Life of Brain: How the Brain Matures over the Lifespan

by Alena Deuerlein

M.Sc. (Interdisciplinary Neuroscience); Master’s student of Psychology, Frankfurt am Main

We age every day. Most of the time we don’t realize it. But the aging process is a relentless force of nature. What happens in our brains as we get older? Each stage in life brings about different neuronal changes, from infancy to old age.

Photo by Colin on Unsplash

The behavior of a newborn baby is mostly dominated by reflexes. Early in life, the baby’s primary concern is to survive by crying, eating, sleeping, crying, eating, sleeping. While infants’ behaviors seems exceedingly simple, their brains undergo an incredibly complex period of development.

On a neuronal level, the brain produces more than a million neural connections each second. Contrary to common belief, the infant brain has more neurons than the adult brain. A baby is born with all the neurons it will ever need or have. In the first three years, a child’s brain has up to twice as many synapses as it will have in adulthood [1].

The cerebellum triples in size within the first year [2], which may be related to the rapid development of the infant’s motor skills. As the visual areas of the cortex grow, the infant’s visual ability is strengthened.

During early childhood, the brain produces more synaptic connections than it uses and surplus neuronal connections are gradually eliminated. These processes are called blooming and pruning. True to the motto Use it or lose it!, synapses that are rarely stimulated lose their connections and those that are regularly stimulated become “hard wired” and are strengthened. The development of the brain and the way synapses form is influenced by many factors, including a child’s relationships, experiences and environment. Children growing up in a loving and caring environment are not only healthier and happier during adulthood than those experiencing neglect and lack of affection [3], but may also display structural brain differences, such as bigger brains [4].

In a healthy child, the brain volume will double by the age of 3, and more complex skills such as memory, language, and thinking improve.

The final growth spurt of the brain progresses from the back of the brain to the front. During late childhood, the cerebellum, which controls physical and motor coordination, develops first.

Early adolescence is characterized by a set of changes as a result of emerging puberty, including behavioral, physical and neuronal changes. This is the time in a teenager’s life when suddenly the parents seem exceedingly irritating and clingy, as if they go out of their way to act as embarrassing as possible and start fights for no reason. The teen years are arguably as stressful for the parents as they are for the adolescent. The adolescent brain pours out a cocktail of hormones, including stress hormones, sex hormones, and growth hormone, which in turn influence brain development. In adolescent boys, the production of testosterone increases 10 times [5].

Linked to the hormonal changes that are taking place are neuronal changes. The last area to be fully developed in the adolescent brain is the frontal cortex, which is important for skills such as emotion regulation, impulse control and decision-making. This will probably ring a bell, since these are the skills teenagers are known to have the most problems with during puberty.

While a healthy adult and with a fully developed frontal lobe knows when to say no to peer pressure and risks, teenagers act more like a Ferrari with weak brakes. This causes teens to take undue risks and engage in dangerous behaviors such as unprotected sex and drug use. You could think of the teenager’s brain as an entertainment center without a remote control. The frontal lobe will only fully be matured by the mid-20s.

By roughly 25 years of age, brain development is thought to be fully completed. Congratulations, you’re an adult now – at least on a neuronal level. It’s mostly downhill from here.

Or is it?

Brain functioning tends to slow down in the later stages of life in several ways. First, the brain decreases in size and becomes slower at processing incoming stimuli. This decrease in brain volume is most often observed in the prefrontal cortex and hippocampus [6]. Movement, speech, reaction time, and overall processing skills are reduced. Furthermore, aging is a major risk factor for non-normative cognitive changes in adulthood, including mild cognitive impairment, Alzheimer’s disease, Parkinson’s and Huntington’s disease.

While younger adults can perform tasks using less cognitive effort, older adults must compensate for brain slowdown and shrinkage by using multiple brain regions and more cognitive effort for such tasks [7]. Although general trends do exist, there is a large degree of individual variation in how the brain ages, with many displaying remarkable cognitive plasticity and flexibility well into their late adulthood years.

Photo by Cristian Newman on Unsplash

Amid the bad news concerning neural and cognitive deterioration that occurs with age, there is some good news. Emerging evidence suggests that a healthy lifestyle may decrease the rate of cognitive decline and help delay the onset of cognitive symptoms [8]. Furthermore, physical exercise and cognitive training may improve cognitive function in older adults.

While getting older can be daunting, it is important to keep in mind the merits old age can bring: wisdom, happiness, patience, more time for loved ones, less social pressure, and senior discounts. Every cloud has a silver lining.

Brain aging is inevitable and for the most part unstoppable. However, the biological age depends upon the genetic code, not the passage of time. As Mark Twain once said, age is a question of mind over matter. If you don’t mind, it doesn’t matter.

Sources:
[1] https://bit.ly/1h3l16m
[2] https://bit.ly/2Q7g3du
[3] https://bit.ly/2EV7UqE
[4] https://dailym.ai/2QW8QCq
[5] https://bit.ly/2PNCVDj
[6] Rodrigue & Kennedy, Handbook of the Psychology of Aging, 2011
[7] Cappell, Gmeindl, & Reuter-Lorenz, Cortex, 2010
[8] Murman, Seminars in Hearing, 2015

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