac.uk.
authors.forename: Matthew
authors.initials: M
authors.lastname: Garner
mesh_terms: D000293:Adolescent; D000328:Adult; D001007:Anxiety / Q000139:chemically induced* / Q000503:physiopathology*; D001767:Blinking / Q000187:drug effects / Q000502:physiology*; D002245:Carbon Dioxide / Q000494:pharmacology*; D018592:Cross-Over Studies; D005260:Female; D005712:Galvanic Skin Response / Q000187:drug effects / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008297:Male; D008960:Models, Psychological; D010775:Photic Stimulation; D013216:Reflex, Startle / Q000187:drug effects / Q000502:physiology*; D016037:Single-Blind Method; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide
keywords: Anxiety; carbon dioxide inhalation; defensive behaviour; emotional response; eye-blink startle response; heart rate; skin conductance; startle