Effects of prepulse format and lead interval on the assessment of automatic and attention-modulated prepulse inhibition

Prepulse inhibition (PPI) of the acoustic startle response can index automatic and attention-modulated aspects of sensorimotor gating. Automatic sensorimotor gating is typically assessed by a no-task PPI protocol in which participants are presented with discrete white noise prepulse and startle stimuli over continuous background broadband noise at brief short-lead intervals (e.g., 60–120 ms). In contrast, attention-modulated sensorimotor gating is typically assessed through a task-based PPI protocol using continuous format pure tone prepulses and white noise startle stimuli presented over an ambient background at a lead interval of 120 ms. The present study sought to test the extent that the assessment of attention-modulated PPI is dependent on prepulse type and lead interval across two experiments. Experiment 1 assessed attention effects on PPI produced by discrete prepulses at lead intervals of 60 and 120 ms. Experiment 2 examined attention effects on PPI with matched stimulus conditions apart from continuous prepulses. Results indicated that the use of discrete prepulses failed to elicit attentional-modulation of PPI and that assessment therein was dependent on the use of continuous prepulses at a lead interval of 120 ms. These results highlight additional methods to concurrently assess automatic and attention-modulated PPI in a single testing session using a task-based tone counting task.