Dissociation of tactile and acoustic components in air puff startle

Tactile (air puff) or acoustic startle stimuli elicit behavioral (motor) and complex cardiovascular responses which include pressor as well as cardiac decelerative and accelerative responses. An acoustic component of the air puff stimulus (12.5 psi) was identified. Studies were conducted to separate the contributions of both stimulus modalities to the observed responses. The acoustic component was approximated with a wide-spectrum 97-dB white-noise stimulus. This acoustic stimulus failed to evoke heart rate responses but did yield motor and pressor responses. In a second approach, tympanic membrane rupture (TMR) was used to interrupt acoustic sensory stimuli. TMR fully abolished the motor and pressor responses to acoustic startle. With air puff startle, while TMR severely attenuated the motor response it only decreased slightly the pressor and cardiac accelerative responses and failed to influence the cardiac decelerative component. Our results indicate that air puff startle contains both tactile and acoustic modalities. Further, the motor response is largely driven by the acoustic modality since TMR abolished this response elicited by either acoustic or tactile stimulation. More importantly, motor and cardiovascular responses to startle may be separated through discrimination of afferent stimuli suggesting either differences in neural pathways for acoustic and tactile stimuli or a differential dependency of the various responses on stimulus characteristics.