Tell Me About the Brain

In a post on a different subject, it was mentioned that the prefrontal lobe of the brain is, in short, where our conscience resides? In other words, the thought processing of right and wrong is conducted here? (Somehow, I never learned this along the way.)

What are the other sections, and what do we know goes on where?

Unless things have changed a lot in the past 20 years or so, that’s oversimplified. The prefrontal lobe has alot of functions, including acting as a sort of mediation centre between various other parts of the brain. It is particularly important in impulse control, essentially mediating between the “higher” brain centres and more “primitive” centres. The prefrontal area also plays a major role in making comparative judgements.So someone with damage to the prefrontal area is likely to lack impulse control and to make really poor judgements, and to that extent that may appear to lack a conscience because they will act on their desires and make bad decisions far more readily than normal people .

However the prefrontal lobe isn’t , as far as I am aware, actually involved in processing right and wrong. It’s just the first check in the system that stops you doing the wrong thing immediately the opportunity arises and also an area that evaluates judgement. Other areas are responsible for evaluating whether the behaviour is right or wrong and whether the impulse is worth acting upon after that analysis.

It’s complicated.

Very complicated.

Anyone who gives you a nice, clear answer to “Where is mental function X in the brain?” is bullshitting.

Really. No-one understands it very well. We have mountains of information, but quite a bit of it is contradictory, and no very clear overall picture emerges. Certainly categories from “folk” psychology, like conscience, do not map at all well onto brain structure. Even categories from scientific psychology (such as episodic memory, or central executive) do not seem to map onto it very well (which does not mean that those functions are not real). Some parts of the brain do seem to be especially concerned with such things as analysis of visual input, control of muscular movements, language understanding and production, awareness of the spatial layout of your surroundings, etc., but even those parts almost certainly do other things too, and other (or even most) parts of the brain are almost certainly involved to some degree in all these functions as well.

That pretty much sums it up. We don’t know as much as we think we do, and we don’t think we know much.

The theory of lobotomy was to remove impulse and uncontrolled behaviour, but (biased) descriptions generally suggest it turns people into docile zombies - really an exaggeration, but if creativity is close to madness, it’s possible. Creativity can probably be described as impulsive activity.

Basically the brain is a complex, interlocking mechanism and messing with one piece can have lots of unintended consequences. A significant outcome of some lobotomies was epileptic convulsions - definitely a sign the brain is seriously messed up.

Another interesting stat I heard once- the brain consumes up to 1/3 of the nutrition we need. Therefore, unless it gives us a significant advantage for survival it is a waste of calorie. Since there are 7 billion of us, obviously it does the job; but that is why a horse or dog or rabbit only gets as much brain as they need to do their job. Excess brain is a waste of calories if all you need to do is, for example, run faster…

Psychological neuroanatomy is indeed a very grey area. (see what I did there?) However, much work has been done to attain a fairy advanced understanding of the regulation of homeostasis, movement, and sensation. Here are a few starter locations:

Motor control:
Primary Motor Cortex - This is located in the precentral gyrus. If I instructed you to raise your left arm, your right prefrontal gyrus would light up on an fMRI. It is responsible for gross motor control and lesions here cause paresis and paralysis.
Supplementary Motor Area - This is located just in front of the Primary Motor Cortex, and together with the cerebellum, is responsible for “muscle memory.” While the PMC is responsible for “raise your arms in the air”, the Supplementary Motor Area is responsible for “make a basketball shot.”
Cerebellum - This region of the brain plays a similar role as the SMA, but lesions here cause distinctly different symptoms. The cerebellum is responsible for coordinating all of your movements so that they flow smoothly and work together. The reason why uncoordination is one of the first signs of being drunk is because the cerebellum is one of the first structures affected by alcohol. (big) Lesions here make people look like they are very, very drunk.

All of these systems communicate between themselves via highly conserved tracts, nuclei, and nerves. In fact, almost all of the motor fibers can be found within the lateral corticospinal, anterior corticospinal, rubrospinal, vestibulospinal, corticobulbar, and tectospinal tracts.

In addition, there are also relay nuclei which are critical for normal neurological function. There are a ton of them, but basically each cranial nerve has at least one (some are shared, other cranial nerves have multiples like the trigeminal) Knocking out these nuclei will cause specific deficits. For instance, a paramedian lesion of the caudal pons will often involve the abducens nucleus, making it so that you can’t look to one side with either eye.

It sounds bad, but its not really. Just alot of memorization.

Just as an example of how complicated the whole matter is, see Vinken Bruyn’s so-called “Handbook of Clinical Neurology”, which runs to some 75+ volumes. Google page.

Warning: it takes some time to load. At page 40 you will see a bunch of entries dealing with the frontal lobe, frontal lobe lesions, and frontal lobe syndrome.

If you look for the other areas noted by heavyarms I’m sure you’ll find many more entries.

Yeah, about 15 kcal/hr, so maybe 300 or 400 kcal per day. Probably less than a third, but way disproportionate for its weight. (Average brain weighs about 1.4 kg; average person weighs, say, 70 kg; so 2% of your weight uses around 20% of your calories)

Here’s a cite for anyone who wants to know more (look almost half-way done for the section entitled “Regulation of Cerebral Metabolic Rate”.)

The April 2010 issue of Scientific American has an article about neuroscience revealing the malfunctioning connections underlying psychological disorders, necessitating the rethinking of mental illness. Neural imaging is revealing that abnormal activity along a circuit of brain structures involved in mental processing underlies many mental disorders. A partial list of the brain structures involved in mental disorders includes, along with the prefrontal cortex, the hypothalamus, “Area 25,” amygdala, hippocampus, insula, caudate nucleus, orbitoforntal cortex, Huntington’s circuit, motor cortex, basal ganglia, and thalamus. In addition, the pfc is divided into the dosolateal pfc and ventromedial pfc.

Check out Phantoms in the Brainby Ramachandran (Amazon link). It discusses, in pretty digestible layman’s speak, both how various parts of the brain function, but just as importantly, the fundamental plasiticity of the brain - citing examples where brains are damaged and other, functioning parts, compensate for the damaged part. Or a part of the body that the brain controls, etc. an arm, is damaged, so the part of the brain devoted to that limb ends up focusing on some other body part/sense…

Brain and brain, what is brain?

Parts of the brain.

I love this video of a young girl that needed to have half of her brain removed due to seizures, “Magellan’s Syndrome”. She functions fine after with only slight paralysis in the right arm because of Plasticity. The Brain is amazing!

Plasticity

–He works closely with Pinky.

What?

Long the standard authoritative explanation of the brain, this is the short film shown to all med students.