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Abstract:
Abstract: Anticipatory anxiety was experimentally induced to
study selective processing of anxiety-inducing threat stimuli.
Eighteen subjects were presented with two visual cues with a
differential instruction: one would occasionally be followed by an
aversive shock (threat), while the other would not (safe). The two
visual cues (square wave gratings) were presented with a duration
of 1.5 s in a randomized sequence. The instruction was reinforced
with a total of 12 wrist-shocks (reinforcing every 1 in 16 threat
cues). Startle reflex amplitude and State Anxiety Inventories were
employed to monitor anxiety induction. Anticipation of shock
induced by the threat cue in comparison with the safe condition
significantly affected both anxiety measures. This indicates that
the anxiety induced by the threat cue waxes and wanes dynamically
in the course of seconds. ERP measurement (32 channels) yielded a
difference potential with one component: a broadly distributed
posteriorly focused positive shift from 300 to 600 ms, lateralized
to the left (maximum at electrode-site PO3). Findings from
neuroimaging studies would predict the frontal areas with limbic
innervation to be involved in the response to threat stimuli. In
contrast, the present component probably reflects activity in
posterior areas, reflecting selective (threat vs. safe) stimulus
processing. However, it markedly differs from selection potentials
found in selective attention tasks using identical stimulus
material (Kenemans et al., 1993).
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