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Atropine stereotypy as a behavioral trap: a movement subsystem and electroencephalographic analysis
Journal of Comparative and Physiological Psychology
|February 1, 1980
Summary
Atropine sulfate causes rats to exhibit exaggerated snout thigmotaxis and stereotyped scanning behaviors. Environmental changes can alter this behavior, suggesting it is a reflexive reaction, not a motor automatism.
Area of Science:
- Neuroscience
- Behavioral Pharmacology
- Animal Behavior
Background:
- Anticholinergic drugs like atropine sulfate can induce stereotyped behaviors and alter electroencephalographic (EEG) activity.
- Stereotyped behaviors are repetitive, invariant motor acts with no obvious goal or function.
- Thigmotaxis, or contact-seeking behavior, is common in rodents and can be influenced by environmental stimuli.
Purpose of the Study:
- To analyze the movement subsystems and EEG activity associated with atropine-induced stereotyped behaviors in rats.
- To investigate the role of snout thigmotaxis in the observed stereotyped scanning.
- To explore the relationship between hippocampal theta activity, behavioral sequencing, and atropine's effects.
Main Methods:
- Rats were administered atropine sulfate (50-75 mg/kg) to induce stereotyped behaviors.
- Behavioral analysis focused on scanning patterns in an alleyway, with environmental modifications (e.g., low roof).
- EEG activity, including hippocampal theta and neocortical patterns, was recorded and analyzed in conjunction with behavior.
Main Results:
- Atropine sulfate induced exaggerated snout thigmotaxis, leading to prolonged scanning at the closed end of an alleyway.
- Behavioral patterns were modifiable by environmental changes, indicating a chain of reflexive reactions rather than motor automatism.
- Atropine blocked brief hippocampal theta periods observed during rapid directional shifts in undrugged rats.
- Reduced head scanning and increased immobility with sleeplike EEG patterns occurred under a low roof, contrasting with activated EEG during scanning.
Conclusions:
- Atropine-induced stereotyped scanning is a reflexive response to sensory input, particularly exaggerated snout thigmotaxis, rather than an intrinsic motor program.
- The blockade of hippocampal theta by atropine may impair normal behavioral sequencing, contributing to the failure to adapt.
- Scanning stereotypy and activated EEG appear to be maintained by movement-concurrent positive feedback mechanisms.