On what basis are parts of the brain classified?

[Frigus]

On the basis of what brain is classified,like we say on the basis of function the neurons are of 3 types.

 

[jim mcnamara]

Hmm. I'm having trouble getting your meaning. We are classifying "brain types". Correct? Can you give us an example possible answer?

 

[Frigus]

Hmm. I'm having trouble getting your meaning. We are classifying "brain types". Correct? Can you give us an example possible answer?

Sorry,I was talking about classification of brain parts which are classified into 3 types fore brain,mid brain,hind brain

 

[jim mcnamara]

In humans, those are called the cerebrum, cerebellum, and the medulla oblongata - respectively
A superficial explanation:
Cerebrum - complex thought, memory, associations, language, image processing
Cerebellum - movement, preprocessing neural input like touch and hearing
Medulla oblongata - autonomic nervous system control - breathing, heart rate.

Does that help?

 

[Frigus]

In humans, those are called the cerebrum, cerebellum, and the medulla oblongata - respectively
A superficial explanation:
Cerebrum - complex thought, memory, associations, language, image processing
Cerebellum - movement, preprocessing neural input like touch and hearing
Medulla oblongata - autonomic nervous system control - breathing, heart rate.

Does that help?

Thanks a lot,it makes sense because we know that these some of the parts work together to achieve the function written above so then we can classify the parts which toghether achieve a particular function but the problem is that what was need to say them fore brain,mid brain,hind brain.

 

[jim mcnamara]

If I understand - the answer is that biology has always been filled with terms that were redundant, or are used by non-technical people versus terms used by professionals
Example using camels:
"one hump camel" == dromedary == Camelus dromedarius == Arabian camel
"two hump camel" == bactrian == Camelus bactrianus == Mongolian camel

These terms are okay, depending on who you are speaking with.

 

[BillTre]

3 types fore brain,mid brain,hind brain

With respect to vertebrate brains, the (what I would call) sections or regions of the brain are ubiquitous (found in all vertebrate brains). They arise during the embryology of the CNS (central nervous system). The hindbrain (which I did my thesis on) is continuous with the spinal cord and and gradually blends into it as one moves from the head to the body. The only reason the spinal cord is not considered a part of the brain is that it is not in the head, but contained in the spinal column.

As @jim mcnamara said, they also have other names forebrain: prosencephalon, midbrain: mesencephalon, hindbrain: rhombencephalon. As development proceeds, these regions develop further subdivisions with more additional weird names. Here is a Wikipedia article on this. I could (literally) write a thesis on this, but there are a lot of on-line sources, including other Wikipedia articles that can be searched out.
For example, the cerebellum sits on top of the hindbrain and appears to be evolutionarially derived from the either otic (hearing) or balance nuclei (concentrations of neurons subserving a function) or from adjacent areas in the dorsal hindbrain. As evolution proceeded and brains developed more refined regions, the changes in the adult structures were made by small changes in the developmental program the generates a species's brain structures.
Its indirect, in small steps, and repeated millions of times.

The vertebrate CNS was most likely evolved from something like the amphioxus CNS, which lacks a distinct brain and whose head is also not very developed.
A series of animals with differing amounts of brain organization leading upto vertebrates (but not the actual evolutionary sequence) would be: amphioxus, hagfish/lampreys (a disputed demarcation line between ventebrates and non-vertebrates is around here), then the fish (a large and very diverse group, some of which evolved into tetrapods (vertebrates with four limbs). A group that includes more than the "vertebrates" is the "craniates". Amphioxus, however, is not a member of either group.
Embryonically fish CNS has all the parts of the human.
Different parts just develop to different extents to make the vertebrate brains of different species.

Other species have brains too, like insects. They are independently evolved and also have distinct brain regions which have different names.

 

[atyy]

Sorry,I was talking about classification of brain parts which are classified into 3 types fore brain,mid brain,hind brain

The neural tube, which develops into the brain and spinal cord, develops 3 swellings or bulges. These 3 bulges from front to back correspond to forebrain, midbrain and hindbrain.

Figure 2 of the following link shows a schematic of these swellings.
https://opentextbc.ca/anatomyandphysiology/chapter/13-1-the-embryologic-perspective/

 

[Frigus]

The neural tube, which develops into the brain and spinal cord, develops 3 swellings or bulges. These 3 bulges from front to back correspond to forebrain, midbrain and hindbrain.

Figure 2 of the following link shows a schematic of these swellings.
https://opentextbc.ca/anatomyandphysiology/chapter/13-1-the-embryologic-perspective/

Thanks,this article was quite easy to read and also due it i understand how we classified the brain regions.

 

[DiracPool]

For the most part, these distinctions/classifications are arbitrary. Most of the descriptions in the posts above are archaic labeling of gross anatomical structures viewed in dissection in the 19th and early 20th centuries of similarly archaic tissue slides. For example, the substantia nigra, or "black substance" in Greek, in the brainstem that houses the brain's NE neurons was so-called because that small nucleus of roughly 10K cells stained black under gross microscopic observation. Same thing with the red nucleus--another brain-stem structure that appears red under magnification. Then we have the "striate" cortex, or the V1 visual area/area 17 of the occipital lobe. This is so named because early anatomists viewed striations, or stripes in the V1 regions that demarked ocular dominance columns.

So, take the standard hierarchical subdivision nomenclature of the brain with a grain of salt. Use it as a first approximation, but be ready to eventually to define your own classification after steady research.

 

[atyy]

For example, the substantia nigra, or "black substance" in Greek, in the brainstem that houses the brain's NE neurons was so-called because that small nucleus of roughly 10K cells stained black under gross microscopic observation.

The substantia nigra or "black substance" houses dopamine neurons, not NE (norepinephrine) neurons.
Many NE neurons are in the locus coeruleus - where "coeruleus" indicates "blue".
https://en.wikipedia.org/wiki/Substantia_nigra
https://en.wikipedia.org/wiki/Locus_coeruleus

Then we have the "striate" cortex, or the V1 visual area/area 17 of the occipital lobe. This is so named because early anatomists viewed striations, or stripes in the V1 regions that demarked ocular dominance columns.

There are ocular dominance columns in striate cortex or primary visual cortex, but primary visual cortex was called striate cortex for because the appearance caused by white matter running through it: https://en.wikipedia.org/wiki/Line_of_Gennari

 

[BillTre]

For the most part, these distinctions/classifications are arbitrary. Most of the descriptions in the posts above are archaic labeling of gross anatomical structures viewed in dissection in the 19th and early 20th centuries of similarly archaic tissue slides.

The distinctions (and terminology) based on embryonic structures may seem irrelevant to those only interested in structures or physiological functioning of the adult brain.
However, some of these names have significance based upon based their being early embryonic structures.
Brain development builds upon these early structures which lay down the framework within which later developmental events happen. Your brain (or the brain of any vertebrate) would not be the same without them.
Mutations affecting embryonic development show that when early developing regions are lacking or messed-up, the the later arising structures that would be in those regions are also lacking or messed-up in their organization.

 

[sysprog]

The substantia nigra or "black substance" houses dopamine neurons, not NE (norepinephrine) neurons.

The substantia nigra, which is largely destroyed by toxic levels of nitric oxide in Parkinson's Syndrome, although it has strongly dopaminergic function, also has norepinephrinergic, acetlycholinergic, and serotoninergic functions.

Many NE neurons are in the locus coeruleus

I think that you're right about NE being largely from the locus coeruleus.

But it's very complicated . . .

 

[DiracPool]

@atyy

Thank you for correcting my careless oversights in relation to to the correct classification of the monoaminergic nuclei nomenclature ("substantia nigra") and real origin of the striations in the primary visual cortex. My vodka consumption has spiked recently with the shelter at home orders.

So, let's get back to the OP's main question (as we should). Basically, the OP was interested in the origin of how brain regions and their functions are classified. I'll revert again to say that this classification is largely the result of early anatomists simply looking at gross brain anatomy or brain sections under slices in the microscope and giving them Greek or Latin or Italian, etc. names. For example, everybody knows that the outer surface of the brain is called the "cortex." Why? Because that is the Latin name for "bark," as in the outer rind of a tree. As far as the the cerebral part of "cerebral cortex," the word "cerebrum" translates to "head wax" in Latin, so named for the waxy consistency of the substance on the tips of the swords of Roman soldiers who penetrated the heads of the enemy in battle.

Geographical partitions of the central nervous system, i.e., hindbrain, midbrain, prosencephalon, etc., were all just crudely assigned based on gross physical observation. Later on, in the 1950's +, there was physiological corroboration of these anatomical observations, but the groundwork of the nomenclature was well established far prior to this.

Case in point, the Brodmann maps. This is a map of the demarcations of the structural/functional geography of the human neocortex. Brodmann delineated these regions based, again, on a crude visual inspection of the cell types in each region, which were distinct for each delineated region. His claim of fame was making a map of those regions and then numbering them (see below).

@BillTre

So there is a phylogentetic component to this story as well. We know that, in the evolution of the brain, new regions built upon the previous architecture. Some of my personal research views the participation of fibrobrast growth factor 8 (FGF8) in this process. To put it simply, each progressive step or leap in the evolution of the primate/human brain was a process whereby a jolt in the production of a substance "like" FGF8 facilitated the anatomical development of a new brain region or enhancement of an existing region. As a new region, the neurons that would populate that region would necessarily have an architecture distinct from the phylogenetically older juxtaposed tissue. Hence, the evolution the Brodmann map.

 

[sysprog]

My vodka consumption has spiked recently with the shelter at home orders.

Please be careful -- take a glance at the clock whenever you take a drink, so that you can track how fast you're drinking . . .

As far as the the cerebral part of "cerebral cortex," the word "cerebrum" translates to "head wax" in Latin,

I think that maybe you're confusing or conflating 2 different etymologies -- in the mid 1700s the medical Latin term 'cerumen', used for earwax, was coined from Latin 'cera' which translates to 'wax'; however, 'cerebrum' is a (contemporaneous to that time but somewhat older) word meaning 'brain', derived from Proto-Indo-European keres (rooted in ker, meaning horn, tip or head).

 

[atyy]

The substantia nigra, which is largely destroyed by toxic levels of nitric oxide in Parkinson's Syndrome, although it has strongly dopaminergic function, also has norepinephrinergic, acetlycholinergic, and serotoninergic functions.

Can you give a reference for the statement about nitrix oxide? Is it securely established?

I think that you're right about NE being largely from the locus coeruleus.

Of the top of my head, I don't recall whether there is significance to noradrenergic (NE), cholinergic or serotonergic release by dopaminergic neurons of the substantia nigra. However, we do know the significance of dopamine co-release by the noradrenergic (NE) neurons of locus coeruleus.
https://pubmed.ncbi.nlm.nih.gov/27602521/
https://pubmed.ncbi.nlm.nih.gov/29123927/

 

[sysprog]

Can you give a reference for the statement about nitrix oxide? Is it securely established?

There are numerous articles firmly establishing this that have been published in peer-reviewed journals in the last 20 years -- here's one from 2015 such that the full-text version isn't paywalled: https://www.jneurosci.org/content/jneuro/35/8/3591.full.pdf

Of the top of my head, I don't recall whether there is significance to noradrenergic (NE), cholinergic or serotonergic release by dopaminergic neurons of the substantia nigra. However, we do know the significance of dopamine co-release by the noradrenergic (NE) neurons of locus coeruleus.
https://pubmed.ncbi.nlm.nih.gov/27602521/
https://pubmed.ncbi.nlm.nih.gov/29123927/

Well, the fact that a neuron can be dopaminergic should not lead us to conclude that it cannot also be norepinephrinergic (pretty much the same as noradrenergic, just as epinephrine is the same as adrenalin -- the adrenal glands are located outside (epi) the kidney (nephron)) -- neurons can be very adaptational.

 

[atyy]

There are numerous articles firmly establishing this that have been published in peer-reviewed journals in the last 20 years -- here's one from 2015 such that the full-text version isn't paywalled: https://www.jneurosci.org/content/jneuro/35/8/3591.full.pdf

That's in an MPTP model.

Well, the fact that a neuron can be dopaminergic should not lead us to conclude that it cannot also be norepinephrinergic (pretty much the same as noradrenergic, just as epinephrine is the same as adrenalin -- the adrenal glands are located outside (epi) the kidney (nephron)) -- neurons can be very adaptational.

Yes, but it is the locus coeruleus that is a better example of the point you wanted to make.

 

[sysprog]

That's in an MPTP model.

MPTP appears to be a possibly sufficient but not necessary precursor to toxic levels of nitric oxide damaging the substantia nigra. Toxic levels of nitric oxide are well established to be strongly correlated in a way that strongly suggests causality regarding the aforementioned destruction. You asked if I could provide a reference and I did. If you want more, please use a search engine.

Yes, but it is the locus coeruleus that is a better example of the point you wanted to make.

I don't disagree with the notion that the locus coeruleus is much more a source of norepinephrine than the substantia nigra is.

 

[atyy]

MPTP appears to be a possibly sufficient but not necessary precursor to toxic levels of nitric oxide damaging the substantia nigra. Toxic levels of nitric oxide are well established to be strongly correlated in a way that strongly suggests causality regarding the aforementioned destruction. You asked if I could provide a reference and I did. If you want more, please use a search engine.

What I mean is we don't know whether the MPTP model is a good model of the neurodegenerative process in Parkinson's. When applied in monkeys, it is great model of the result of the parts of the degenerative process that produce the major motor symptoms of Parkinson's. In other words, it may produce the same outcome, but by a different route.

 

[sysprog]

One thing that the different routes have in common is toxic levels of nitric oxide destroying neurons in the substantia nigra.

 

[BillTre]

As a new region, the neurons that would populate that region would necessarily have an architecture distinct from the phylogenetically older juxtaposed tissue. Hence, the evolution the Brodmann map.

I am thinking you are referring to the cytoarchitecture of the tissue within which the neurons reside.
When comparing the neurons from one cortical area with a neighboring area of cortex, the component neurons do not seem that distinct. One could argue that they are the same neurons utilized in different settings. Transcriptnomics may provide a more subjective answer.
The cytoarchitecture of the tissues of neighboring cortical areas are often related (sharing features of their structure location and function) and some areas can be experimentally transformed to assume functions of related areas.

Assuming your proposed scenario of new area formation is somewhat accurate (expression of some factor promotes expansion and formation of a new area), this can be interpreted as a subdivision followed of a pre-existing area, followed by an expansion of one (or more) of the new sub-parts.
From what I know of comparative neuroanatomy, many neighboring areas have neurons that share properties.
These things are not made anew (this would be too slow an approach for the observed rate of evolution to achieve), but are modifications of the previously existing structures, which are produced by the modifications of the developmental programs which generated the pre-existing older regions in the past (before the evolution of the new area(s).
This kind of relationship is much more likely based on a modification of that which is found in ancestors than a creation of an "new region" de novo.
Thus (at least in my mind), their embryonic origins remains an important part of their final adult state in each generation as evolution proceeds.

 

[sysprog]

@BillTre I think that you're right -- a single neuron can grow from head to toe (rarely, but not never (and that exceptional length includes dendritic projections)), and yes, neurons do have strong ability to imitate their neighbors.