Me and my brain: Growing old together

Growing old is natural. Old age is yet another life stage with its own unique challenges and opportunities. It seems though that we are still unsure about what it actually means to grow old. Across cultures, old age is portrayed along themes of both wisdom and mental decline. But how can we grow wiser if our brain declines? Are these representations of aging grounded on truth or are they just myths being perpetuated over and over? And how do we know if the changes we notice in our aging brain are normal or a warning sign of incipient dementia?

Alas, we have now entered the public discourse about cognitive aging; a discourse which is often rife with myths, half-truths and oversimplification. It is easy to dismiss any cognitive problem as part of normal aging or to interpret any cognitive change in old age as a sign of dementia. People tend to get caught up in either of these two, rather extreme, positions as there is a widespread lack of information about the actual process of cognitive aging. To put it simply, nobody tells us what to expect from our brain as we get older!

Let’s take a journey into the aging brain. As we grow older, transmission of information in our brain slows down and some neurons are lost however existing neurons continue to form connections throughout our lifetime. Our sleep patterns also change. The amount of deep sleep and REM sleep (the stage of sleep related to dreams and consolidation of newly-learned information) decreases. It is expected that these biological changes will also lead to changes in the way our brain works. Let’s see now how aging affects the different functions of our brain in detail.

Processing speed is the speed with which our brain analyzes information. Its decline begins at the third decade of our life and continues throughout the lifespan. That means that my students can definitely read faster than me but I won’t fret a lot about that. As we age, we can still read, write and think albeit a bit slower than our younger selves.

Attention is our ability to focus on important information. There’s little decline of attention in old age and that decline is limited to more complex forms of attention. One example is selective attention which is our ability to focus on specific information while ignoring irrelevant information. A good everyday example of selective attention is sitting in a caffe and listening to our friends while ignoring the conversations in neighboring tables. Another form of complex attention is divided attention which is the ability to focus on multiple tasks simultaneously. Those of you that enjoy talking to the phone while cooking will have a good understanding of divided attention!

Memory is our ability to remember things. And there are a lot of myths about memory in old age such as the sweeping generalization that all older adults have memory problems. The truth, as usual, is more nuanced and to get to it we have to look into the different types of memory. A basic distinction is between explicit memory i.e., our ability to consciously recall facts and events and implicit memory which is essentially knowing how to do things (e.g., riding a bicycle or singing “Happy Birthday”). Implicit memory remains unchanged across the lifespan and, maybe, we tend to associate old age with wisdom since the older we get, the more skills and abilities are stored in our implicit memory. Concerning explicit memory, we must delve deeper into its different sub-categories. Our semantic memory i.e., general knowledge, declines in late life. At the same time, our episodic memory i.e., memory of events, declines throughout life. Maybe that’s why we can never remember who was in that graduation ceremony!

Language abilities remain mostly unchanged with a few exceptions. Verbal fluency (e.g., naming as many words that start with the letter “a” as possible) declines with age. Also, the ability to name objects can decline after the age of 70. On the contrary, our vocabulary can keep improving throughout the lifespan.

Visual abilities encompass our ability to process and work with visual information. Visual constructive abilities (e.g., assembling flat-pack furniture) gradually decline with age. On the flipside, there is no decline in visuospatial abilities i.e., our ability to perceive 3-D space and recognize objects and people.

Executive function refers to capacities that allow a person to successfully engage in independent, appropriate, purposive, and self-serving behavior. Abilities such as concept formation, abstraction, mental flexibility, response inhibition, and reasoning with unfamiliar material decline with age. Abilities such as reasoning with familiar material, describing the meaning of proverbs and detecting similarities remain unchanged.

Moving beyond specific cognitive functions, another way to understand cognitive aging is through the lens of Crystalized Vs Fluid Intelligence. Crystalized Intelligence comprises skills, ability, and knowledge that is overlearned, well-practiced, and familiar (e.g., vocabulary/ general knowledge). Fluid Intelligence comprises abilities involving problem-solving and reasoning about things that are less familiar and are independent of what one has learned (e.g., working with unfamiliar information, learning new skills). One could argue that we get wiser as we age but we lose some of our ability to adapt to new circumstances.

At this point, I hope I have painted a somewhat comprehensive picture of the complex nature of cognitive aging. And I apologize in advance because I am going to add to that complexity. While the cognitive changes I mentioned are to be expected, they do not appear on all individuals at the same age and with the same intensity. Aging is as unique as each individual and the interplay between age and cognitive abilities will differ between individuals. Which begs the question of how do we even begin to define healthy versus pathological cognitive aging. I promise to devote a whole article to that very important question but for the time being I will offer a brief explanation. We tend to define healthy cognitive aging based on cognitive performance that is in line with what is expected based on the age and education of the individual and also based on the individual’s ability to function autonomously in their daily life. For now, I hope I have succeeded in making you think of aging as a complex and individual procedure and as a life stage that is as normal and unique as any other period of our lives.