Modality-specific attention under imminent but not remote threat of shock: evidence from differential prepulse inhibition of startle.

Theories of animal defensive behavior postulate that imminent, predictable threat elicits highly focused attention toward the threat source, whereas remote, unpredictable threat elicits distributed attention to the overall environment. We used threat of shock combined with measurement of prepulse inhibition of the startle reflex to test these claims in humans. Twenty-seven participants experienced periods of threat and safety. Threat and safe periods were short or long, with the short threat periods conveying relatively predictable, imminent shocks and the long threat periods conveying unpredictable shocks. Startle reflexes were elicited with equal numbers of acoustic probes presented alone, preceded by a tactile prepulse, or preceded by an auditory prepulse. We observed enhanced tactile relative to auditory prepulse inhibition during short threat periods only. This finding supports the notion that imminent threat, but not remote threat, elicits attention focused toward the relevant modality, potentially reflecting preparatory activity to minimize the impact of the noxious stimulus.