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Prepulse reactivity in prepulse inhibition. / Ewa G Truchanowicz
Swansea University Author: Ewa G Truchanowicz
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Prepulse inhibition (PPI) is a popular paradigm in sensorimotor gating research. In healthy individuals the weak lead stimulus (i.e., the prepulse) presentation results in a reduction in the startle probe (pulse) elicited response. The motor responses to the prepulses (prepulse reactivity, PPER) wer...
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Prepulse inhibition (PPI) is a popular paradigm in sensorimotor gating research. In healthy individuals the weak lead stimulus (i.e., the prepulse) presentation results in a reduction in the startle probe (pulse) elicited response. The motor responses to the prepulses (prepulse reactivity, PPER) were until recently largely ignored in PPI research. There are conflicting reports about prepulse reactivity and startle response modification (SRM) associations; and personality factors relevant to SRM have not been previously examined in prepulse reactivity context. Healthy participants were drawn from university student and staff population. Three paradigms were used: unpredictable stimulus onset, predictable stimulus onset and conscious stimulus processing. The stimuli consisted of 80, 85 & 90dB prepulses and 115dB startle probe separated by 140ms inter-stimulus interval (onset to onset asynchrony). The inter-trial intervals varied between the studies. Startle responses were measured as eye blinks and recorded using surface EMG. All motor responses were quantified according to the same set of rules. Prepulse-elicited motor responses reliably appeared in all the studies and were distinct from spontaneous EMG. Some PPER characteristics exhibited stimulus intensity dependence further proving PPER validity as stimulus-driven response. Prepulse reactivity exhibited significant associations with startle response modification. PPER was a stable tendency; individuals either consistently responded to the weak lead stimuli or did not. Two types of startle response modification appeared under the conditions assumed to elicit maximal inhibition only: classical inhibition (as expected) and paradoxical prepulse facilitation. These appeared in motor responses and in conscious stimulus processing. The propensity towards the paradoxical prepulse facilitation was reduced by efficient prepulse inhibition. PPER and SRM had limited associations with personality factors, sex, or age. The predictable stimulus onset paradigm however highlighted the associations of the defensive startle response and its modification with fear and anxiety. Increased emotionality, regardless of its valence, proved detrimental to sensorimotor gating.
Faculty of Medicine, Health and Life Sciences