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BRAIN ASYMMETRY

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Outline •  Left Brain vs. Right Brain? • Anatomy of the Corpus Callosum • Split Brain •  The Left Hemisphere •  The Right Hemisphere •  Lateralization of Emotion

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Questionnaire 1.  When you work do you: a) do several things at once, all at various

stages, b) do one thing at a time and don’t start new things until first thing is finished?

2.  When you’re working does time a) pass quickly, unnoticed, b) tick slowly, aware of time?

3.  When you try something new do you a) read all you can before you begin, b) jump in and see what happens?

4.  How often do you make a decision based on a hunch a) often, b) rarely? 5.  Do you find it easier to remember someone’s a) name, b) face? 6.  How often are you late for appointments/dates a) very rarely, b) all the

time? 7.  Do you judge a) what people say, b) how they say it? 8.  Do you use your hands when talking a) hardly ever, b) all the time? 9.  Do you have your best ideas when a) lying down, b) sitting up? 10. Do you listen to music while you work a) yes, b) no? 11. When you want to buy something new do you a) buy it only if you have

the money, b) charge it regardless of cost? 12.  If someone asks your opinion of something they did that you don’t like

do you a) think carefully, crafting an answer, b) say exactly what you’re thinking?

13. Before beginning something do you a) have an overall picture of the outcome, b) have it worked out step by step?

14. When hanging a picture on the wall do you a) put it up where it looks right, b) use a measuring tape?

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Questionnaire Give yourself a 1 for each A answer if Brown, 1 for each B answer if Red for Left

dominance score (14 is highest for left; 7 is even hemispheres) Right = Brown ; Left = Red

1.  When you work do you: a) do several things at once, all at various stages, b) do one thing at a time and don’t start new things until first thing is finished?

2.  When you’re working does time a) pass quickly, unnoticed, b) tick slowly, aware of time?

3.  When you try something new do you a) read all you can before you begin, b) jump in and see what happens?

4.  How often do you make a decision based on a hunch a) often, b) rarely? 5.  Do you find it easier to remember someone’s a) name, b) face? 6.  How often are you late for appointments/dates a) very rarely, b) all the time? 7.  Do you judge a) what people say, b) how they say it? 8.  Do you use your hands when talking a) hardly ever, b) all the time? 9.  Do you have your best ideas when a) lying down, b) sitting up? 10.  Do you listen to music while you work a) yes, b) no? 11.  When you want to buy something new do you a) buy it only if you have the

money, b) charge it regardless of cost? 12.  If someone asks your opinion of something they did that you don’t like do you

a) think carefully, crafting an answer, b) say exactly what you’re thinking? 13.  Before beginning something do you a) have an overall picture of the outcome,

b) have it worked out step by step? 14.  When hanging a picture on the wall do you a) put it up where it looks right, b)

use a measuring tape?

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Popular Concept

Left:

• Verbal • Sequential • Logical • Plans ahead • Remembers names • Looks at parts

Right:

• Visual/spatial • Random • Emotional •  Impulsive • Remembers faces • Looks at whole

Is there any evidence to support this?

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Outline •  Left Brain vs. Right Brain? • Anatomy of the Corpus Callosum • Split Brain •  The Left Hemisphere •  The Right Hemisphere •  Lateralization of Emotion

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Most cognitive processes involve the coordination of both hemispheres

• Corpus Callosum •  large bundle of neural

fibers •  connects the two

hemispheres •  carries messages

between the hemispheres

• What kind of matter is it?

• How can we measure it?

Corpus Callosum

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Callosal Projections • Homotopic Connections – link same area • Heterotopic Connections – go to different areas

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Why have homotopic connections? • Animal shown two separate

light bars moving in different directions

• Visual receptive field 1 and 2 are not correlated

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Why have homotopic connections? • Animal shown a common

object that goes across two separate fields.

• Visual receptive field 1 and 2 are synchronized

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Why have homotopic connections? • Severed corpus callosum • Animal shown a common

object that goes across two separate fields.

• Visual receptive field 1 and 2 are not synchronized

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Why have homotopic connections? • Synchronization •  Inhibition

•  Some fibers may be inhibitory •  Hemispheres may compete for control of processing

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Parts of the Corpus Callosum •  Sever Splenium (posterior)

•  transfer of visual, tactile, and auditory sensory info is severely disrupted •  Sever Rostrum/Genu (anterior)

•  higher order transfer of semantic information is disrupted •  How do we know this?

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DTI + fMRI Evidence

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Outline •  Left Brain vs. Right Brain? • Anatomy of the Corpus Callosum • Split Brain •  The Left Hemisphere •  The Right Hemisphere •  Lateralization of Emotion

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Split-brain patients

• Gazzaniga et al. (1962) • Documentary •  http://www.youtube.com/watch?v=MZnyQewsB_Y •  “Joe” •  http://www.youtube.com/watch?

v=aCv4K5aStdU&feature=related • Scientific American Frontiers •  http://www.youtube.com/watch?

v=W9iNMxjxL7k&feature=related • Brain Story BBC documentary •  http://www.youtube.com/watch?v=fCwIhztgTv4

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Our Divided Brain

• Path of information from the eyes to the brain

• Contralateral control

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Fig. 14-4a, p. 420

The word hatband is flashed on a screen 19

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Fig. 14-4b, p. 420

A woman with a split brain can report only what her left hemisphere saw, “band.” The left hemisphere controls the right hand

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Fig. 14-4c, p. 420

However, with her left hand, she can point to a hat, which is what the right hemisphere saw. She can’t say it - but she can point.

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Brain Asymmetry

• Conclusions: • Left brain: language and analytical thought • Right brain: spatial relations and creativity

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Outline •  Left Brain vs. Right Brain? • Anatomy of the Corpus Callosum • Split Brain •  The Left Hemisphere •  The Right Hemisphere •  Lateralization of Emotion

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Handedness and Lateralization • Strong but imperfect correlation between handedness

and lateralization •  http://faculty.washington.edu/chudler/split.html

• Strongest lateralization in right-handed males •  90% of population is right-handed

•  95% of righties use Left hemisphere for language •  10% of population is left-handed

•  70% of lefties use Left hemisphere for language •  30% of lefties use both hemispheres for language

• Problem: How do you define and measure handedness?

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Language on the Left Speech Production:

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Speech Comprehension

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Left Hemisphere: The Interpreter 26

The Interpreter •  The left brain may be important for interpreting what’s

happening.

•  Flash “Stand up” to right hemisphere • Patient will stand up • Ask them why:

•  Left brain says: “I wanted to go get a soda.”

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The Interpreter •  Left hemisphere helps us to make sense of events • OVER-interpreter? •  Left hemisphere can lead us to look for patterns that don’t

exist: •  Have to predict if the red or green light will flash •  If you get it right, you get a reward •  Random sequence of lights, but red light flashes more •  Animals and right hemisphere split brain: always pick red •  Normal humans and left hemisphere split brain: look for some

pattern (which doesn’t exist)

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Outline •  Left Brain vs. Right Brain? • Anatomy of the Corpus Callosum • Split Brain •  The Left Hemisphere •  The Right Hemisphere •  Lateralization of Emotion

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Right Hemisphere Language •  It can understand the meaning of a word

• Comprehend vocabulary at 13 yr level • Comprehend sentence structure at 5 yr level

• Provides an understanding of context of language • Governs Prosody: emotional expression of language •  Important with visual-spatial information

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The right hemisphere can recognize language

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•  Subject says they see nothing (left hemisphere)

•  Can draw with left

hand (right hemisphere)

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The right hemisphere cannot recognize syntax

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Right hemisphere can’t point to the picture of what happens when the words are causally related

The Right Hemisphere: Visual Processes Recognizing Unfamiliar Faces

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Right hemisphere: better at recognizing unfamiliar faces

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Outline •  Left Brain vs. Right Brain? • Anatomy of the Corpus Callosum • Split Brain •  The Left Hemisphere •  The Right Hemisphere •  Lateralization of Emotion

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Facial Expressions • Different brain circuits for facial expressions: • Voluntary Expressions • Spontaneous Expressions

• Which part of the brain do you think is involved in facial expressions?

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Facial Expressions

• Right hemisphere damage – problems with voluntary facial expression

• Parkinson’s Disease Patient – problems with spontaneous facial expressions

Told to smile Spontaneous Smile

Told to smile

Spontaneous Smile

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Chimeric Faces & Split Brain

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Left Brain vs. Right Brain • What do you think? • Does left = analytic/sequential and right = holistic/parallel

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Summary

• Split-brain research provided evidence for • Hemispheric specialization • Corpus callosum integrates info from 2 hemispheres

• One hemisphere more efficient in a cognitive process, not solely responsible

• Difficult to get lateralization effect in normal population •  In part due to handedness? Gender? Other?

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Why did lateralization evolve? • Why do hemispheres specialize? • What are the pros and cons to lateralization?

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