title: Inhalation of 7.5% carbon dioxide increases alerting and orienting attention network function.
abstract: BACKGROUND
  The development of experimental models that readily translate between animals and humans is required to better integrate and clarify the biological, behavioural and cognitive mechanisms that underlie normal fear and pathological anxiety. Inhalation of low concentrations of carbon dioxide (CO(2)) increases anxiety and autonomic arousal in humans, triggers related behaviours in small animals, and increases selective attention to threat in healthy humans. However the effects on broader cognitive (non-emotional) processes that characterize anxiety are not known.
  
  
  OBJECTIVE
  To examine the effect of 7.5 % CO(2) inhalation (vs. air) on the efficiency of discrete attention networks implicated in anxiety: alerting (maintaining an alert state), orienting (the selection of information from sensory input) and executive control (resolving cognitive conflict).
  
  
  METHODS
  Twenty-three healthy human participants completed a computerized Attention Network Test (ANT) during inhalation of 7.5 % CO(2) enriched and normal/medical air. Gas was administered blind to participants with inhalation order counterbalanced across participants. Measures of heart rate, blood pressure and subjective mood/anxiety were obtained at baseline and following each inhalation period.
  
  
  RESULTS
  CO(2) inhalation increased anxiety, autonomic arousal and the efficiency of alerting and orienting attention network function. Autonomic response to CO(2) correlated with increased orienting; and CO(2)-induced anxiety, autonomic arousal and orienting network function increased with chronic (trait) anxiety.
  
  
  CONCLUSIONS
  Evidence that CO(2) modulates attention mechanisms involved in the temporal detection and spatial location of salient stimuli converges with evidence that CO(2) triggers fear behaviour in animals via direct innervation of a distributed neural network that facilitates environmental hypervigilance.
authors.affiliation: Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, SO17 1BJ, UK. m.j.garner@soton.ac.uk
authors.forename: Matthew
authors.initials: M
authors.lastname: Garner
authors.forename: Angela
authors.initials: A
authors.lastname: Attwood
authors.forename: David S
authors.initials: DS
authors.lastname: Baldwin
authors.forename: Marcus R
authors.initials: MR
authors.lastname: Munafò
mesh_terms: D000280:Administration, Inhalation; D001007:Anxiety / Q000139:chemically induced*; D001143:Arousal / Q000187:drug effects; D001288:Attention / Q000187:drug effects; D001341:Autonomic Nervous System / Q000187:drug effects / Q000378:metabolism; D002245:Carbon Dioxide / Q000008:administration & dosage / Q000633:toxicity*; D003220:Conflict, Psychological; D018592:Cross-Over Studies; D005239:Fear / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D009415:Nerve Net / Q000378:metabolism*; D009483:Neuropsychological Tests; D016037:Single-Blind Method; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide