![]() These effects were observable before the subjects received any shock (a single stimulation of the median nerve). Two-factor analysis of variance (condition x block) showed that in the 'threat' condition there was a consistent increase in initial pupil diameter, a decrease in light reflex amplitude and an increase in alertness and anxiety ratings. At the end of each 'threat' or 'safe' block, subjects rated their anxiety using visual analogue scales. The shock consisted of a single square wave current pulse (1.5 mA, 50 msec) applied to the median nerve. The light reflex was recorded during either the anticipation of a shock ('threat' blocks) or periods in which no shocks were anticipated ('safe' blocks). Light stimuli (0.32 mW/cm(2), 200 msec) were generated by a light-emitting diode, and pupil diameter was monitored by computerized binocular infrared television pupillometry in the dark. We examined whether the threat of an electric shock, as used in the fear-potentiated startle paradigm, would affect the pupillary light reflex, in 12 healthy volunteers. ![]() It has been proposed that this paradigm may be a useful laboratory model of human anxiety. an electric shock ('fear-potentiated startle'). It has been shown that the eye-blink response evoked by an abrupt loud white noise ('acoustic startle') is potentiated when the subjects anticipate an aversive stimulus, e.g.
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