Chapter 3

1. Chapter 3 Biological Bases of Behavior

2. Corpus Callosum Our Divided Brain • Corpus Callosum • largest bundle of neural fibers • connects the two brain hemispheres • carries messages between the hemispheres • Lateralization • Hemispheric specialization

3. Our Divided Brain • Contralateral control • Path of information from the eyes to the brain: • Left visual field to right hemisphere • Right visual field to left hemisphere

4. How to study brain lateralization • Case-study approach: Split-brain patients • Severed corpus callosum due to epilepsy • Tasks: • Motor • Speech • Visual • Tactile

5. Brain Lateralizationhttp://faculty.washington.edu/chudler/split.html • Question: • Can patient recognize stimuli presented visually? • Method: • Asked to name words or pictures flashed on a screen • IV: side of screen • Results: • Right side of screen  left hemisphere  say word • Left side of screen  right hemisphere  “huh?” • Conclusions: • Left brain: language and analytical thought • Right brain: spatial relations and creativity • Hemispheric specialization = separate functions for each side

6. Left Brain, Right BrainAre you left or right brained? • Left: • Verbal • Sequential • Logical • Plans ahead • Remembers names • Looks at parts • Right: • Visual/spatial • Random • Emotional • Impulsive • Remembers faces • Looks at whole http://www.playcranium.com Cranium: “The game for your whole brain”

7. Heller & Levy (1981) • Which face is happier?

8. Heller & Levy (1981) • Hypothesis • LVF (left visual field) dominates discrimination of facial emotion • Greater lateralization for righties vs lefties • Method • 12 right-handed & 12 left-handed Ss • Task: Which face looks happier? • “Chimeric faces” presented for 150ms • Result • LVF preference for discrimination (or perception) of facial emotion for righties, not lefties • But, lots of variability between Ss for hemispheric specialization

9. Handedness and Lateralization • Way you are lateralized depends (in part) on handedness • 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 • How would you define and measure handedness?

10. Handedness Tests • Fold your hands (lace fingers). • Which thumb is outermost? • Draw a circle. Now do it with other hand. Now do it with both hands. • Which hand was used first? Which hand drew a better circle? • Stand up and hop on one leg. • Which leg was used? • Write your name with your best penmanship. • What is direction of head tilt (opposite eye is dominant)?

11. Summary of Lateralization • Split-brain research provided evidence for • Hemispheric specialization • Corpus callosum integrates 2 hemispheres • One hemisphere more efficient in cognitive process, not solely responsible • Difficult to get lateralization effect in normal population • In part, due to variability between people? • Why study lateralization? • Final questions: • Why do hemispheres specialize? • Is it better to use more or less of your brain?

12. Questions • Why study brain lateralization (or also called hemispheric specialization)? • Why is the case study approach (studying split-brain patients) not ideal? • Why don’t we (with “normal” intact brains) notice left-right specialization?

13. Questionnaire • 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? • When you’re working does time a) pass quickly, unnoticed, b) tick slowly, aware of time? • When you try something new do you a) read all you can before you begin, b) jump in and see what happens? • How often do you make a decision based on a hunch a) often, b) rarely? • Do you find it easier to remember someone’s a) name, b) face? • How often are you late for appointments/dates a) very rarely, b) all the time? • Do you judge a) what people say, b) how they say it? • Do you use your hands when talking a) hardly ever, b) all the time? • Do you have your best ideas when a) lying down, b) sitting up? • Do you listen to music while you work a) yes, b) no? • When you want to buy something new do you a) buy it only if you have the money, b) charge it regardless of cost? • 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? • Before beginning something do you a) have an overall picture of the outcome, b) have it worked out step by step? • When hanging a picture on the wall do you a) put it up where it looks right, b) use a measuring tape?

14. Questionnaire Give yourself a 1 for each A answer if Blue, 1 for each B answer if Redfor Left dominance score (14 is highest for left; 7 is even hemispheres) Right = Blue ; Left = Red • 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? • When you’re working does time a) pass quickly, unnoticed, b) tick slowly, aware of time? • When you try something new do you a) read all you can before you begin, b) jump in and see what happens? • How often do you make a decision based on a hunch a) often, b) rarely? • Do you find it easier to remember someone’s a) name, b) face? • How often are you late for appointments/dates a) very rarely, b) all the time? • Do you judge a) what people say, b) how they say it? • Do you use your hands when talking a) hardly ever, b) all the time? • Do you have your best ideas when a) lying down, b) sitting up? • Do you listen to music while you work a) yes, b) no? • When you want to buy something new do you a) buy it only if you have the money, b) charge it regardless of cost? • 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? • Before beginning something do you a) have an overall picture of the outcome, b) have it worked out step by step? • When hanging a picture on the wall do you a) put it up where it looks right, b) use a measuring tape?