Brain Power by Susan Pataky Do you feel as if your brain is turning to mush with each passing year? Is it age or is is stress?  Many neurologists believe that over time the structure of the brain grows lighter(shrinks slightly) and loses approximately one million neurons a year as it ages. Is senility really the result of this neuron loss and the decaying brain? If we all lose this many neurons annually why is it that only some of us become senile or worse are diagnosed with Alzheimers? Animal research shows that the brain grows new connections as we age thus, perhaps, compensating for the neurons that have died. Another interesting fact is that no two brain cells actually touch. Dendrites(derived from the Greek word for "tree") reach across a synapse(gap) via hundreds to thousands of hair-like filaments like intertwining branches. Chemical signals can be then sent to one neuron to another. There is currently no research as to why some neurons grow fifty dendrites vs others which grow ten thousand. One thing is known, that chemicals are involved. Again we turn to the stress hormones namely cortisol. We know that stress effects every physiological system including down to the cellular level. Thus contributing to just about every disease state. A continued state of stress means excess cortisol and for the brain that means shrinking neurons. In addition  research shows that in the presence of excess cortisol the neurons actually change shape. Any feeling of stress that is not managed and dealt with builds and if your life has you always under stress it then becomes chronic. This can make the most stable person feel overwhelmed and pushed to the breaking point. The good news is that the brain is very resilient and once stress is eliminated the neurons grow back. A Japanese study showed a decrease in serum cortisol during yoga exercise. In 2003, at the 85th Annual Meeting of The Endocrine Society it was announced that cortisol, a hormone linked to stress, is significantly reduced in people who practice yoga. These findings have helped pave the way for therapeutic applications of yoga. Interestingly, research with rats, done by Marian Diamond at Berkeley, has helped confirm that there is also a physiological component to brain shrinkage and brain growth. The result showed that the rats when lonely, islolated, and deprived of social interaction, began to develop shrinking cortexes and a loss of dendrites. Conversely if the rat was put back into social settings with lots of stimulation theirs brains began to grow new dendrites and expand. This scenario is easily translated to human existence.