The brain is a surprisingly plastic organ, often able to in essence rewire itself when parts of it are not working the way they should be. A series of studies done at the UCLA Brain Research Institute — the most recent results of which were published in the journal Proceedings of the National Academy of Sciences on August 2, 2010, and detailed in a LiveScience article on August 9, 2010 — demonstrated that rats whose fear-generating mechanisms were disabled could still manage a fear response; another part of their brains had taken over the job.
The Amygdala and Memories of Fear
While the fear response is complex and registers in many areas of the brain, the region known as the amygdala is responsible for both storing the emotional memory of the fear response and for reacting to danger. This is true in the brains of both rats and humans. Earlier research at UCLA had demonstrated that rats with damaged amygdalae still showed relatively normal fear responses; the most recent studies pinpointed the reason.
The Bed Nuclei Step in and Take Over
In the experiments, rats were conditioned to form fear responses to a cage that repeatedly gave them electric shocks. After a few trials, rats with normally functioning brains showed obvious fear when confronted with the cage, often freezing in terror. But curiously, when researchers disabled some of the rats' amygdalae — by introducing lesions — the rats still showed a largely normal fear response.
It was only when lesions were introduced on the amygdala and the bed nuclei — a region of the brain that shares many connections to parts of the brain also connected to the amygdala — that the rats became unable to respond to danger or form fear memories. Additionally, when lesions were created only on the bed nuclei and not the amygdala, the rats fear responses were normal, leading researchers to conclude that the bed nuclei served as a kind of "backup system" for the amygdala, only kicking in when amygdala function was impaired.
Applications for Memory Loss
These studies, along with others performed on other regions of the brain, are still in early stages, but clearly demonstrate that brains have the potential to be flexible and form "work-arounds" when certain parts are damaged. Researchers hope that by understanding how this brain compensation works, they can learn to control and channel it in ways that could help people who have suffered strokes, Alzheimer's, or other types of memory loss.
Sources:
Poulos, Andrew M. et al. "Compensation in the neural circuitry of fear conditioning awakens learning circuits in the bed nuclei of the stria terminalis". Proceedings of the National Academy of Sciences. August 10, 2010
Rettner, Rachael. "Brain Has Backup Circuit for Fear". LiveScience. August 9, 2010
Jenny Ashford - Jenny Ashford is a writer and graphic artist from central Florida. Her main area of interest in her Suite 101 articles is science, with a ...
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