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Is the hippocampus necessary for contextual fear conditioning?
J C Gewirtz1, K A McNish, M Davis
1Department of Psychiatry, Yale University School of Medicine, Ribicoff Research Facilities of the Connecticut Mental Health Center, 34 Park Street, New Haven, CT 06508, USA. jgewirtz@tc.umn.edu
Behavioural Brain Research
|May 10, 2000
Summary
The hippocampus may not be critical for contextual learning. Lesions in the dorsal hippocampus disrupt freezing behavior, but not contextual fear itself, suggesting a role in expression rather than learning.
Area of Science:
- Neuroscience
- Behavioral Neuroscience
- Learning and Memory
Background:
- The hippocampus is traditionally considered crucial for contextual fear conditioning.
- Evidence suggests dorsal hippocampus lesions impair freezing responses to contextual cues.
Purpose of the Study:
- To investigate the role of the hippocampus in contextual fear learning versus the expression of fear responses.
- To re-evaluate the necessity of the hippocampus for contextual learning.
Main Methods:
- Lesion studies of the dorsal hippocampus in rats.
- Assessment of fear conditioning using freezing behavior and fear-potentiated startle.
- Evaluation of the contextual blocking phenomenon.
Main Results:
- Dorsal hippocampus lesions disrupted freezing behavior but not fear-potentiated startle or contextual blocking.
- Rats with hippocampal lesions showed deficits in both contextual and unconditioned freezing.
- Contextual learning appears spared after hippocampal lesions in several paradigms.
Conclusions:
- Hippocampal lesions primarily disrupt the expression of freezing, not contextual fear itself.
- Contextual learning is generally spared after dorsal hippocampus lesions.
- The hippocampus may play a role in contextual learning only under specific, yet undefined, conditions.
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