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The brain is separated into different regions, and different regions perform different tasks. Well, what are the differences between these regions on the cellular/systemic level. The brain is made up of neurons and other cells, but how come one part is used to process sound and another is used to process, say, smell? Are they like different computer circuit boards - using the same components but are wired differently?

And anyways, why did evolution not come up with a brain that uses the entire brain to process something, would that not be more efficient?

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3 Answers 3

The wiring is different as you mentioned. However, perhaps the most important is the brain knows where it's input is coming from. The brain knows where each fibre innervates and thus can compile and present this data to our conscious mind. We show if we stimulate the brain directly, than we feel a sensation in the part of the body that portion of the brain is responsible for. Plasticity means our brain can change what feeds into where, this is most commonly where we learn a motor skill. If we play the piano for example the part of the cortex feeding to this area increases.

Another way is the type of chemical transmitter and receptor. Dopamine is primarily used for things that cause us pleasure for example. However dopamine can affect our movement if it is secreted in from the substantia nigra, as this feeds into the motor cortex. Furthermore, neurotransmitters can be excitatory or inhibitory and this is an analogue rather than binary signal. All of these fine tune, and the position at which they inhibit and the location and the feedback from which they obtain their signal all indicates from where the brain is getting the information or to what it is responding to.

In summary it is wiring, signalling and location. However the components are incredibly similar but it isn't the small differences that have a profound effect.

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OK, thanks for your answer, but WHY is this more efficient that if they are not separated? Why can't every part of the brain (at least the cortex) perform every function? Or can it? If a part of someone's brain is missing, would the other parts eventually be wired differently to 'replace' the missing part? –  dayuloli Jun 1 '13 at 13:50
    
You have a machine that makes ice cream, a machine that makes bread and a machine that makes cookies. You lose the machine that makes cookies, would you use the ice cream maker or the bread maker? Would they be as good? That's how it works. Parts of our brain are specialised because they adapt as we use them. If we lose one part another part can take over that typically can mimic some of the function, but it isn't as great. If the part is unique then our brain has more difficulty. However it will unlikely be as efficient unless we train it to high degrees. That's a general theory. –  AndroidPenguin Jun 1 '13 at 14:06
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If it wasn't clear why this means we have different regions catering for different things, then it is about efficiency. Using specialised well-adapted equipment is much better than using general stuff for everything. –  AndroidPenguin Jun 1 '13 at 14:07
    
It may be important to point out that different sensations (touch, smell, sight etc) are encoded by means of the same machinery (e.g. neurons, glia) using the same code (e.g. action potentials, calcium waves). If we stimulate a subject's visual cortex using an electrode he will experience visual sensations, although he would not be seeing real things. –  nico Jun 29 '13 at 14:54

We don't know yet in detail how different cortical areas are wired up, so it's difficult to say to what extent the wiring differs. But the overall structure of different cortical areas is remarkably similar, in terms of the layers of cortex and their cellular components.

Certainly the structure of the input is very different between cortical areas, and cortex seems to take great care during development how that input is structured.

We don't know why cortex is parcellated the way it is. But connections within cortical areas devoted to a single "function" are much more prevalent than connections between cortical areas. This suggests two things: many connections are required between neurons processing similar information, which implies that those neurons should be close together, because wire is expensive in the brain (i.e. requires resources and takes up a lot of space); alternatively, maybe the information is easier to process if it's kept physically separated.

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The brain is separated into different regions, and different regions perform different tasks

Not really. This kind of claims stem from the early brain research, where every area was thought to specialize in one particular task. Sure, some categorization is possible (e.g. where the visual input is mostly processed). However, your question is basically an argument that is false.

Just look for example the temporal lobes and compare how the sulcal and gyral areas differ with respect to information processing.

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