PET scans show that the rate of blood flow in the gray matter of the front cortex starts to lessen around age 50. There is a reduction in the efficiency of energy production in the mitochondria of brain cells with age. (Carper, Jean. Your Miracle Brain. NY: HarperCollins Publishers, Inc., 2000, pp 17-18)

Studies: aging humans who consumed more omega-3 fatty acids had increased gray matter brain volume. Most new tissue development was observed in the portion of the brain associated with happiness. (Sarah M. Conklin, PhD. High -6 and Low -3 Fatty Acids are Associated With Depressive Symptoms and Neuroticism. 2007.)