The human brain is composed of the most amazing stuff and is the most complex material in the universe. It is three pounds of near jello consistency that is comprised of 100 billion nerve cells (neurons). These cells have long extensions that go from the brain as far as the internal organs. They also have shorter extensions that are the business ends (dendrites, Greek= treelike). Our thoughts originate where two dendrites connect; they are living computer chips. The brain through these connections is essentially a binary computer. The truly amazing fact is that each of the 100 billion nerve cells can have as many as 10,000 connections. This equates to more connections than the number of minutes the Earth has existed. Big computing numbers give big computing capacity, which allows the human mind to do incredible tasks. It allows me to remember back to events in kindergarten.
The human brain weighs more than other species except for elephants and whales. Further, the design of the human brain is remarkable; it has hills and valleys producing twisted ridges on its surface called convolutions. The brainy ridges become more pronounced in higher primates and are associated in humans with intelligence.1 This seemingly unlikely association has a good anatomical basis, brain cells form the gray matter of the brain and are located on the brain’s surface. Convolutions increase the surface area of the brain, ergo, the more surface area, the more brain cells.
In the past, it was considered that unlike most other areas of the body, adults only lost nerve cells as we aged (rather depressing). However, the good news is that our grownup brains have cells that die but form new nerve cells as well.2
The aging brain decreases in size, especially in the frontal lobe areas and the hippocampus at the base of the brain. The hippocampus decreases about 1% yearly after age 60 years.3 This normal aging of the brain is very important because the functions of the hippocampus allows one to lead an independent life. Actually, there are two of these small structures located at the base of the right and left sides.
They are small each averaging only the weight of a nickel but critical to overall functioning. The Hippos retain very recent memory such as did I take my meds a few minutes ago? Did I turn off the stove? Where did I put my glasses? In other words, it allows us to live independently, thank goodness. Memory can be correlated with Hippo volume.4 Another necessary function the hippo is spatial reasoning. When one goes into familiar places, the Hippo recognizes and lets one know where they are located. It is a living Garmin GPS. When going somewhere, it guides one back home. Also, the relationship may or may not be causal but people with major depression disorders have smaller hippos.5
The brain ages just like the rest of the body and the process changes mental functionality. None are exempt; we are all on the same conveyor belt. Normal brain aging allows independent living until the extremes of age. Thought processes gradually are slower, tending to be noticed when rapid decision making is necessary. Memory tends to be blunted especially in finding the right word or naming objects. It is normal aging if the forgetfulness is temporary. It is the “it’ll come to me after a little while” episodes that signal normal aging.
The balance center is located in the back of the brain at its base. Balance is less secure in the aging brain leading to a greater numbers of falls. Falls occur in one of every three people over 65 years, and one in three who falls will have serious injuries.6 Falls are the most common cause of death from injuries in the elderly. In 2013, over 25,000 deaths from falls were recorded. Falls generally are preventable with balance and strength training.
There are ways to allow your brain to age more slowly which we will discuss in future blogs.
- Luders E, Narr KL, Bilder RM, et al. Mapping the relationship between cortical convolution and intelligence: effects of gender. Cerebral cortex 2008;18:2019-26.
- Inta D, Cameron HA, Gass P. New neurons in the adult striatum: from rodents to humans. Trends in neurosciences 2015;38:517-23.
- Erickson KI, Prakash RS, Voss MW, et al. Aerobic fitness is associated with hippocampal volume in elderly humans. Hippocampus 2009;19:1030-9.
- Erickson KI, Voss MW, Prakash RS, et al. Exercise training increases size of hippocampus and improves memory. Proceedings of the National Academy of Sciences of the United States of America 2011;108:3017-22.
- Bremner JD, Narayan M, Anderson ER, Staib LH, Miller HL, Charney DS. Hippocampal volume reduction in major depression. The American journal of psychiatry 2000;157:115-8.
- Sterling DA, O’Connor JA, Bonadies J. Geriatric falls: injury severity is high and disproportionate to mechanism. The Journal of trauma 2001;50:116-9.