BRAIN ASYMMETRY. Outline

Transcription

1 2 BRAIN ASYMMETRY 3 Outline Left Brain vs. Right Brain? Anatomy of the Corpus Callosum Split Brain The Left Hemisphere The Right Hemisphere Lateralization of Emotion 1

2 Questionnaire 4 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? 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? 5 2

3 Popular Concept 6 Left: Right: Verbal Sequential Logical Plans ahead Remembers names Looks at parts Visual/spatial Random Emotional Impulsive Remembers faces Looks at whole Is there any evidence to support this? 7 Outline Left Brain vs. Right Brain? Anatomy of the Corpus Callosum Split Brain The Left Hemisphere The Right Hemisphere Lateralization of Emotion 3

4 Most cognitive processes involve the coordination of both hemispheres 8 Corpus Callosum 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? 9 Callosal Projections Homotopic Connections link same area Heterotopic Connections go to different areas 4

5 Why have homotopic connections? Animal shown two separate light bars moving in different directions Visual receptive field 1 and 2 are not correlated 10 Why have homotopic connections? Animal shown a common object that goes across two separate fields. Visual receptive field 1 and 2 are synchronized 11 5

6 Why have homotopic connections? Severed corpus callosum Animal shown a common object that goes across two separate fields. 12 Visual receptive field 1 and 2 are not synchronized Why have homotopic connections? Synchronization Inhibition Some fibers may be inhibitory Hemispheres may compete for control of processing 13 6

7 14 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? DTI + fmri Evidence 15 7

8 16 Outline Left Brain vs. Right Brain? Anatomy of the Corpus Callosum Split Brain The Left Hemisphere The Right Hemisphere Lateralization of Emotion 17 Split-brain patients Gazzaniga et al. (1962) Documentary Joe v=acv4k5astdu&feature=related Scientific American Frontiers v=w9inmxjxl7k&feature=related Brain Story BBC documentary 8

9 18 Our Divided Brain Path of information from the eyes to the brain Contralateral control 19 The word hatband is flashed on a screen Fig. 14-4a, p

10 20 A woman with a split brain can report only what her left hemisphere saw, band. The left hemisphere controls the right hand Fig. 14-4b, p 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. Fig. 14-4c, p

11 22 Brain Asymmetry Conclusions: Left brain: language and analytical thought Right brain: spatial relations and creativity 23 Outline Left Brain vs. Right Brain? Anatomy of the Corpus Callosum Split Brain The Left Hemisphere The Right Hemisphere Lateralization of Emotion 11

12 Handedness and Lateralization 24 Strong but imperfect correlation between handedness and lateralization 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? Language on the Left 25 Speech Production: Speech Comprehension

13 Left Hemisphere: The Interpreter 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. 13

14 28 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) Outline Left Brain vs. Right Brain? Anatomy of the Corpus Callosum Split Brain The Left Hemisphere The Right Hemisphere Lateralization of Emotion 29 14

15 Right Hemisphere Language It can understand the meaning of a word Comprehend vocabulary at 13 yr level Comprehend sentence structure at 5 yr level 30 Provides an understanding of context of language Governs Prosody: emotional expression of language Important with visual-spatial information The right hemisphere can recognize language 31 Subject says they see nothing (left hemisphere) Can draw with left hand (right hemisphere) 15

16 32 The right hemisphere cannot recognize syntax 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 33 Right hemisphere: better at recognizing unfamiliar faces 16

17 34 Outline Left Brain vs. Right Brain? Anatomy of the Corpus Callosum Split Brain The Left Hemisphere The Right Hemisphere Lateralization of Emotion 35 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? 17

18 36 Facial Expressions Told to smile Spontaneous Smile Right hemisphere damage problems with voluntary facial expression Told to smile Parkinson s Disease Patient problems with spontaneous facial expressions Spontaneous Smile 37 Chimeric Faces & Split Brain 18

19 38 Left Brain vs. Right Brain What do you think? Does left = analytic/sequential and right = holistic/parallel Summary 39 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? 19

20 40 Why did lateralization evolve? Why do hemispheres specialize? What are the pros and cons to lateralization? 20