Abstract
This study examined whether or not the acoustic startle response and sensorimotor gating may be modulated by emotions differentially between young and older adults. Two groups of participants (mean age Young: 24 years old; Elderly: 63.6 years old) were presented with three types of auditory stimuli (Startle alone, High or Low frequency Prepulse) while viewing pleasant, neutral, or unpleasant images. Electromyographic activity of the eyeblink response was measured. Results show that older adults displayed diminished eyeblink responses whereas younger adults displayed enhanced eyeblink responses when viewing negative images. Sensorimotor gating also differed between young and older adults, with enhanced sensorimotor gating abilities while viewing positive pictures in older adults and diminished abilities while viewing negative pictures among younger adults. These results argue in favor of a differential emotional influence on the sensorimotor abilities of young and older adults, with a positivity bias among the latter.
Highlights
The acoustic startle reflex is a cross-species, whole-body reflex in response to a loud and unexpected sound
It is observable that Elderly had overall much smaller blink responses (M = 61 μV, SD = 81 μV) than Young adults (M = 157 μV, SD = 76 μV)
The main group effect was no longer significant, F(1,58) = 2.21, p = 0.09, but the two-way interaction Emotion × Group was, F(2,106) = 8.44, p < 0.001, ηp2 = 0.137: as expected, Young adults displayed significantly greater startle reflex reactivity for unpleasant compared to neutral pictures, t(25) = −2.98, p = 0.006, with means of 0.78 (SD = 0.5) and
Summary
The acoustic startle reflex is a cross-species, whole-body reflex in response to a loud and unexpected sound. Its basic circuitry is relatively simple (Cook et al, 1991; Kofler et al, 2001) and it is measured in humans by the magnitude and latency of the eyeblink, one component of the startle response. PPI itself can be modulated via descending projections from central brain structures such as auditory cortex and limbic circuitry (Li et al, 2009). This modulation determines how strongly the prepulse will inhibit the subsequent neural response from the facial motor nucleus responsible of the startle response (Swerdlow et al, 2001). The purpose of the present study was to characterize the interaction between emotion and aging on the startle reflex and its inhibition by a prepulse
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