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In complex vertebrates, including humans, the amygdala perform primary roles in the formation and storage of memories associated with emotional events. Research indicates that during fear conditioning, sensory stimuli reach the basolateral complexes of the amygdalae, particularly the lateral nuclei, where they form associations with memories of the stimuli. The association between stimuli and the aversive events they predict may be mediated by long-term potentiation, a lingering potential for affected synapses to react more readily.
Memories of emotional experiences imprinted in reactions of synapses in the lateral nuclei elicit fear behavior through connections with the central nucleus of the amygdalae. The central nuclei are involved in the genesis of many fear responses, including freezing (immobility), tachycardia (rapid heartbeat), increased respiration, and stress-hormone release. Damage to the amygdalae impairs both the acquisition and expression of Pavlovian fear conditioning, a form of classical conditioning of emotional responses.
Stathmin gene and AmygdalaEdit
Recent research works by Dr. Gleb Shumyatsky and Prof. Eric Kandel have led to the identification of the Stathmin gene. This gene is highly enriched in the amygdala and is believed to be involved in controlling both innate and learned fear in mice. They "knocked out" the stathmin gene in the amygdala using gene knockout technology and found that mice that lacked stathmin gene lacked any kind of fear. For instance, such mice did not freeze on sighting a cat.
References & BibliographyEdit
- Cahill, L., Vazdarjanova, A. and Setlow, B. (2000). The basolateral amygdala complex is involved with, but is not necessary for, rapid acquisition of Pavlovian "fear" conditioning , European Journal of Neuroscience 12, 3044-50.
- Davis, M., (2000). The role of the amygdala in conditioned and unconditioned fear and anxiety , in Aggleton, J. P. (ed.), The Amygdala: A Functional Analysis, Oxford University Press, London.
- Killcross, S., Robbins, T. W., and Everitt, B. J. (1997). Different types of fear-conditioned behaviour mediated by separate nuclei within amygdala , Nature 388, 377-80.
- LeDoux, J., (2000). The amygdala and emotion: a view through fear , in Aggleton, J. P. (ed.), The Amygdala: A Functional Analysis, Oxford University Press, London.
- Vazdarjanova, A. and McGaugh, J. L., (1998). Basolateral amygdala is not a critical locus for memory of contextual fear conditioning , Proceedings, National Academy of Sciences, USA 95, 15003-7.
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