Another topic recommended by a student involves the genetic basis of fear. Most rodents are terribly afraid of open spaces, and for logical reasons. If a rodent is on the floor (I’ve inadvertently dropped a few in my lab days), it will run directly for the wall. This is likely an example of innate fear in rodents. Rodents are also quite capable of learning to fear, as thousands of classical conditioning experiments will attest.
The amygdala appears to play an essential role in both innate and learned fear. Eric Kandel and his colleagues found two genes, gastrin-releasing peptide (GRP) and stathmin, that were much more active than in other parts of the brain that are not related to processing fear [1]. In particular, the stathmin gene was expressed throughout the brain’s fear circuitry.
To further explore the role of stathmin in fear, Kandel et al. genetically engineered mice who lacked the stathmin gene. Not only did these mice show no fear in open spaces, but they failed to learn classically conditioned fear responses.
1. Shumyatsky, G.P., Malleret, G., Shin, R.M., Takizawa, S, Tully, K., Tsvetkov, E., et al. (2005). Stathmin, a gene enriched in the amygdala, controls both learned and innate fear. Cell, 123, 697-709.
1 Comment
jejabe13 · December 8, 2006 at 1:00 am
While the research as a whole is quite interesting, I especially found the last part of the post curious. If the rats without stathmin were not able to learn classically conditioned fear responses, what does this say about classical conditioning? It seems learning associations between stimuli, at least in this case, is more complicated than CS+US–>UR/CR. Is there an interplay between the type of emotion, i.e., fear, and the learning itself? What do the researcher’s make of this finding?
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