The effect of hypocapnia on extinction of conditioned fear responses

Conditioning models have been very helpful in the understanding of the etiology and maintenance of anxiety. Such laboratory models, however, leave unexplained why in many cases of naturally occurring anxiety, as in the case of agoraphobia, the fear responses do not extinguish. Literature on experimental anxiety provocation suggests that a systemic alkalosis might play a role in the maintenance of phobic fear. It was hypothesized that a subject in a state of respiratory alkalosis would show delayed extinction to classical conditioned anxiety. In a differential classical conditioning paradigm, consisting of a habituation-, an acquisition-, and an extinction-phase, slides and electric shocks were used as conditioned stimuli (CS) and unconditioned stimuli (US) respectively. The skin conductance response was taken as (U)CR. Subjects were randomly assigned to two groups: hyperventilation or control. It was shown that the extinction was not delayed when subjects were hypocapnic during the extinction. These data support the view that a respiratory alkalosis per se is not a sufficient condition for the maintenance of neurotic fears. The data of the present study are discussed in the context of existing literature on a psychological interpretation of the maintenance of anxiety.