As people age, their senses change and dull. But why does this happen? In this lesson, we'll examine the changes in the brain and nervous system that cause a decline in sensory perception in later life.
Marie is in her 70s, and she loves being retired and having time to socialize with all her friends. But she's also noticed some problems. Lately, her hearing isn't as good as it used to be. She has to turn the TV volume up, and having a conversation in a coffee shop or restaurant is tough because she can't hear her friends over the background noise.
Marie is in late adulthood, or the time of life after age 65. During this time, the body is going through changes. Sensorimotor skills, or those relating to our relationship with our environment, tend to decline as we age, so many people in late adulthood have problems with their senses, like Marie, and with the movement of their bodies. Let's look closer at changes in sensorimotor skills and how they can impact a person's day-to-day life.
Marie is having issues. Her hearing is getting bad, and her eyesight isn't as good as it used to be, either. She is worried that something serious might be wrong.
What Marie is experiencing is a normal part of aging. As we age, our sensory input, or information sent to our brain by other parts of our body, declines. Think of the word 'senses' and you can remember 'sensory,' and that's really all it is: information from all five of our senses.
You can also think of the word 'input' to understand how sensory information works. Our senses send information to our brains; it is input provided to our brains about our environment and our role in the environment.
So when Marie can't hear or see as well as she used to, it's part of the normal decline of sensory input in aging adults. But what causes this decline?
There's a part of the brain called the sensory cortex whose entire job is to process sensory information as it comes in. The sensory cortex figures out what's going on and then sends messages to other parts of the brain to react to that information. As we age, the sensory cortex begins to degenerate. That is, the brain tissue in that part of the brain begins to break down and not work as well.
Something else happens, too. The nerve cells, which carry messages from different parts of the body to and from the brain, become slower. Some of them die, which decreases the number of nerve cells, too. As a result, the sensory cortex isn't getting the messages it needs from the nerve cells.
So basically, everything starts to break down, both within the brain and outside of it. As a result, all of our senses gradually decline with age. Marie has noticed that her hearing and vision aren't as good, but she also can't taste things as well as she did, and her sense of smell isn't as strong as it was when she was younger.
The changes in sensory input don't happen overnight. It's a very gradual process that happens over years and decades. Most adults adjust to the minor changes in sensory input very well. It's only when people become very old that the sensory input issues make it hard for them to perform everyday activities.
Remember nerve cells? They connect the brain with the rest of the body. As Marie's hearing and vision decrease, a loss in the number of nerve cells and a slowing down of the nerve cells that survive are partly responsible.
But nerve cells do more than just give information to the brain. They also carry information from the brain to the body. Think of them like a superhighway running all through your body. There are multiple lanes running in two directions on this highway: one running to the brain with sensory input and one running from your brain with motor output, or information sent from our brain to the rest of our body to induce movement.
Just as with sensory input, you can remember motor output by its name. The word 'motor' means 'movement,' and the brain is sending 'output' to the body to move.
Imagine that Marie is sitting on a nice park bench enjoying a sunny afternoon. Suddenly, a Frisbee comes flying towards her. Someone shouts out, 'Watch out!' In this moment, Marie has sensory input from her eyes (which see the Frisbee) and her ears (which hear the warning) traveling along her nerve cells to her brain. They get to the sensory cortex and her brain says, 'Whoa! We'd better do something about this!'
So the sensory cortex sends a message to its neighbor in the brain, the motor cortex, which sends information to her body to move. She can duck so the Frisbee doesn't hit her.
In healthy adults, this entire process of sensory input and motor output takes a fraction of a second. But in Marie and other older adults, the process is slowed down.
Remember that we said that two things happen to nerve cells as we age. They are reduced in number, and they become slower. Imagine the superhighway of nerve cells and that some of the lanes in both directions are closed down. Uh-oh! Traffic jam!
Not only that, but the lanes that are open (that is, the nerve cells that are still working properly) are moving slower than normal. As you can imagine, the reduction in both speed and quantity of nerve cells has an impact on a person's reaction time. Marie might not react to the Frisbee in a fraction of a second; it might take her several seconds instead.
For many things, several seconds is not a big deal. But there are some situations when several seconds can have a big impact. If Marie doesn't get out of the way fast enough, the Frisbee might hit her on the head. That would hurt and might cause a bruise, but chances are that Marie (and the Frisbee) would be okay afterward.
But reaction time can cause deadly problems with regards to things like driving. A slower reaction time (even just by a few seconds) can cause serious accidents. For this reason, some states have adopted additional tests before issuing driver's licenses to older adults.
Late adulthood is the time of life after age 65. During late adulthood, many people find that their sensorimotor skills decline. Sensory input is dampened as people lose the sharpness of their senses. This is caused by degeneration of the sensory cortex area of the brain, as well as the decline in number and speed of nerve cells. In addition, motor output, which occurs from the motor cortex of the brain, is slowed by the decline in nerve cells, resulting in a slower reaction time.
After this lesson is done, you should be able to:
- Identify the time in life known as late adulthood
- Understand the slow down in sensorimotor skills during these years
- Explain how the degeneration of the sensory cortex and nerve cells lead to changes regarding sensory input
- Describe the changes in motor output that occur with age and why these changes occur