BBC - 'Brain decline' begins at age 27

[Hammy070]

http://news.bbc.co.uk/1/hi/health/7945569.stm

Mental powers start to dwindle at 27 after peaking at 22, marking the start of old age, US research suggests.

Professor Timothy Salthouse of Virginia University found reasoning, speed of thought and spatial visualisation all decline in our late 20s.

Therapies designed to stall or reverse the ageing process may need to start much earlier, he said.

His seven-year study of 2,000 healthy people aged 18-60 is published in the journal Neurobiology of Aging.

To test mental agility, the study participants had to solve puzzles, recall words and story details and spot patterns in letters and symbols. The natural decline of some of our mental abilities as we age starts much earlier than some of us might expect

Rebecca Wood of the Alzheimer's Research Trust

The same tests are already used by doctors to spot signs of dementia.

In nine out of 12 tests the average age at which the top performance was achieved was 22.

The first age at which there was any marked decline was at 27 in tests of brain speed, reasoning and visual puzzle-solving ability.

Things like memory stayed intact until the age of 37, on average, while abilities based on accumulated knowledge, such as performance on tests of vocabulary or general information, increased until the age of 60.

Professor Salthouse said his findings suggested "some aspects of age-related cognitive decline begin in healthy, educated adults when they are in their 20s and 30s."

Rebecca Wood of the Alzheimer's Research Trust agreed, saying: "This research suggests that the natural decline of some of our mental abilities as we age starts much earlier than some of us might expect - in our 20s and 30s.

"Understanding more about how healthy brains decline could help us understand what goes wrong in serious diseases like Alzheimer's.

"Alzheimer's is not a natural part of getting old; it is a physical disease that kills brain cells, affecting tens of thousands of under 65s too.

"Much more research is urgently needed if we are to offer hope to the 700,000 people in the UK who live with dementia, a currently incurable condition."

I'm 23 - I anecdotally would agree with the article because I thought I was "mature" at 19, unsurprisingly. But seemed to spurt afterwards. Anyone around the mid-30's age here experience subtle changes after their mid-20s? If so - what examples can you give? And if not, do you engage in any mental challenges (intended or unintended) that could have kept you in your prime?

I am most afraid of mental decline, more than physical. As they say "use it or lose it"...I read somewhere else that education shouldn't stop, and that one should never "graduate" and continue to up their education for as long as possible. Imagine we graduated at 12...with no further challenge, I think we'd get dementia much quicker in society.

 

[HughJass]

How did they know it was biological aging/wear & tear that caused the degeneration in these faculties and not the mindset/outlook of the people involved?

That seems pretty speculative to me.


Hammy: the anxiety over losing your marbles is probably more likely to make it happen before aging does.

 

[CCS]

coincidentally, most people finish school around age 22. Maybe school keeps you fast. But alzheimers does strike very early and just takes many decades to finally take you down. All the thinking in the world won't stop it. Thinking just rewires your brain around the obstacles, but once there are too many of them, you are out of luck.

Lithium can remove the obstacles in your brain, but it can have other side effects too. You can't take lithium your whole life or it will mess you up. Maybe once at age 40 to reset the clock, but depends how fast it dissolves the tangles, and how fast it damages the kidneys.

 

[ali777]

First of all, the article doesn't state anything we didn't already know.

I'm 31, and I still feel relatively sharp. My mental agility MAY have gone down, but I don't notice it.

I'm gonna sound like a wise old man , but there is no substitute for experience. I've noticed that I learn much easier now than I did in my 20s. I think it could be that I have a better attention spun, and with the experience comes the ability to understand things better. I think it's also a case of selective learning, and knowing what is needed for the given task.

On the exercise front, I do challenge myself into solving puzzles, math problems, etc. I take the occasional test just out of curiosity as well. I guess you have to keep all the brain wirings intact for as long as possible. I mean when we learn, the brain lays down certain paths or neurological wirings, ie neuroplasticity. I don't really know when we lose that neuroplasticity, but mine seems to be working OK for now.

I read a book on history of maths. The author said that all the geniuses do most of their work in their mid 20s (too late for us :whistle: ), and later in life they just write and teach. If you think about it, Turing, Einstein, etc did most of their ground breaking work in their 20s. But the likes of Newton kept on going till 70-80.

I'm not sure if this is related, but I remember everything I learnt till 18-19 (I would bet anything you want that I can ace A levels maths and physics). But my uni years are a bit blurred. I did lots of drinking until I was 26, I think alcohol has a big part to play in the gap of information I have.

I feel like saying excessive drinking and smoking are a definite no-no for the brain, but I read that Stephen King used to be so drunk that he doesn't actually remember writing some of his books. I'm not saying everyone can do it, but for an average person, drinking and smoking should be done in moderation, just enough to relax the body and mind.

 

[Old Baldy]

Great! Now I'm a complete dumba**!

 

[CCS]

I'm not worried. With the baby boomers as guinea pigs, I'm sure there will be a cure to alzheimers long before I turn 50.

 

[Bryan]

On the exercise front, I do challenge myself into solving puzzles, math problems, etc. I take the occasional test just out of curiosity as well. I guess you have to keep all the brain wirings intact for as long as possible.

Ali777, here's a little physics (electrical) problem for you: if you have an infinite grid of resistors and all the resistors have the same value (let's say 100 ohms), what value do you measure if you go down and measure the resistance across one of them with an ohmmeter? Assume a two-dimensional grid, stretching out to infinity in all directions.

I have to admit that I don't know the answer to this question, although I've discussed it over the years with friends. Interestingly, some people seem to think that the measured resistance would be ZERO, while others think the answer would be some non-zero value. What do YOU think? I've occasionally tried to see if the resistance appears to be approaching zero, by gradually adding layer after layer of additional resistors after the first one (expanding the grid step-by-step, in other words). But doing those computations is EXTREMELY tedious, and I'm still uncertain whether it asymptotically approaches zero, or some non-zero limit. What do you think? Any ideas on how to solve it EXACTLY?

 

[HughJass]

why would it be zero?


an infinite circuit is an open circuit , so wouldn't you get 100ohms across each resistor?

 

[Bryan]

why would it be zero?

an infinite circuit is an open circuit , so wouldn't you get 100ohms across each resistor?

Huh?? It's a NETWORK of resistors, all connected together in a GRID! So you're definitely going to get LESS than 100 ohms, because there are resistors in parallel with any one resistor, and other resistors in parallel with THOSE resistors, and still more resistors in parallel with THOSE resistors, etc. etc. ad infinitum.

 

[HughJass]

why would it be zero?

an infinite circuit is an open circuit , so wouldn't you get 100ohms across each resistor?

Huh?? It's a NETWORK of resistors, all connected together in a GRID!

oh, so you mean an existing circuit with more circuit's paralleled off of it?


I don't see how it could possibly be zero across any resistor.

 

[s.a.f]

why would it be zero?

an infinite circuit is an open circuit , so wouldn't you get 100ohms across each resistor?

Huh?? It's a NETWORK of resistors, all connected together in a GRID! So you're definitely going to get LESS than 100 ohms, because there are resistors in parallel with any one resistor, and other resistors in parallel with THOSE resistors, and still more resistors in parallel with THOSE resistors, etc. etc. ad infinitum.

Who shot who in the what now? :shock: :tellme:

 

[Bryan]

oh, so you mean an existing circuit with more circuit's paralleled off of it?

I don't know what you mean by that. It's just a GRID of resistors, stretching out to infinity in all directions. Think of a metal window screen, only in place of each little segment of metal wire, there's a 100 ohm resistor. They're all soldered together where they meet at the ends. See what I'm saying? It's an INFINITE GRID of resistors.

 

[HughJass]

Yes I see now.


I don't see how you could ever get zero resistance across any of the resistors, did the people who suggested that give an explanation?

 

[Bryan]

Well, the general idea is that if you start with a finite grid of resistors and then add more and more resistors to the outer edges of the grid so that the grid gets larger and larger, the total effective resistance across the one in the center will steadily drop. It will gradually go down and down and down, without any limit. So with an infinitude of resistors, it will reach zero (according to that point of view).

 

[ali777]

On the exercise front, I do challenge myself into solving puzzles, math problems, etc. I take the occasional test just out of curiosity as well. I guess you have to keep all the brain wirings intact for as long as possible.

Ali777, here's a little physics (electrical) problem for you: if you have an infinite grid of resistors and all the resistors have the same value (let's say 100 ohms), what value do you measure if you go down and measure the resistance across one of them with an ohmmeter? Assume a two-dimensional grid, stretching out to infinity in all directions.

I have to admit that I don't know the answer to this question, although I've discussed it over the years with friends. Interestingly, some people seem to think that the measured resistance would be ZERO, while others think the answer would be some non-zero value. What do YOU think? I've occasionally tried to see if the resistance appears to be approaching zero, by gradually adding layer after layer of additional resistors after the first one (expanding the grid step-by-step, in other words). But doing those computations is EXTREMELY tedious, and I'm still uncertain whether it asymptotically approaches zero, or some non-zero limit. What do you think? Any ideas on how to solve it EXACTLY?

I'll think about it for a bit....

Let me get the picture right... You mean we have a grid, let's say the grid is made up of squares and each side of the square is a resistor???

Here are a few starting points:
http://en.wikipedia.org/wiki/Mesh_analysis
http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws
http://en.wikipedia.org/wiki/Gaussian_elimination

and maybe something useful here: http://en.wikipedia.org/wiki/Wheatstone_bridge

I don't think the answer is zero (my first instinct). For the answer to be zero, you need to have an infinite number of parallel resistors, the limit would be approaching zero. In the grid configuration, we again have infinite number of paths, but the individual paths have increasing resistance. The question is, does the resistance in the Nth path reach infinity before the overall resistance reaches zero.

I'd say the exact solution would require adding one layer at the time. I think there should be an obvious equation for the resistance in the Nth layer.

I've just scribbled something down, and it looks like it goes towards zero... My instinct and my observations are clashing at the moment... I have to think about it. I just don't think it's zero...

 

[Bryan]

Let me get the picture right... You mean we have a grid, let's say the grid is made up of squares and each side of the square is a resistor???

Yes. Exactly.

I'd say the exact solution would require adding one layer at the time. I think there should be an obvious equation for the resistance in the Nth layer.

I've just scribbled something down, and it looks like it goes towards zero... My instinct and my observations are clashing at the moment... I have to think about it. I just don't think it's zero..

The problem's a b**ch, isn't it?

 

[ali777]

On the exercise front, I do challenge myself into solving puzzles, math problems, etc. I take the occasional test just out of curiosity as well. I guess you have to keep all the brain wirings intact for as long as possible.

Ali777, here's a little physics (electrical) problem for you: if you have an infinite grid of resistors and all the resistors have the same value (let's say 100 ohms), what value do you measure if you go down and measure the resistance across one of them with an ohmmeter? Assume a two-dimensional grid, stretching out to infinity in all directions.

I have to admit that I don't know the answer to this question, although I've discussed it over the years with friends. Interestingly, some people seem to think that the measured resistance would be ZERO, while others think the answer would be some non-zero value. What do YOU think? I've occasionally tried to see if the resistance appears to be approaching zero, by gradually adding layer after layer of additional resistors after the first one (expanding the grid step-by-step, in other words). But doing those computations is EXTREMELY tedious, and I'm still uncertain whether it asymptotically approaches zero, or some non-zero limit. What do you think? Any ideas on how to solve it EXACTLY?

I'll think about it for a bit....

Ok, I cheated....

http://www.geocities.com/frooha/grid/node2.html

Here is more detailed answer: http://arxiv.org/pdf/cond-mat/9909120v4
He specifically gives the answer for adjacent nodes, ie, resistance of one resistor.

there is simple solution: http://stevensholland.com/challenge-pro ... 19th-2007/ TBH, this simple solution doesn't make sense to me. I think he stumbles across the solution, rather than giving a proper explanation.

 

[Bryan]

there is simple solution: http://stevensholland.com/challenge-pro ... 19th-2007/ TBH, this simple solution doesn't make sense to me. I think he stumbles across the solution, rather than giving a proper explanation.

It doesn't make sense to me, either, but I'm going to have to study it more carefully. Thanks for finding this stuff!

 

[Old Baldy]

Bryan and Ali: Correct me if I'm wrong but in the simple solution isn't the guy saying there is always a "pure" 25 percent branching of (1) the current coming "in" then (2) branching "out" towards the other four corners of the square? And in that way the current keeps perpetually branching out into infinity (i.e., with zero resistance overall)?

If so, aren't we assuming a possibility that is akin to a perpetual motion machine?

I suppose, in a "perfect" situation where resistance is complete and nothing impedes the flow of electicity, the answer is zero. It's zero at the beginning and zero at any point in the infinite grid.

What would happen if we folded the infinite grid back onto itself in a round ball type of shape? The resistance would be 100 percent then wouldn't it (i.e., in a "perfect" situation)?

If the answer to the "round ball" example above is 100 percent resistance, wouldn't the infinite grid example necessarily have to be zero resistance?

 

[ali777]

Bryan and Ali: Correct me if I'm wrong but in the simple solution isn't the guy saying there is always a "pure" 25 percent branching of (1) the current coming "in" then (2) branching "out" towards the other four corners of the square? And in that way it keeps perpetually branching out into infinity (i.e., with zero resistance overall)?

If so, aren't we assuming a possibility that is akin to a perpetual motion machine?

I suppose, in a "perfect" situation where resistance is complete and nothing impedes the circuit, the answer is zero.

That branching is current, not the resistance. The current after n nodes would be (1/4)^n and will very quickly decrease in value.

I can see how the current going in would be equally divided into 4. Because it's an infinite field, the resistance is equal in all the directions. Likewise I can see how the current coming out would be equal from all 4 directions. I can understand superposition as well.

The problem is, the current that goes in, and is divided into 4, loops back to the same point and will have a negative value. The simple assumption that all we get is 1/4A at that point is not true. I mean, all the currents that will loop back into the same point are ignored. There is going to be an infinite number of currents coming back.

If I ever have free time, I will write a program to simulate the circuit.