Key result
Threat of electric shock or acoustic sound blast inhibited the light reflex amplitude across all light probe intensities compared to white noise alone.
Threat of shock or sound blast inhibits the light reflex, with the effect increasing at higher light probe intensities.
Threat modulation of pupillary light reflex extends autonomic threat-response models; leaves open clinical translation or diagnostic use.
The effect of various parameters on the mediation of the fear-inhibited light reflex was examined. The light reflexes of 16 healthy men were measured across four light probe intensities, either in the presence of white noise alone or when the white noise was associated with the threat of either an electric shock or an acoustic sound blast. The white noise alone did not affect the light reflex amplitude. Both types of threat were subjectively anxiogenic and inhibited the light reflex across all light probe intensities, the threat of shock being more potent than the threat of sound blast. Importantly, the effect of either type of threat on the light reflex amplitude was found to increase with increasing light probe intensity, suggesting that brighter light probes may become more relevant motivationally in the threat condition, thus attracting greater allocation of attentional/cognitive resources.
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Hourdaki et al. (2005) studied Healthy (n=16). Threat of electric shock or acoustic sound blast vs. White noise alone was evaluated on Light reflex amplitude. Threat of electric shock or acoustic sound blast inhibited the light reflex amplitude across all light probe intensities compared to white noise alone.
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