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Darkness facilitates the acoustic startle reflex in humans
C Grillon1, M Pellowski, K R Merikangas
1Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Biological Psychiatry
|September 15, 1997
Summary
Darkness significantly amplifies startle responses but does not alter prepulse inhibition (PPI). This suggests that the heightened startle in the dark is linked to emotional factors, not attentional changes.
Area of Science:
- Psychology
- Neuroscience
- Sensory Perception
Background:
- The startle reflex is a fundamental protective mechanism.
- Pre-pulse inhibition (PPI) is a measure of sensorimotor gating.
- Environmental factors like light can modulate physiological responses.
Purpose of the Study:
- To investigate the impact of darkness on startle reactivity.
- To examine the effect of darkness on prepulse inhibition (PPI).
- To explore the relationship between fear of the dark and startle responses in darkness.
Main Methods:
- Two studies were conducted with 25 participants each.
- Acoustic startle stimuli were presented in alternating periods of light and complete darkness.
- Pre-pulse inhibition (PPI) was measured by preceding startle stimuli with a non-startling prepulse.
- Retrospective rating scales assessed childhood fear of the dark.
Main Results:
- Darkness significantly increased the magnitude of the acoustic startle response in both studies.
- Darkness did not significantly affect prepulse inhibition (PPI).
- Increased startle magnitude in darkness correlated with retrospective ratings of childhood fear of the dark.
Conclusions:
- The facilitation of the startle reflex in darkness is likely mediated by affective (emotional) processes rather than attentional shifts.
- Findings suggest that fear of the dark may play a role in heightened startle responses in low-light conditions.
- Darkness does not appear to enhance attention to auditory stimuli as measured by PPI.