Abstract
Eyeblinks, whether reflexive or voluntary, play an important role in protecting our vision. When viewing pictures, reflexive eyeblinks are known to be modulated by the emotional state induced thereby. More specifically, the hedonic valence (unpleasantness-pleasantness) induced by the picture has been shown to have a linear relationship with the amplitude of a startle blink elicited during picture viewing. This effect has been attributed to congruence between an ongoing state and task demands: an unpleasant emotional state is assumed to bias our attention towards potentially harmful stimuli, such as startle tones. However, recent research suggests that the valence-specific modulation may not be limited to the sensory parts of the reflexive pathway related to startle responses. Here, we examined the effect of emotional picture viewing on voluntary (in response to a written command) eyeblinks in adult humans. Emotional modulation of startle blinks was also evaluated. We found that when viewing unpleasant pictures, the amplitude of reflexive eyeblinks was augmented, but the amplitude of voluntary eyeblinks was unaffected. Nevertheless, the response latencies of voluntary eyeblinks were found to be delayed during the viewing of pleasant and unpleasant relative to neutral pictures. We conclude that these results support the theory that emotional experience augments sensory processing specific to potentially harmful stimuli. Further, the emotional state seems not to exert an effect on voluntarily elicited motor activity.
Highlights
Emotional state, its hedonic valence, modulates defensive reflexes [1,2]
We presented the participants with unpleasant, neutral and pleasant emotional images drawn from the International Affective Picture System; IAPS [9] and measured their voluntary eyeblinks and acoustic startle stimulus-evoked reflexive eyeblinks
We examined whether voluntary eyeblinks are affected by emotional state and, if so, whether the underlying mechanisms could be regarded as the same, or at least as analogous with the mechanisms underlying reflexive eyeblinks, in the sense that they would relate to the valence of an emotion as predicted by the motivational priming hypothesis [3]
Summary
Its hedonic valence, modulates defensive reflexes [1,2]. The most common way to examine emotional reflex modulation is to assess the effect of emotional picture viewing on the amplitude of the eyeblink component of the acoustic startle reflex. According to the motivational priming hypothesis [3], emotional picture viewing mobilizes a motivational system that, in turn, facilitates the accessibility of motor action programs that correspond to the state of this system with respect to the hedonic valence of an emotion. The modulation effect has been attributed to valence Pictures with both high and low hedonic valence values induce heightened arousal, arousal does not affect startle amplitudes [3]
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