Splenium tumours

[jsmith613]

Crossman and Neary write that...
"Destruction of the splenium of the corpus callosum by stroke or tumour leads to the posterior disconnection syndrome of alexia without agraphia. Such individuals speak and write without difficulty but cannot understand written material (alexia). Disconnection of visual processing in the right hemisphere from the verbal processing of the dominant left hemisphere is thought to explain the syndrome"

I thought that visual processing was not dominant to one hemisphere and that if it was it was dominant to the left hemisphere anyway because more people have stronger left eyes. I am aware that language processing occurs mainly in the left hemisphere...but nonetheless I am confused.

Why then do people who suffer from splenium tumours find reading difficult? thanks

[fiveworlds]

The corpus callosum is a very large fibre tract connecting the cerebral hemispheres which allows communication between the cerebral hemispheres. Vision and Reading is located in the occipital lobe at the back of your head the frontal lobe allows for language comprehension. Any damage to this tract may interrupt the ability of these two areas to properly communicate with one another.

 

Such individuals speak and write without difficulty but cannot understand written material (alexia).

 

Speech and writing are in the frontal lobe. Usually in one hemisphere. In some people it may be in both hemisphere and then there will be some damage to speech comprehension but this largely depends on the person. They may also have damage to their motor skills if that is also in both hemispheres

 

Edited January 10, 2015 by fiveworlds

[iNow]

Reading is about much more than just seeing letters. Those visual images need to get translated by other parts of the brain to allow for interpretation of language and comprehension.

[fiveworlds]

Reading is about much more than just seeing letters. Those visual images need to get translated by other parts of the brain to allow for interpretation of language and comprehension.

 

exactly you interpret what you see in the occipital lobe (vision) but to interpret what you see as a language you use the frontal lobe and the corpus callosum connects the two. The damage may not be perfect as in dyslexia where some of the words will appear jumbled etc and you may be able to speak fine and spell words out perfectly but reading them can be difficult

Edited January 10, 2015 by fiveworlds

[iNow]

exactly you interpret what you see in the occipital lobe (vision) but to interpret what you see as a language you use the frontal lobe and the corpus callosum connects the two.

The corpus collossum connects the left and right hemispheres, not the front and back (at least not in the ways you seem to be suggesting). You are correct, though, that it plays an important role in transferring signals to all of the various parts of the brain involved in reading.

 

The left brain right brain and language sections of the following site are accessible and informative:

 

http://www.mayfieldclinic.com/PE-AnatBrain.htm#.VLGvp7qCOK0

Edited January 10, 2015 by iNow

[fiveworlds]

The corpus collossum connects the left and right hemispheres, not the front and back (at least not in the ways you seem to be suggesting).

 

Okay lets say my language area is in my left hemisphere and the vision area is in the right back hemisphere. They aren't always there it varys from person to person. Some people have their motor function(ability to write) in both hemispheres(ambidextrous) some are left/right handed. It is why some people get dyslexia but not dyspraxia sometimes one area or both areas are divided between the two hemispheres. Or they could be dyspraxic but not dyslexic/dyspraxic and dyslexic(less common). Other reasons could be exactly where the damage to the corpus collosum actually was just because somebody is only dyslexic does not mean that both areas are not shared between two hemispheres. Now to figure out where these areas are on you the neurosurgeon will most likely run an EEG(Electroencephalogram)/FMRI on you which will show them areas which light up on their monitor when you speak etc

Edited January 10, 2015 by fiveworlds

[iNow]

Why then do people who suffer from splenium tumours find reading difficult? thanks

Because it interrupts the neural signal from reaching in a coordinated way all of the various parts of the brain required to read successfully.

 

Okay lets say my language area is in my left hemisphere

It's more accurate to refer to the Brocha's area and Wenicke's area.

 

and the vision area is in the right back hemisphere.

There is no "back hemisphere." Vision is processed in the occipital lobe via the optic nerve, as you rightly shared above. Reading is different from seeing, though.

 

Some people have their motor function(ability to write) in both hemispheres(ambidextrous) some are left/right handed.

Most people have their motor function in both hemispheres. The ability to write involves much more than just the ability to move ones hands, though.

[fiveworlds]

It's more accurate to refer to the Brocha's area and Wenicke's area.

 

Is it necessary to go into that much detail? It isn't a problem I can name every area pretty much

Vision is processed in the occipital lobe

 

The corpus callosum is a very large fibre tract connecting the cerebral hemispheres which allows communication between the cerebral hemispheres. Vision and Reading is located in the occipital lobe at the back of your head the frontal lobe allows for language comprehension

There is no "back hemisphere."

 

I believe I said the right back hemisphere as in the back of the right hemisphere

Ps for the example given it would be the Brocha's area and not the Wenicke's area. The Brocha's area is located in the frontal lobe.

Edited January 11, 2015 by fiveworlds

[iNow]

The corpus callosum is a very large fibre tract connecting the cerebral hemispheres which allows communication between the cerebral hemispheres.

Correct.

 

Vision and Reading is located in the occipital lobe at the back of your head the frontal lobe allows for language comprehension

As shared already above, while we see and perceive visual information like text characters in the occipital, it is not accurate to claim that this is where "reading" takes place.

 

I am glad to see you have such an interest in the brain. You also seem to know more than many people. It's important for you to be much more cautious when answering questions, though. Precision of language is critical when your goal is the accurate teaching of others such as the OP.

[fiveworlds]

As shared already above, while we see and perceive visual information like text characters in the occipital, it is not accurate to claim that this is where "reading" takes place.

 

 

The Wernicke's area deals with hearing not reading. That's why it has to be in the frontal lobe.

 

You also seem to know more than many people

 

I wish there is so much to memorize

Edited January 11, 2015 by fiveworlds

[jsmith613]

 

The Wernicke's area deals with hearing not reading. That's why it has to be in the frontal lobe.

 

I wish there is so much to memorize

 

 

Correct.

 

As shared already above, while we see and perceive visual information like text characters in the occipital, it is not accurate to claim that this is where "reading" takes place.

 

I am glad to see you have such an interest in the brain. You also seem to know more than many people. It's important for you to be much more cautious when answering questions, though. Precision of language is critical when your goal is the accurate teaching of others such as the OP.

 

Thank you to both of you for your help.

I think I get the idea but my confusion lies in the concept of a dominant visual processing lobe hemisphere? I didn't think such a thing existed (as we are binocular)...hence even if information cannot pass from right to left surely visual information reaching the left hemisphere could be intepreted? thanks

[iNow]

Recall that there is not a dominant HEMISPHERE for processing visual information, but instead a dominant LOBE, and it's located at the back of our heads. The optic nerve that carries information from our eyes to our brains is also quite cool in that it sends visual information from EACH eye to EACH hemisphere.

 

We are really oversimplifying this here, and there is a lot going on underneath these broad descriptions being offered.

 

Here's a helpful animation about the processing of visual information. The parts about the brain start a few minutes in, but the whole 6 minutes is wor the watch:

 

http://www.sumanasinc.com/webcontent/animations/content/visualpathways.html

[fiveworlds]

There is actually a second area involved in reading and writing there is the Broca's area but there is also an unlabeled(not named area just labeled reading) located directly underneath the wernicke's area in the occipital lobe.

[jsmith613]

Recall that there is not a dominant HEMISPHERE for processing visual information, but instead a dominant LOBE

 

Yes. So the occipital lobe is involved in processing visual information. And as I understand this occurs equally well on both sides.

I'm not sure if I am being unclear with my question or if I am just not understanding what your saying but if the occipital lobe processes visual information (equally well on both sides) then who cares if the one of the occipital lobes is damaged?

Do we really need both lobes? I thought the right lobe delt with information in the left and the left lobe delt with information on the right

 

So if the reading material was presented to the left occipital LOBE then surely it could transfer to the language centres so it can be processed for intepretation by the brain and comprehension?

 

have I missed something you were saying?

 

thanks again for sticking with me through this problem

[iNow]

There is only one occipital lobe. It is one of four primary, and this is a separate idea from the idea of he spheres (which literally means "half of a sphere"). The other lobes (like the frontal and parietal and temporal) are dominant for other traits like reasoning and math, motor skills and ability to move, etc. then there is the stuff below them in the core of the brain that relate to emotion and memory and management of systems like the heart and breathing.

 

As far as I know, the occipital lobe is the least bilaterally differentiated of any of them. Back to your original question, I suspect the reading disruption at the corpus collassum level plays out later in the interpretation process, after the signal has already left the occipital. This is just speculation from me, though. I'm rusty in this space.

[jsmith613]

There is only one occipital lobe. It is one of four primary, and this is a separate idea from the idea of he spheres (which literally means "half of a sphere"). The other lobes (like the frontal and parietal and temporal) are dominant for other traits like reasoning and math, motor skills and ability to move, etc. then there is the stuff below them in the core of the brain that relate to emotion and memory and management of systems like the heart and breathing.

 

As far as I know, the occipital lobe is the least bilaterally differentiated of any of them. Back to your original question, I suspect the reading disruption at the corpus collassum level plays out later in the interpretation process, after the signal has already left the occipital. This is just speculation from me, though. I'm rusty in this space.

Ok...it seems i've misunderstood something more fundemental. I thought we had 2 of each lobe (2 parietal, 2 frontal...) and each of these lobes were connected my commisural fibres. Is this false? Is there only 1 of each lobe? If so why is it that we have a divide in middle of our brains (middle long. fissure)?

[iNow]

It's just an issue of language. No fundamental misunderstandings that I can see. Just terminology. We have one of each lobe, but each lobe has to sides. Likewise, we have one face with two sides and one torso with two sides and one butt with two sides... Same across the brain and its lobes...One of each lobe, each with two sides.

 

The bilateral split in our bodies goes all the way down from head to toe and has many biological, evolutionary, and developmental reasons for existing (in sum, that's a much broader question).

 

http://www.sciencedaily.com/releases/2009/09/090923112543.htm

[jsmith613]

It's just an issue of language. No fundamental misunderstandings that I can see. Just terminology. We have one of each lobe, but each lobe has to sides. Likewise, we have one face with two sides and one torso with two sides and one butt with two sides... Same across the brain and its lobes...One of each lobe, each with two sides.

 

The bilateral split in our bodies goes all the way down from head to toe and has many biological, evolutionary, and developmental reasons for existing (in sum, that's a much broader question).

 

http://www.sciencedaily.com/releases/2009/09/090923112543.htm

 

There is actually a second area involved in reading and writing there is the Broca's area but there is also an unlabeled(not named area just labeled reading) located directly underneath the wernicke's area in the occipital lobe.

 

Ok...I think I get it now. thank you both for your help I really appreciate it!