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). While the younger adults (ages 20–29) startled most to loud noises while viewing unpleasant pictures, the older adults (ages 56–69) startled least while viewing the unpleasant pictures. The pattern Le Duc et al. found with younger adults is consistent with many previous studies in which undergraduates startled more to loud noises while viewing unpleasant pictures than while viewing pleasant pictures, with neutral pictures yielding startle levels in between the two valences Five-month-old infants showed the same pattern when viewing emotional faces (Balaban, 1995). Thus, this pattern of greater startle during exposure to negative than positive stimuli is a highly replicated finding. Lang (1995) proposed that startle is a defensive reaction augmented during aversive motivational states and dampened during approach states. This is now the dominant assumption in the field (e.g., Crowell et al., 2015). However, Le Duc et al.'s findings with older adults contradict this dominant assumption and reveal that we lack basic understanding about how emotion influences startle. Importantly, their surprising finding is not just a one-off finding. It replicates findings from another study comparing startle reactivity in younger adults (age 18–23) vs. older adults (ages 65–88) (Feng et al., 2011; Figure 1B). Thus, across two studies, older adults' results contradict the Lang (1995) model. Other than these two studies, I am not aware of any other emotion-startle data with older adults. From the perspective of the aging literature, it is not surprising that older adults would show a different impact of emotional pictures than younger adults. Previous findings indicated that younger and older adults show opposing affective biases in attention and memory, with younger