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Startle potentiation: shock sensitization, aversive learning, and affective picture modulation
M K Greenwald1, M M Bradley, B N Cuthbert
1Center for the Study of Emotion and Attention, University of Florida, USA. mgreen@med.wayne.edu
Behavioral Neuroscience
|November 26, 1998
Summary
Aversive stimulation, like shock exposure, significantly enhances the acoustic startle reflex in humans through sensitization. This sensitization is a more robust defensive response than conditioning or picture modulation effects.
Area of Science:
- Psychology
- Neuroscience
- Human Physiology
Background:
- The acoustic startle reflex, a defensive response, can be modulated by aversive stimuli.
- Previous research in animals and humans shows potentiation through shock exposure, conditioning, and unpleasant images.
Purpose of the Study:
- To investigate the magnitude and relationship between different types of aversive stimulation on the acoustic startle reflex in humans.
- To compare the effects of shock exposure, associative shock conditioning, and unpleasant picture viewing on startle reflex modulation.
Main Methods:
- Human volunteers were exposed to different aversive stimuli, including shock exposure and a control task.
- The probe-startle response was measured to quantify the modulatory effects.
- Statistical analyses were performed to compare the magnitude of effects and their correlations.
Main Results:
- Dramatic sensitization of the probe-startle response was observed after shock exposure, exceeding control task effects.
- Sensitization magnitude was significantly greater than that of associative shock conditioning and picture modulation.
- Sensitization and conditioning scores correlated modestly, suggesting partially overlapping neural mechanisms.
Conclusions:
- Startle reflex sensitization following shock exposure is a robust defensive response in humans.
- The findings align with animal data suggesting overlapping brain pathways, like amygdaloid-reticular projections, mediate these responses.
- Sensitization appears to be a more potent modulator of the startle reflex than associative conditioning or unpleasant imagery.