title: Brainstem correlates of defensive states in humans.
abstract: BACKGROUND
  Brainstem auditory evoked potentials (BAEP) reflect the activation of brainstem nuclei in the first milliseconds after presentation of an auditory stimulus. These electrophysiological correlates of neural processing are highly automatic and not influenced by cognitive factors or task demands; however, data from patients with anxiety disorders suggest deviations in the BAEP. It has been hypothesized that these differences reflect heightened activation of structures involved in defensive states, such as the amygdala and locus coeruleus, projecting to the inferior colliculus, one of the brainstem generators of wave V of the BAEP. The present study investigated this possibility by testing BAEP during experimentally induced anxiety in healthy volunteers.
  
  
  METHODS
  In this study, BAEP were recorded from healthy normal volunteers under threat of shock, compared with safe conditions.
  
  
  RESULTS
  The first experiment (n = 12) showed that shock anticipation increased the amplitude of wave V. A replication experiment (n = 13) confirmed this finding.
  
  
  CONCLUSIONS
  Although BAEP are highly robust with respect to attentional manipulations, they are affected by transient activation of the fear system due to threat of shock. This finding indicates that some of the electrophysiological brainstem abnormalities observed in anxiety disorders can be replicated in healthy control subjects by inducing a transient state of anxiety.
authors.affiliation: National Institute of Mental Health, Mood and Anxiety Disorders Program, Bethesda, Maryland, USA. j.m.p.baas@fss.uu.nl
authors.forename: Johanna M P
authors.initials: JM
authors.lastname: Baas
authors.forename: Jean
authors.initials: J
authors.lastname: Milstein
authors.forename: Meghan
authors.initials: M
authors.lastname: Donlevy
authors.forename: Christian
authors.initials: C
authors.lastname: Grillon
mesh_terms: D000328:Adult; D001008:Anxiety Disorders / Q000523:psychology; D001288:Attention / Q000502:physiology; D001933:Brain Stem / Q000502:physiology*; D003674:Defense Mechanisms; D004566:Electrodes; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005239:Fear; D005260:Female; D006801:Humans; D007245:Inferior Colliculi / Q000502:physiology; D008297:Male; D013997:Time Factors