• Christian Grillon, Johanna M P Baas, Brian Cornwell, and Linda Johnson.
• Mood and Anxiety Disorders Program, National Institute of Mental Health, NIH, DHHS, Bethesda, Maryland 20892-2670, USA. grillonc@intra.nimh.nih.gov
• Biol. Psychiatry. 2006 Oct 1; 60 (7): 752-9.

BackgroundSustained anxiety can be modeled using context conditioning, which can be studied in a virtual reality environment. Unpredictable stressors increase context conditioning in animals. This study examined context conditioning to predictable and unpredictable shocks in humans using behavioral avoidance, potentiated startle, and subjective reports of anxiety.MethodsSubjects were guided through three virtual rooms (no-shock, predictable, unpredictable contexts). Eight-sec duration colored lights served as conditioned stimuli (CS). During acquisition, no shock was administered in the no-shock context. Shocks were paired with the CS in the predictable context and were administered randomly in the unpredictable context. No shock was administered during extinction. Startle stimuli were delivered during CS and between CS to assess cued and context conditioning, respectively. To assess avoidance, subjects freely navigated into two of the three contexts to retrieve money.ResultsStartle between CS was potentiated in the unpredictable context compared to the two other contexts. Following acquisition, subjects showed a strong preference for the no-shock context and avoidance of the unpredictable context.ConclusionsConsistent with animal data, context conditioning is increased by unpredictability. These data support virtual reality as a tool to extend research on physiological and behavioral signs of fear and anxiety in humans.

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