Age-related changes in prepulse inhibition of the startle response

Background:Acoustic prepulse inhibition of the startle response (PPI) is a phenomenon characterized by the reduction in the startle reflex caused by the presence of weak and brief stimulus before an intense and sudden stimulus (pulse). These phenomena can be observed in several species, but in humans it is commonly measured by the eyeblink using electromyography. PPI works as an operational measure of sensorimotor gating, which is the ability to suppress motor responses for sensory stimulus. Healthy aging is marked by several changes in neural processing, like inhibitory functioning decline. In this line, PPI measure can be a potential biomarker for changes related to the aging process.Methods:In this research we aim to investigate if PPI is reduced with aging and if this reduction would be associated with cognitive functioning of older adults. To this aim, we compared PPI levels of 14 cognitively  healthy older adults (over 60 years old) with PPI levels of 14 young adults (from 18 to 28 years old).Results:We  found significant differences in the PPI level  between the groups: F[1,25] = 7.44 p = 0.01 and lower startle amplitude (U = 26.000 p = 0.001) in older adults than in young adults. However, we did not find differences in levels of habituation , since the mean habituation percentage in young adults was 74.92% and in older adults was 82.9%. Independent samples T-test revealed no significant difference between groups in habituation: T = −1.1 p = 0.28. Furthermore, no correlation between PPI and cognition was found in the older adults group.Conclusion:  We found differences in PPI between the two investigated age groups. Therefore, taking age into account when using PPI as a biomarker in studies in different contexts is important, since age is a factor that has been shown to significantly affect the level of inhibition, regardless of differences in startle and auditory threshold.