Modulation of Prepulse Inhibition and Startle Reflex by Emotions: A Comparison between Young and Older Adults

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.

Commentary: Modulation of Prepulse Inhibition and Startle Reflex by Emotions: A Comparison between Young and Older Adults

“…Some findings overturn basic assumptions in the field and make it obvious how little we really understand. In my opinion, findings by Le Duc et al ( 2016 ) regarding age differences in how emotional stimuli influence startle reactivity fit this profile. They found age differences in how viewing pleasant, unpleasant and neutral pictures modulated a startle response to a loud noise (Figure 1A ).…”

“… Age-by-valence interactions in startle reactivity from (A) Le Duc et al ( 2016 ); and (B) Feng et al ( 2011 ) . …”

Induced Positive Affect Reduces the Magnitude of the Startle Response and Prepulse Inhibition

“…It is likely that the differences in the procedure employed to induce the affective state are responsible for some of the apparently contradictory results, since the remaining parameters used to record PPI are highly standardized (Geyer & Swerdlow, 1998), which makes it less likely that the differences were due to these parametric factors. Most of the studies in this field have presented IAPS images (Bradley & Lang, 2007) to induce the affective states (e.g., De la Casa et al, 2016, Experiment 1; Hawk & Kowmas, 2003), and none of these studies found a reduction in PPI (but see, Le Duc et al, 2016 that found a significant reduction in PPI for Young adults participants exposed to negative pictures, and a significant increase in PPI for older adults exposed to positive pictures). It is possible that presenting pictures of loved familiar faces was a more effective procedure for generating an intense positive affective response capable of disrupting PPI.…”

“…This enhanced sensorimotor gating can be explained from the model proposed by Schmajuk et al (2009) proposing that increased dopamine transmission in Ventral Tegmental Area will inhibit the process responsible of PPI. However, previous experiments analyzing the effect of different affective states on PPI evidenced a complex pattern of results – for instance, enhanced PPI in elderly adults when a positive affect was induced, and reduced PPI in young adults when the induced affect was negative (Le Duc et al, 2016). Until the nature of these discrepancies is elucidated, future research should take into account differences in age and, particularly, in the procedure employed to induce the affective state in the participants.…”

“…For instance, some studies have reported enhanced PPI following the induction of positive affect by IAPS pleasant images presentation (De la Casa et al, 2014, Experiment 1), while others have found that PPI remained intact (Hawk & Cook, 2000; Hawk & Kowmas, 2003). There is even a study that reported increased PPI in older adults ( M age = 63.6 years) while viewing pleasant images, but this effect was reversed for younger adults ( M age = 24 years) that showed reduced PPI while viewing aversive pictures (Le Duc, Fournier, & Hébert, 2016).…”