Background noise decreases both prepulse elicitation and inhibition of acoustic startle blink responding.

Prepulse inhibition of startle (PPI) has proved to be useful in distinguishing between schizophrenia patients and normal controls, although not all studies in this area find such group differences. One reason for this inconsistency may be the fact that some research labs present the startle eliciting and inhibiting stimuli over a steady background noise (70 dB), whereas others present stimuli in ambient noise conditions (30-56 dB). The present study tested the impact of background noise (30, 50, and 70 dB) on PPI in normal college adults, with prepulses at intensities of 75, 80, and 85 dB, and with prepulse rise times of 1 or 10 ms. Background noise decreased the amount of PPI caused by the prepulses, and also decreased the ability of the prepulses to themselves elicit blink responses. We conclude that background noise interferes with the processing of the prepulse, attenuating its effect as both an elicitor and inhibitor of the startle reflex. By elevating the difficulty of prepulse processing, this attenuation may be a necessary condition for observing differences in PPI between patient and control groups.