Lateralization of the Brain: Hemispheric Specialization

Contralateral movement: Right side of the brain controls muscles on the left side of body. Left side of the brain controls muscles on the right side of body. Contralateral sensation: Sensory information from the left side of the body crosses over to the right side of the brain Sensory information from the right side of the body crosses over to the left side of the brain.

Left hemisphere dominant functions: Language & speech Controls logic, reasoning, & (math) analytical thought processes (math) Recognizes sequences of words and letters Can focus on details, but has difficulty comprehending the whole picture Right hand/right side of body movement Right side of body sensations Right hemisphere dominant functions: Analysis of space & geometrical shapes & forms/patterns Creativity Comprehension of emotion/facial expressions Can "see" the whole out of parts (connect puzzle parts). Facial recognition Intonation Left hand/left side of body movement Left side of body sensations

Left brain dominates for language, speech, logic and problem-solving Right brain dominates for spatial, creative, visual-motor tasks

corpus callosum connects brain’s 2 hemispheres

Splitting the Brain A procedure in which the two hemispheres of the brain are isolated by cutting the connecting fibers (mainly those of the corpus callosum) between them. Corpus Callosum Martin M. Rother Courtesy of Terence Williams, University of Iowa

Human split brain operations - treatment for severe epilepsy -results: - decrease in seizures - same personality, motor functions - perception & memory not normal (like cats) A NOTE ABOUT VISION: everything in the left side of a scene goes to the right brain all in the right side of a scene goes to the left side. FOR BOTH EYES

SPLIT BRAIN EXPERIMENTS Roger Sperry & Ronald Myers - - severed the corpus callosum of cats - trained to do tasks with one eye blindfolded - switched blindfold to other eye & cat could not perform task (like it never learned it) - had to be taught the task again - one side of the brain didn’t know what the other had done! - further experimentation on monkeys first human split brain operation

The Divided Brain pid=1573

point Patient is asked to point to a whole, normal picture of the face that was just seen woman's Usually picks out the woman's picture (the information about the woman's face went to the RIGHT cerebral hemisphere). chimeric figure Patient focuses on the dot in the middle of the forehead woman's face Visual information about the woman's face goes to the right cerebral hemisphere man's face Information about the man's face goes to the left hemisphere left hemisphere. ONE SPLIT BRAIN EXPERIMENT SAYman Patient is required to SAY whether the picture was a man or a woman, the patient will say it was a man. Depending on what the patient is required to do, either the right or left hemisphere will dominate. In this case, when speech is not required, the right hemisphere will dominate for recognition of faces.

Another type of split-brain study Subject fixates on a center dot Sees a picture or a word on the right or left side of the dot. May be asked to respond verbally, by reading the word or naming the picture. May also be asked to respond without words, for example, by picking out a named object from among a group spread out on a table and hidden from view, so that it can only be identified by touch.

Split Brain Patients With the corpus callosum severed, objects (apple) presented in the right visual field can be named. Objects (pencil) in the left visual field cannot.

Split-brain patient looks straight ahead, focusing on a dot in the middle of screen right Picture of a spoon is flashed to the right of the dot (not pictured). Visual information about the spoon crosses in the optic chiasm & ends up in the ______________________ HEMISPHERE. When the person is asked what the picture was, the person will ____________________________________________________________ YET ANOTHER EXPERIMENT BUT YOU EXPLAIN WHAT HAPPENS! left If the spoon had been flashed to the left of the dot (see the picture), then the visual information would have traveled to the _________________ HEMISPHERE. If the person is asked what the picture was, the person will say __________________________. LEFT When this same person is asked to pick out an object using only the LEFT hand, this person will _____________________________________. This is because touch information from the left hand crosses over to the ____________ hemisphere - the side that "saw" the spoon. If the person is again asked what the object is, when it is there in the person's hand, will the person be able to say what it is? Why or why not???

Split-brain patient looks straight ahead, focusing on a dot in the middle of screen right Picture of a spoon is flashed to the right of the dot. Visual information about the spoon crosses in the optic chiasm and LEFTHEMISPHERE ends up in the LEFT. HEMISPHERE When the person is asked what the picture was, the person has no problem identifying the spoon and says "Spoon." If the spoon had been flashed to the left of the dot (see the picture), then the visual information RIGHTHEMISPHERE would have traveled to the RIGHT HEMISPHERE. that nothing was seen If the person is asked what the picture was, the person will say that nothing was seen!! But, when this same person is asked to pick out an object using only the LEFT hand, this person correctly pick out the spoon will correctly pick out the spoon. This is because touch information from the left hand crosses right over to the right hemisphere - the side that "saw" the spoon. the If the person is again asked what the object is, even when it is there in the person's hand, the person will NOT be able to say what it is because the right hemisphere cannot "talk." HOW DID YOU DO??

clawleftsnow Each hemisphere was presented a picture (chicken claw to left hemisphere; snow scene right to right hemisphere. point to the image that related Had to point to the image that related to what they saw from four pictures presented. The left and right hemispheres easily picked the right card. left handshovel The left hand pointed to the right hemisphere's choice (shovel) right handchicken The right hand pointed to the left hemisphere's choice (chicken). whyshovel Was asked why the left hand was pointing to the shovel. PROBLEM PROBLEM: Only the left hemisphere can talk, and it did not know the answer because the decision to point to the shovel was made in the right hemisphere. FURTHER RESEARCH MICHAEL GAZZANIGA - showed that the left hemisphere attempts to compensate for it's lack of information & the right hemisphere attempts to get it's knowledge conveyed. HOW? left hemisphere Immediately the left hemisphere made up a story about what it could see --- the chicken. chose the shovel to clean out a chicken shed It said the right hemisphere chose the shovel to clean out a chicken shed. WHAT HAPPENED??

Try This! Try drawing one shape with your left hand and one with your right hand, simultaneously. BBC

/20306/ Dc&feature=player_embedded Scientific American Frontiers Severed corpus callosum

The brain is sculpted by our genes but also by our experiences. Plasticity refers to the brain’s ability to modify itself after some types of injury or illness. The Brain’s Plasticity

Brain Plasticity & Hemispherectomies What is a hemispherectomy? – Surgically removing one hemisphere from a person’s brain Why? How does it affect person’s function? What is meant by brain plasticity? How does plasticity affect recovery from a hemispherectomy?

/20470/ Plasticity Brandi’s story: Dkoc&feature=relatedhttp:// m/watch?v=pVTWDuwDkoc&feature=related Kaci’s story: Q&feature=related