Cell replacement and the brain

[GreenDestiny]

I somewhere read the argument that the cells of the human body are continuously being replaced by new ones, so that after some period of maybe 7 years you have a completely new body. Because of this, the argument goes on, the world can't be completely material and there has to be something like a soul, because your body has been exchanged but you are still the same person.

 

What do think of think of this argument?

I also read somewhere that brain cells are indeed the only cells that are not being replaced (and that explains why brain damage is permanent).

 

Can someone clarify this?

Do you have the same cells in your brain from birth to death?

 

Another thought I had was that maybe cells could be replaced, but the information that is carried in the brain could stay the same - so that the "I" is something like the ongoing state of the information in your brain.

 

But if the cells themselves stayed the same, this argument wouldn't work anyway...

[The Brind]

I somewhere read the argument that the cells of the human body are continuously being replaced by new ones' date=' so that after some period of maybe 7 years you have a completely new body. Because of this, the argument goes on, the world can't be completely material and there has to be something like a soul, because your body has been exchanged but you are still the same person.

[/quote']

 

Here's a relevent link...

http://cgee.hamline.edu/see/questions/dp_cycles/dp_cycle_nutr.htm

 

What do think of think of this argument?

I also read somewhere that brain cells are indeed the only cells that are not being replaced (and that explains why brain damage is permanent).

 

The brain has only a limited ability to make new neurons. And yes this does explain why brain injuries are permanent (note - sometimes other areas of the brain can take over the function of damaged areas especially if the brain damage occurs when you are young)

 

Can someone clarify this?

Do you have the same cells in your brain from birth to death?

 

Yes you do have the same cells in your brain from birth to death and at the same time no you don't...

 

Confused?

 

The cells themselves are being constantly repaired and renewed so the same cell that you had when you were born is not made from the same atoms and molecules...

 

Imagine a wall....

 

Now one by one replace the bricks in the wall....

 

Once you have finished you can ask yourself....

 

Is this the same wall that I started with?

 

The answer is both yes and no depending on how you look at it...

 

People are like that wall and so are cells... in fact many so called "things" are like that wall if you think about it...

 

Another thought I had was that maybe cells could be replaced' date=' but the information that is carried in the brain could stay the same - so that the "I" is something like the ongoing state of the information in your brain.

 

But if the cells themselves stayed the same, this argument wouldn't work anyway...[/quote']

 

Correct. Kind of... The cells in your brain retain enough of their structure and function so that information continues to flow through the brain without any drastic changes...

 

Hence self identity is preserved... but remember self-identity or the "I" is not a solid unchanging thing... the patterns of information processing that underwrite the self and self identity are constantly changing as well...

 

So to go back to your original paragraph...

 

the world can't be completely material and there has to be something like a soul' date=' because your body has been exchanged but you are still the same person.

[/quote']

 

You are not still the same person.

 

The matter that constitues the brain is constantly changing and the information processing patterns that constitue the self are as well..

 

If you don't take my word for it... go read a really old school jotter and see how much it feels like it is the same "you" speaking that you like to call "me" now!

[Skye]

Well one thing to remember is that those cells that are being 'replaced' are being replaced by cells formed by the division of existing cells. Another is that cells are replacing many of their constituent molecules constantly. Most important though, is that order at the level which we recognise, such as the brain, is constantly being reinforced. While the parts may change the machine stays much the same.

 

I also read somewhere that brain cells are indeed the only cells that are not being replaced (and that explains why brain damage is permanent).

There's been some small amount of cell division shown to happen, in rats mainly, but also more tenuous evidence for it in people. However, people can recover from damage to the brain, to some extent, because the existing neurons can still migrate within the CNS and form new connections. The limited ability of brain cells to divide certainly limits the brains ability to heal though.

Do you have the same cells in your brain from birth to death?

If I recall correctly, cells in child's brain cells continue to divide as they grow and develop. In adults, aside from the small number I mentioned, division stops and you have the same cells thereafter.

[The Brind]

After digging around I came up with this article from respected science journalist John McCrone...

 

http://www.sci-con.org/articles/20040601.html

 

The whole brain replaced every month... that's kinda scary in some ways!

[GreenDestiny]

Indeed!

 

"This kind of topsy-turvey picture can only be resolved by taking a more holistic view of the brain as the organ of consciousness. The whole shapes the parts as much as the parts shape the whole. No component of the system is itself stable but the entire production locks together to have stable existence. This is how you can manage to persist even though much of you is being recycled by day if not the hour."

 

It'll be interesting when someone find out more about it... 'No component itself is stable, but the system as a whole is' is not really a very detailed explanation.