Your SlideShare is downloading. ×
  • Like
Divided Brain PPt
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×

Now you can save presentations on your phone or tablet

Available for both IPhone and Android

Text the download link to your phone

Standard text messaging rates apply

Divided Brain PPt

  • 1,503 views
Published

 

  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
    Be the first to like this
No Downloads

Views

Total Views
1,503
On SlideShare
0
From Embeds
0
Number of Embeds
0

Actions

Shares
Downloads
34
Comments
0
Likes
0

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 1. Our dividedOur divided brainbrain  For more than a century, clinical evidence hasFor more than a century, clinical evidence has shown that the brain’s two sides serve differingshown that the brain’s two sides serve differing functions. Accidents, strokes, and tumors infunctions. Accidents, strokes, and tumors in the left hemisphere generally impair reading,the left hemisphere generally impair reading, writing, speaking, arithmetic reasoning, andwriting, speaking, arithmetic reasoning, and understanding. Similar lesions in the rightunderstanding. Similar lesions in the right hemisphere seldom have such dramatichemisphere seldom have such dramatic effects.effects.
  • 2.  Patients with speech problems gave early researchers thePatients with speech problems gave early researchers the first clues about how the brain is involved with language. Thefirst clues about how the brain is involved with language. The loss of the ability to speak is called "aphasia." The ancientloss of the ability to speak is called "aphasia." The ancient Greeks noticed that brain damage could cause aphasia.Greeks noticed that brain damage could cause aphasia. Centuries later, in 1836, Marc Dax described a group ofCenturies later, in 1836, Marc Dax described a group of patients who could not speak properly. Dax reported that allpatients who could not speak properly. Dax reported that all of these patients had damage to the left side of their brain. Aof these patients had damage to the left side of their brain. A quarter century later in 1861, Paul Broca described a patientquarter century later in 1861, Paul Broca described a patient who could say only one word..."tan." For this reason, Brocawho could say only one word..."tan." For this reason, Broca called this patient "Tan." When Tan died, Broca examinedcalled this patient "Tan." When Tan died, Broca examined his brain and found that there was damage to part of the lefthis brain and found that there was damage to part of the left frontal cortex. This part of the brain has come to be knownfrontal cortex. This part of the brain has come to be known as "Broca's Area."as "Broca's Area."
  • 3.  In 1876,In 1876, KarlKarl WernickeWernicke found that damage to a differentfound that damage to a different part of the brain also caused language problems. Thispart of the brain also caused language problems. This area of the brain ("Wernicke's Area"), was further backarea of the brain ("Wernicke's Area"), was further back and lower in the brain compared to Broca's area. In fact,and lower in the brain compared to Broca's area. In fact, Wernicke's area is in the posterior part of the temporalWernicke's area is in the posterior part of the temporal lobe. Broca's area and Wernicke's area are connectedlobe. Broca's area and Wernicke's area are connected by a bundle of nerve fibers called the arcuate fasciculus.by a bundle of nerve fibers called the arcuate fasciculus. Damage to the arcuate fasciculus causes a disorderDamage to the arcuate fasciculus causes a disorder called conduction aphasia. People with conductioncalled conduction aphasia. People with conduction aphasia can understand language, but their speech doesaphasia can understand language, but their speech does not make sense and they cannot repeat words.not make sense and they cannot repeat words.
  • 4. Speaking the WrittenSpeaking the Written WordWord  To speak a word that is read, information must first get toTo speak a word that is read, information must first get to the primary visual cortex. From the primary visual cortex,the primary visual cortex. From the primary visual cortex, information is transmitted to the posterior speech area,information is transmitted to the posterior speech area, including Wernicke's area. From Wernicke's area,including Wernicke's area. From Wernicke's area, information travels to Broca's area, then to the Primaryinformation travels to Broca's area, then to the Primary Motor Cortex.Motor Cortex.
  • 5. Speaking the HeardSpeaking the Heard WordWord  To speak a word that is heard, information must first getTo speak a word that is heard, information must first get to the primary auditory cortex. From the primary auditoryto the primary auditory cortex. From the primary auditory cortex, information is transmitted to the posterior speechcortex, information is transmitted to the posterior speech area, including Wernicke's area. From Wernicke's area,area, including Wernicke's area. From Wernicke's area, information travels to Broca's area, then to the Primaryinformation travels to Broca's area, then to the Primary Motor Cortex.Motor Cortex.
  • 6.  By 1960 the left hemisphere was well acceptedBy 1960 the left hemisphere was well accepted as the “dominant” or “major” hemisphere, and itsas the “dominant” or “major” hemisphere, and its silent companion to the right as thesilent companion to the right as the “subordinate” or “minor” hemisphere, and the“subordinate” or “minor” hemisphere, and the left, the one easiest to observe and study. Theleft, the one easiest to observe and study. The other side is there of course, but backstage. (forother side is there of course, but backstage. (for about 1 in 10 people, including one-fourth of allabout 1 in 10 people, including one-fourth of all left-handers, speech is processed in the rightleft-handers, speech is processed in the right hemisphere. But then researchers found thathemisphere. But then researchers found that the “minor” right hemisphere was not so limitedthe “minor” right hemisphere was not so limited after all. The story of this discovery is aafter all. The story of this discovery is a fascinating chapter in psychology’s history.fascinating chapter in psychology’s history.
  • 7.  In 1961, two Los Angeles neurosurgeons, PhilipIn 1961, two Los Angeles neurosurgeons, Philip Vogel and Joseph Bogen, speculated that majorVogel and Joseph Bogen, speculated that major epileptic seizures were caused by anepileptic seizures were caused by an amplification of abnormal brain activity thatamplification of abnormal brain activity that reverberated between the two hemispheres.reverberated between the two hemispheres. They therefore wondered whether they couldThey therefore wondered whether they could reduce seizures in their patients withreduce seizures in their patients with uncontrollable epilepsy by cuttinguncontrollable epilepsy by cutting communication between the hemispheres. Tocommunication between the hemispheres. To do this, Vogel and Bogen would have to severdo this, Vogel and Bogen would have to sever thethe corpus callosum,corpus callosum, the wide band of axonthe wide band of axon fibers connecting the two hemispheresfibers connecting the two hemispheres
  • 8.  In a normal brain, stimuli entering one hemisphere isIn a normal brain, stimuli entering one hemisphere is rapidly communicated by way of therapidly communicated by way of the corpuscorpus callosumcallosum toto the other hemisphere, so the brain functions as a unit.the other hemisphere, so the brain functions as a unit. When the corpus callosum of an individual is severed,When the corpus callosum of an individual is severed, leaving a split brain, the two hemispheres cannotleaving a split brain, the two hemispheres cannot communicate. In some forms ofcommunicate. In some forms of epilepsyepilepsy a seizure willa seizure will start in one hemisphere, triggering a massive discharge ofstart in one hemisphere, triggering a massive discharge of neurons through the corpus callosum and into the secondneurons through the corpus callosum and into the second hemisphere. In an effort to prevent such massive seizureshemisphere. In an effort to prevent such massive seizures in severe epileptics, neurosurgeons can surgically severin severe epileptics, neurosurgeons can surgically sever the corpus callosum, a procedure called athe corpus callosum, a procedure called a commissurotomy. If one side of the brain can no longercommissurotomy. If one side of the brain can no longer stimulate the other, the likelihood of severe epilepticstimulate the other, the likelihood of severe epileptic seizures is greatly reduced.seizures is greatly reduced.
  • 9.  In a cerebral commissurotomy the surgeon opensIn a cerebral commissurotomy the surgeon opens the skull, lays back the brain's coverings and, withthe skull, lays back the brain's coverings and, with a tool called a cerebral retractor, exposes thea tool called a cerebral retractor, exposes the corpus callosum between the two hemispheres.corpus callosum between the two hemispheres. The doctor snips through the corpus callosum,The doctor snips through the corpus callosum, severing communication between thesevering communication between the hemispheres and preventing the transfer ofhemispheres and preventing the transfer of seizures .seizures .  They had tried this experiment with cats thenThey had tried this experiment with cats then monkeys with no serious ill effects. So Vogel andmonkeys with no serious ill effects. So Vogel and Bogen operated. The result? The seizures wereBogen operated. The result? The seizures were all but eliminated and the patients with theseall but eliminated and the patients with these splitsplit brainsbrains were surprisingly normal, theirwere surprisingly normal, their personalities and intellect hardly affected. Wakingpersonalities and intellect hardly affected. Waking from the surgery, one patient even managed tofrom the surgery, one patient even managed to quip that he had a “splitting headache”quip that he had a “splitting headache”
  • 10. The Corpus callosumThe Corpus callosum 
  • 11.  In general, the right hemisphere interpretsIn general, the right hemisphere interprets information and controls actions of the left side ofinformation and controls actions of the left side of the body. The left hemisphere interprets informationthe body. The left hemisphere interprets information and controls actions of the right side of the body. Ifand controls actions of the right side of the body. If the connection between the hemispheres isthe connection between the hemispheres is severed, sensory information cannot pass to thesevered, sensory information cannot pass to the correct region of the brain in order forcorrect region of the brain in order for corresponding response to be made. For examplecorresponding response to be made. For example callosal apraxiacallosal apraxia is a form of limb apraxia causedis a form of limb apraxia caused by damage to the anterior corpus callosum. When aby damage to the anterior corpus callosum. When a person hears a verbal request to perform aperson hears a verbal request to perform a movement, let's say to raise both hands in the air,movement, let's say to raise both hands in the air, the meaning of the speech is analyzed by circuits inthe meaning of the speech is analyzed by circuits in the left hemisphere.the left hemisphere.
  • 12.  Then, a neural command activates the region of theThen, a neural command activates the region of the brain that contains the memory of the movement, thebrain that contains the memory of the movement, the prefrontal cortex.prefrontal cortex.  This information is passed to the part of the brain thatThis information is passed to the part of the brain that controls the actual movement to be performed, thecontrols the actual movement to be performed, the motor cortex.motor cortex.  The left motor cortex controls the movements of theThe left motor cortex controls the movements of the right hand, and the right motor cortex controls theright hand, and the right motor cortex controls the movements of the left hand. In order for the right motormovements of the left hand. In order for the right motor cortex to be activated so that the left hand can becortex to be activated so that the left hand can be raised, the analysis of the verbal command must beraised, the analysis of the verbal command must be passed from the left hemisphere to the right side,passed from the left hemisphere to the right side, through the corpus callosum. Thus, the right arm canthrough the corpus callosum. Thus, the right arm can perform the requested movement, but the left cannot.perform the requested movement, but the left cannot.
  • 13.  So, say a "typical" split-brain patient is sittingSo, say a "typical" split-brain patient is sitting down, looking straight ahead and is focusingdown, looking straight ahead and is focusing on a dot in the middle of a screen. Then aon a dot in the middle of a screen. Then a picture of a spoon is flashed to the right ofpicture of a spoon is flashed to the right of the dot. The visual information about thethe dot. The visual information about the spoon crosses in the optic chiasm and endsspoon crosses in the optic chiasm and ends up in the LEFT HEMISPHERE. When theup in the LEFT HEMISPHERE. When the person is asked what the picture was, theperson is asked what the picture was, the person has no problem identifying the spoonperson has no problem identifying the spoon and says "Spoon." However, if the spoon hadand says "Spoon." However, if the spoon had been flashed to the left of the dot (see thebeen flashed to the left of the dot (see the picture), then the visual information wouldpicture), then the visual information would have traveled to the RIGHT HEMISPHERE.have traveled to the RIGHT HEMISPHERE.
  • 14. Visual fieldVisual field
  • 15.  Now if the person is asked what the picture was, theNow if the person is asked what the picture was, the person will say that nothing was seen!! But, when thisperson will say that nothing was seen!! But, when this same person is asked to pick out an object using onlysame person is asked to pick out an object using only the LEFT hand, this person will correctly pick out thethe LEFT hand, this person will correctly pick out the spoon. This is because touch information from thespoon. This is because touch information from the left hand crosses over to the right hemisphere - theleft hand crosses over to the right hemisphere - the side that "saw" the spoon. However, if the person isside that "saw" the spoon. However, if the person is again asked what the object is, even when it is in theagain asked what the object is, even when it is in the person's hand, the person will NOT be able to sayperson's hand, the person will NOT be able to say what it is because the right hemisphere cannot "talk."what it is because the right hemisphere cannot "talk." So, the right hemisphere is not stupid, it just has littleSo, the right hemisphere is not stupid, it just has little ability for language - it is "non-verbal."ability for language - it is "non-verbal."
  • 16.  Another type of experimentAnother type of experiment performed with split brainperformed with split brain patients uses chimericpatients uses chimeric figures, like this one to thefigures, like this one to the right. In this figure, the faceright. In this figure, the face on the left is a woman andon the left is a woman and the face on the right is athe face on the right is a man. Therefore, if the patientman. Therefore, if the patient focuses on the dot in thefocuses on the dot in the middle of the forehead, themiddle of the forehead, the visual information about thevisual information about the woman's face will go to thewoman's face will go to the right cerebral hemisphereright cerebral hemisphere and information about theand information about the man's face will go to the leftman's face will go to the left hemispherehemisphere
  • 17.  When a split brain patient is askedWhen a split brain patient is asked to point to a whole, normal pictureto point to a whole, normal picture of the face that was just seen, theof the face that was just seen, the patient will usually pick out thepatient will usually pick out the woman's picture (remember, thewoman's picture (remember, the information about the woman'sinformation about the woman's face went to the RIGHT cerebralface went to the RIGHT cerebral hemisphere). However, if thehemisphere). However, if the patient is required to say whetherpatient is required to say whether the picture was a man or a woman,the picture was a man or a woman, the patient will SAY that the picturethe patient will SAY that the picture was of a man. Therefore,was of a man. Therefore, depending on what the patient isdepending on what the patient is required to do, either the right orrequired to do, either the right or left hemisphere will dominate. Inleft hemisphere will dominate. In this case, when speech is notthis case, when speech is not required, the right hemisphere willrequired, the right hemisphere will dominate for recognition of facesdominate for recognition of faces
  • 18. The undivided brainThe undivided brain  So what about the 99.99 percent of us withSo what about the 99.99 percent of us with undivided brains? Have scientist found ourundivided brains? Have scientist found our hemispheres to be similarly specialized? Yeshemispheres to be similarly specialized? Yes they have in several different types of studies.they have in several different types of studies. For example, when a person performs aFor example, when a person performs a perceptual task, brain waves, blood flow, andperceptual task, brain waves, blood flow, and glucose consumption reveal increased activityglucose consumption reveal increased activity in the right hemisphere; when a person speaksin the right hemisphere; when a person speaks or calculates, activity increases in the leftor calculates, activity increases in the left hemisphere.hemisphere.
  • 19. Cerebral DominanceCerebral Dominance  Each hemisphere of the brain is dominant for otherEach hemisphere of the brain is dominant for other behaviors. For example, it appears that the rightbehaviors. For example, it appears that the right brain is dominant for spatial abilities, facebrain is dominant for spatial abilities, face recognition, visual imagery and music. The leftrecognition, visual imagery and music. The left brain may be more dominant for calculations, mathbrain may be more dominant for calculations, math and logical abilities. Of course, these areand logical abilities. Of course, these are generalizations and in normal people, the twogeneralizations and in normal people, the two hemispheres work together, are connected, andhemispheres work together, are connected, and share information through the corpus callosum..share information through the corpus callosum..
  • 20.  LeftLeft HemisphereHemisphere   LanguageLanguage  MathMath  LogicLogic  RightRight HemisphereHemisphere   Spatial abilitiesSpatial abilities  Face recognitionFace recognition  Visual imageryVisual imagery  MusicMusic
  • 21. DominanceDominance  Are you right-handed or left-handed? As youAre you right-handed or left-handed? As you probably know, most people (about 90% of theprobably know, most people (about 90% of the population) are right-handed - they prefer topopulation) are right-handed - they prefer to use their right hand to write, eat and throw ause their right hand to write, eat and throw a ball. Another way to refer to people who useball. Another way to refer to people who use their right hand is to say that they are "righttheir right hand is to say that they are "right hand dominant." It follows that most of thehand dominant." It follows that most of the other 10% of the population is left-handed orother 10% of the population is left-handed or "left hand dominant." There are few people"left hand dominant." There are few people who use each hand equally; they arewho use each hand equally; they are "ambidextrous." Most people also have a"ambidextrous." Most people also have a dominant eye and dominant ear...dominant eye and dominant ear...
  • 22. Dominant Ear?Dominant Ear?  ear's OAE (otoacoustic emission) .ear's OAE (otoacoustic emission) . Researchers measured the babies OAE with two types ofResearchers measured the babies OAE with two types of sound. First, they used rapid clicks and then sustainedsound. First, they used rapid clicks and then sustained tones. They were surprised to find that the left ear providestones. They were surprised to find that the left ear provides extra amplification for tones like music, while the right earextra amplification for tones like music, while the right ear provides extra amplification for rapid sounds timed likeprovides extra amplification for rapid sounds timed like speech.speech.  "We were intrigued to discover that the clicks triggered"We were intrigued to discover that the clicks triggered more amplification in the baby's right ear, while the tonesmore amplification in the baby's right ear, while the tones induced more amplification in the baby's left ear," saidinduced more amplification in the baby's left ear," said Sininger. "This parallels how the brain processes speechSininger. "This parallels how the brain processes speech and music, except the sides are reversed due to the brain'sand music, except the sides are reversed due to the brain's cross connections."cross connections."  ""
  • 23.  Our findings demonstrate that auditoryOur findings demonstrate that auditory processing starts in the ear before it is everprocessing starts in the ear before it is ever seen in the brain," said Cone-Wesson. "Evenseen in the brain," said Cone-Wesson. "Even at birth, the ear is structured to distinguishat birth, the ear is structured to distinguish between different types of sound and to sendbetween different types of sound and to send it to the right place in the brain."it to the right place in the brain."  Previous research supports the team's newPrevious research supports the team's new findings. For example, earlier researchfindings. For example, earlier research shows that children with impairment in theshows that children with impairment in the right ear encounter more trouble learning inright ear encounter more trouble learning in school than children with hearing loss in theschool than children with hearing loss in the left ear.left ear.