Rats are social and territorial animals and when one rat is introduced into the cage of another rat, they will quickly establish who is dominant ? usually the home cage rat wins. Experimenters tip the scales in favor of the home cage rat by using an older or sometimes larger species so that the he is guaranteed to be the bully and the intruder, the victim.



Neuroscientists use this paradigm to study stress because it closely approximates the kinds of stress imposed upon us humans. We see this type of behavior in people throughout much of childhood and early adult life ? from the playground to the office.

Many experiments have shown that intense stress can be bad for a part of the brain called the hippocampus. This brain region is involved in learning and memory and also plays a role in controlling your response to environmental stressors. This is also a brain region that is continually undergoing remodeling.

Neurons (brain cells), are always being born in this region and integrated into the hippocampus. At the same time other older neurons are dying and being replaced. The new neurons come from a special type of cell, called stem cells that acquire different specializations. This happens for different cells all over the body ? in the brain it is called neurogenesis.

The new study showed that bullying, or stressing, rats did not affect the overall rate the new neurons were born at ? but it did affect how long those new neurons survived. Stress decreased the life span of the new neurons so they were not fully integrated into the hippocampus.

There is also a lot of human data that a smaller hippocampus gives you better odds for getting depressed and that stress itself can shrink your hippocampus.

Before you get to worried about your kids getting picked on at school, there is no real data that these types of childhood stressors have any long term effects in people. It typically takes a major stress, like constant emotional or physical abuse at home ? the kind where social service comes knocking on your door.

We seem to be better protected than rats, probably because we have a much better chance of recovering from these little playground confrontations. We usually realize our self-value as we grow up and aren't overly stressed out in a way that does us long term harm.

Still, decades of exposure to a stressful environment can take its toll. If you continually experience stress on the job and bring it home to your kids ? you are not doing either one of you any good.

Not only is stress bad for the brain but many other studies show its negative affects on the cardiovascular and immune systems as well. At some point you have to ask yourself if its really worth it.

Copyright (c) 2007 The Brain Code LLC