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Amygdala, hippocampus, and unconditioned fear
1Department of Psychology, University of Toronto, 100 St. George St., Toronto, Ontario M5S 3G3, Canada. elena@psych.utoronto.ca
Experimental Brain Research
|June 22, 2001
Summary
The amygdala and hippocampus are crucial for forming fear memories, not for performing fear responses. Damage to these brain areas impairs memory but not the expression of fear itself.
Area of Science:
- Neurobiology
- Cognitive Neuroscience
- Behavioral Neuroscience
Background:
- The amygdala's role in fear conditioning memory formation versus fear response performance is debated.
- Existing research presents conflicting views on whether the amygdala is essential for memory consolidation or response execution.
Purpose of the Study:
- To investigate the specific role of the amygdala and hippocampus in fear memory and response performance.
- To differentiate between memory impairment and performance deficits in fear conditioning.
Main Methods:
- Rats with amygdala or hippocampal damage were tested for unconditioned fear responses to footshock.
- The same animals were assessed for conditioned fear responses to cues previously paired with footshock.
Main Results:
- Rats with amygdala or hippocampal damage showed no impairment in unconditioned fear responses (freezing, urination, defecation, locomotion).
- These animals also did not differ from sham-operated controls in conditioned fear responses during testing.
Conclusions:
- Damage to the amygdala or hippocampus impairs the mnemonic processes of fear conditioning.
- These brain structures are not required for the performance of unconditioned fear responses per se.