Why memory and personality not affected after brain hemispherectomy

[rajeshmarndi]

Because when parts or one half of the brain(hemispherectomy) is removed on treating epileptic patients or for any other reason. There is not observed any change in the patient memory or personality.

The person remain the same even after removal of half of the brain. How is it explained?

Thanks.

 

[rajeshmarndi]

" [1] Studies have found no significant long-term effects on memory, personality, or humor,[4] and minimal changes in cognitive function overall."

http://en.wikipedia.org/wiki/Hemispherectomy

 

[zoobyshoe]

How is it explained?

It is the result of lateralization of brain function, obviously, and the apparent lack of deficit only happens when the non-dominant hemisphere is damaged.

You can get a deeper understanding by reading the short book, "My Stroke of Insight," by Jill Taylor. This is the autobiographical story of a neurologist who suffered a massive brain bleed that disabled her left hemisphere for something like eight years. That was her dominant hemisphere. During the time she was disabled she could just barely speak or understand speech anymore, and lived perceiving the world with only right hemisphere functions.

Her experience points out that what we think of as "personality" is a collection of (normally) left hemisphere functions that are inextricably linked to our language centers. The stories we tell ourselves and others about ourselves are left hemisphere constructs. The right hemisphere is not talkative and directly perceives things as they are without the constant commentary of the interior monolog.

So, when the dominant hemisphere is damaged, it's apparent the person is quite disabled, but when it's the non-dominant hemisphere the damage is hidden. When you talk to someone you're always talking to their left hemisphere, so to speak. If the left hemisphere is not damaged their personality will seem intact.

 

[Pythagorean]

" [1] Studies have found no significant long-term effects on memory, personality, or humor,[4] and minimal changes in cognitive function overall."

http://en.wikipedia.org/wiki/Hemispherectomy

Note that the context of this discussion is children! Children still have a lot of brain development ahead of them, which makes them great candidates for hemispherecetomy. Adults, on the other hand, suffer noticeable differences and the procedure is, therefore, not often performed on adults.

 

[rajeshmarndi]

Children still have a lot of brain development ahead of them, which makes them great candidates for hemispherecetomy.

Does the remaining portion of the brain, takes over all or most of the function from the removed hemisphere. Since child brain are more plasticity.

Such as language is in the left hemisphere, does the right hemisphere take the function and the child is able to speak. Also can the child later become free from paralysis to the opposite side of his body due to plasticity of child brain.

In other words, is it possible, with just only one hemisphere, can a child later does all the function what an normal person is capable.

 

[Pythagorean]

Yes.

And note, language isn't always in the left hemisphere. Left-handers have a greater chance (4-6 times the chance) than right-handers to have language in the right hemisphere. So about 5% for right-handers and from 15% to 27% in left-handers (depending on their degree of left-handedness).

http://brain.oxfordjournals.org/content/123/12/2512.abstract

 

[zoobyshoe]

In other words, is it possible, with just only one hemisphere, can a child later does all the function what an normal person is capable.

Yes.

You have a good link for this? What I doubt is that the unilateral paralysis is ever overcome.

 

[Pythagorean]

You have a good link for this? What I doubt is that the unilateral paralysis is ever overcome.

Although hemiparesis remained unchanged in the majority of our series, five demonstrated improvement. Improvement in hemiparesis in a few patients following hemispherectomy was reported in early studies (Krynauw, 1950; McKissock, 1953), one of which reported that of 17 patients, 12 remained unchanged, two were worse and three improved (McKissock, 1953). These outcome proportions resemble our own. In the six cases we report where hemiplegia worsened, one suffered temporary loss of ambulation which was regained after a week. Others have reported that all ambulant subjects who underwent hemispherectomy regained ambulation within 6 months (Duchowny et al., 1998) and that transient worsening of the hemiparesis occurred in some subjects following hemispherectomy with recovery to baseline function after several weeks (Wyllie et al., 1998). Most studies are concordant with our results which suggest that, in this population, the hemiparesis is likely to remain unchanged in the majority, with fewer showing an improvement or deterioration

http://brain.oxfordjournals.org/content/126/3/556.full

 

[zoobyshoe]

http://brain.oxfordjournals.org/content/126/3/556.full

I don't think "ambulation" necessarily means the ability to walk normally. I saw a girl on TV a few years back who had undergone one of these procedures for seizure control and she was "ambulatory" in the sense she walked by herself, but it was hardly normal. She shuffled slowly onstage pretty much dragging one leg and not swinging one arm, much like someone who'd had some small degree of recovery after a stroke. So, even though some small percentage become "ambulatory" I think it would be an exaggeration to say they can eventually become normal.

 

[rajeshmarndi]

Read some portion, My Stroke of Insight," by Jill Taylor.

Personality and languages (assuming language is in the left hemisphere) lies in the left hemisphere. So when left hemisphere is affected completely by a stroke. The person looses personality and hence the ability to reasoning and think. But he can experience things as they are, without judging them.

Does this makes every person who is affected like above, to feel and experience equally.

Since they lost their personality aspect. They see no difference between good and bad because the analyzing part or the chattering box is shut down. The state becomes like enlightened, nirvana, euphoria etc..

Can we call Mind as the chattering box and absence of this , is like free of mind, which makes one experience nirvana etc..

If personality is lost, does the person also looses memory? If it is not, he recognizes everyone and only experiences.

 

[Pythagorean]

I don't think "ambulation" necessarily means the ability to walk normally. I saw a girl on TV a few years back who had undergone one of these procedures for seizure control and she was "ambulatory" in the sense she walked by herself, but it was hardly normal. She shuffled slowly onstage pretty much dragging one leg and not swinging one arm, much like someone who'd had some small degree of recovery after a stroke. So, even though some small percentage become "ambulatory" I think it would be an exaggeration to say they can eventually become normal.

That's fair; my yes was more to do this question:

"Does the remaining portion of the brain, takes over all or most of the function from the removed hemisphere?"

In that many of the muscles on the opposite side can still be manipulated by the remaining hemisphere and, in some cases, show improvement in muscle control post-surgery. Generally, it's the upper arm and leg that they gain control over, but not the lower arm and leg. The same is observed in monkeys: monkeys who experienced the lesions while they were young showed a greater chance of (partial) recovery from hemiparesis than adults.

 

[zoobyshoe]

Read some portion, My Stroke of Insight," by Jill Taylor.

Personality and languages (assuming language is in the left hemisphere) lies in the left hemisphere. So when left hemisphere is affected completely by a stroke. The person looses personality and hence the ability to reasoning and think. But he can experience things as they are, without judging them.

Does this makes every person who is affected like above, to feel and experience equally.

Since they lost their personality aspect. They see no difference between good and bad because the analyzing part or the chattering box is shut down. The state becomes like enlightened, nirvana, euphoria etc..

Can we call Mind as the chattering box and absence of this , is like free of mind, which makes one experience nirvana etc..

If personality is lost, does the person also looses memory? If it is not, he recognizes everyone and only experiences.

In Jill Taylor's case, she didn't exactly lose her personality and she still felt strongly about some experiences being good while others were bad. On the other hand, she often felt a euphoric bliss, having been freed from the constant internal chatter, and being able to perceive things directly without constantly talking to herself about them in her head.

She didn't lose her memory except to the extent anyone's memory is tied up in words. She still knew her relatives were her relatives, for example, though she couldn't name the relationship, of course. All her visual and sensory memories of her life were intact. She learned to "think," that is, to work out problems, in a purely visual way, by manipulating visual memories.