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Physiological changes during tonic immobility in Gallus gallus var domesticus
M J Gentle1, R B Jones, S C Woolley
1AFRC Institute of Animal Physiology and Genetics Research, Midlothian, U.K.
Physiology & Behavior
|November 1, 1989
Summary
Tonic immobility (TI) in hens initially causes EEG arousal but shifts to a deactivated state, indicating reduced sympathetic activity and fear. Core body temperature remained stable during the immobility response.
Area of Science:
- Animal behavior
- Neuroscience
- Physiology
Background:
- Tonic immobility (TI) is a natural defensive behavior observed in prey animals.
- Understanding the physiological underpinnings of TI is crucial for comprehending fear responses.
Purpose of the Study:
- To investigate the physiological changes in hens during tonic immobility.
- To explore the relationship between EEG patterns, autonomic activity, and behavior during TI.
Main Methods:
- Induction of tonic immobility in hens.
- Monitoring of electroencephalogram (EEG) activity.
- Measurement of shank temperature and heart rate.
- Assessment of sympathetic nervous activity via physiological indicators.
Main Results:
- TI induction initially correlated with EEG arousal, decreased shank temperature, and increased heart rate.
- Subsequently, EEG showed slow-wave patterns, muscle tone decreased, and sympathetic activity reduced (lower heart rate, vasodilation).
- Core body temperature remained constant at 42°C; EEG-behavioral dissociation was observed.
Conclusions:
- Tonic immobility involves a complex interplay of initial arousal followed by a deactivated state.
- Physiological changes suggest a "cut-off" mechanism for the fear state during sustained immobility.
- Observed EEG-behavioral dissociation warrants further investigation into fear processing.