Brain Lateralization

One Brain or Two?

Gazzaniga, M. S. (1967)

Scientific American Frontiers: Right/left brain

Corpus Callosum

Split Brain SurgeryA procedure in which the two

hemispheres of the brain are isolated by

cutting the connecting fibers

(mainly those of the corpus callosum) between them.

With the corpus callosum severed,

objects (apple) presented in the

right visual field can be named. Objects (pencil) in the left visual field cannot.

• Left hemisphere – language, logic, laughter– Controls the right side of the

body– Logical, verbal, sequential– Positive emotions

• Right hemisphere – – Control the left side of the body– Spatial, emotional intuition,

music, “big picture”(Neat fact: People with damage to

the left hemisphere may lose their ability to speak but not sing (a right hemisphere task). They can redevelop language by learning to sing everything they want to say!)

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1. What is the large composite letter?

H (right brain active)

2. What is the small component letter?

D (left brain active)

Which face looks happier to you?

http://www.youtube.com/watch?v=roKV8XJHXKc&feature=related

http://nobelprize.org/educational/medicine/split-brain/splitbrainexp.html

FORK SPOON

• When asked to SAY what they saw, they answer __________________– (spoon)

• When asked to pick up what they saw with their left hand, they will pick up a ______.– (fork)

Dr. J briefly flashed a picture of a key in the right visual field of a split-brain patient. The patient could probably

A. verbally report that a key was seen

B. write the word “key” using her left hand

C. draw a picture of a key using the left hand

D. none of the above

Answer: A

A split brain patient has a picture of a knife flashed to her left hemisphere and that of a fork to her right hemisphere. She will be able to

A. identify the fork using her left hand.

B. identify the knife using her left hand.

C. identify the knife using either hand.

D. identify the fork using either hand.

Answer: A

What will happen as a neurosurgeon sedates the entire right cerebral hemisphere of a patient who is asked to count aloud with both arms extended upward?

A. her left arm will fall and she will become speechless

B. her right arm will fall and she will become speechless

C. her left arm will fall and she will continue counting

D. her right arm will fall and she will continue countingAnswer: c

• People should typically recognize familiar words more rapidly when spoken into their __________ ear.Answer: right

• People should typically recognize familiar melodies more rapidly when played into their ________ ear.Answer: left

Note: Not all people have such simple separations between hemispheres. Women (more than men) tend to use both sides of their brain when interpreting language.

Plasticity – the brain’s capacity to reorganize

• Blind person’s sensory cortex for their fingers may expand.

• In blind people, the visual cortex is activated when they read Braille.

• In deaf people, some visual information is process in the temporal lobe.

• Hemispherectomy – removal of an entire hemisphere of cerebral cortex; if surgery performed when young, other hemisphere takes over