Odor and the Brain
Can a few sniffs separate those who become demented from those who do not?
Some researchers think so. The reasons why can tell you a lot about how your brain and body work – and ways to get them to work better.
What Was Found?
It’s been known for a long time that olfactory nerves – the stuff that gives you smell – and a very large part of taste – completely regenerate in six to eight weeks. That’s right. Unlike most of the nervous system, which simply remakes its cells from the ground up, olfactory nerves die. Then new cells produced from special stem cells take over – and help you smell and taste.
So researchers took a group of elderly – people 65 and such vintage – and had them take five sniffs. Good testers could identify four or five common odors; worst testers zero or one.
Then they waited.
The people who couldn’t smell well had much higher rates of cognitive impairment and dementia years later.
Why Is This So?
The body has to regenerate to survive. If I can’t do that properly, it loses critical adaptability – and dies.
Olfactory nerves have to completely regenerate. If they don’t you can’t smell. And taste also goes down the tubes.
People who can’t smell (anosmia) will tell you that food is often “tasteless.” So is much of the rest of life. They often feel pretty miserable.
And their health statistics are not great. If your olfactory nerves can’t regenerate, what happens to the rest of you?
It’s not surprising that lack of smell indicates a lot of potential future health problems. But there’s much more to smell than just how well you remember or survive.
Can My Liver Smell, Too?
In a real sense, yes. Liver cells have some of the same receptors – the complex sensors used to tell tastes and smells apart – that olfactory nerve cells do.
And they use them in a similar way. They help identify foreign molecules. Much of the time, after identification, the strange molecules are “detoxified” – reduced to harmless components.
What’s “smell” doing inside your liver? And for that matter, the lungs and other organs? Well, your body does not know it’s supposed to use smell receptors only in your nose. It puts them to very good use elsewhere.
Just as there are light receptors in the eye that have nothing to do with vision. They don’t send their signals to the visual cortex. Instead, they go to the suprachiasmatic nuclei – a group of master clock cells in your brain. These light receptors let you know where your body is in the 24 hour day and the 365 day year. They help time your life.
Life without good internal timers is difficult. Just ask blind people who lack them – about half.
If you have an inner clock which can’t get reprogrammed by light, you are in trouble. Let’s say you have an inner 25 hour cycle.
So you go to bed tonight at 10 PM, tomorrow at 11 PM, the next night at midnight – all through the year.
That makes work and social life very, very difficult.
You need to have functioning receptors so your body can regenerate properly. Fortunately, you can put them to use even when an injured body can’t.
Can Smell Cells Help Overcome Spinal Injury?
They just have. A Polish patient with cuts in his spinal cord was paralyzed. He could not walk. A joint British-Polish team tried to fix that.
They grew up stem cells from his own body. Then they put them back into his spinal cord.
That was not sufficient, however. To overcome spinal cord injuries, you have to get cut cells to connect to one another. That has always proven very, very tough.
In this man’s case, they used a novel plan – they transplanted his olfactory bulb.
In other words, they took out one of his smell organs, and put parts of that on top of his shredded spinal cord.
Why? Because olfactory nerves have to regenerate. That’s what they do – and quickly. And as hoped, some of the olfactory cells helped the new stem cells do just that. Together they “bridged the gap” between disconnected nerves.
Now, after very intense physical therapy for a very long time, this man can walk a little bit. He hopes to get much better, working at it five hours a day with physical therapists.
Will this treatment eventually help millions with spinal cord injuries? It’s way too early to tell. But it does tell us about the great powers of smell – and of smell cells.
Smell is vastly underrated. But what the new work with olfactory cells and their receptors tells us is more underrated still – that your whole body is a continually regenerating information system.
You are rebuilt all the time – inside and outside, and from the ground up.
That has immense implications for lots of things: how you live; what keeps people alive; how we practice medicine.
Just as smell can involve much more than smell and taste, so does light involve much more than seeing. All these systems are connected. It all works together.
And different lifestyles provide very different regenerative outcomes. Walk through a condemned car park for 20-30 minutes, and you’ll do more than rejigger your sense of smell.
You’ll grow new brain cells. In sleep. Memory cells you will use soon.
How you live determines what you become. The real health question is – what can I do to regenerate better?
It’s time we all started asking that question – of ourselves and our families.
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