Elevated Prevalence of left handedness in:

1. Autism Schizophrenia Alcoholism Criminals Lawyers Sleep difficulties Stutterers Immune disorders Math prodigies Gifted children Professional tennis & baseball players Recent Presidents Architects Artists Elevated Prevalence of left handedness in:

2. Evolution of Handedness • Nature vs Nuture • Cultural mechanisms • Environmental causes • Genetic causes Right-handedness Other species? Early humans?

4. Evidence from early humans • Preferential wear on many cutting stone tools suggests right handedness • Art for 5,000 years of tool or weapon use • 93% were right-handed when unimanual • no systematic trends through time • Few pieces prior to 3000 BC - Coren & Porac (1977) • Hand outlines • 70% are of the left hand • Biblical evidence • (Judges 20): 700 of 26,000 of children of Benjamin “restricted in use of the right hand” = 2.7% left-handed

5. Causes of Left Handedness • Environmental • Early brain injury • 7.3% in normal elementary schools vs • 18.2 % in special education facilities (in 1920) • 14-14.5 % in twins v 8.5 % in single births (in 1940) • Cultural pressure for right handedness • Genetic • Right Shift Hypothesis • Child’s handedness given parents’ handedness • R-R: 92.4% • R-L: 80.5% • L-L: 45.5 %

6. Left-Handedness Across the Life Span • Proportion of left handers drops with age • 14% of 10-year-olds • 5% of 50-year-olds • < 1% of 80-year-olds • Cause is unknown • Longevity hypothesis • Modification hypothesis

8. Curse or blessing of left-handedness • Possible disadvantages • Left-handers are 6x to die in accident • 4x to die while driving • More likely to have fingers amputated by power-tools, suffer wrist fractures • Lefties more susceptible to allergies, reading disabilities, and migraines • Possible advantages • Lefties are more common among baseball & tennis players, architects and artists • Corpus callosum is 11% greater • Possible greater integration of both brain hemispheres in processing information

10. Brain areas involved in Language

11. Sensory-processingcontralateral pathways

16. Visual Pathway

18. Lateralized Eye Movements • Synonym for walking or intelligence • Define impish or prudish • Which direction does Thomas Jefferson face on the nickel (west/left) • Which states share a border with North Carolina (VA, TN, SC)

19. Lateralized Eye Movements (LEM) • Which way you look tells me (the observer) which brain you activated? • Leftward movement from my perspective indicates LH activation • (RVF squashed so LH will not be distracted when doing the work) • Rightward movement from my perspective means RH is doing the work

20. Street Test of Right Hemisphere Dominance

22. Mooney (1957) – ID age & gender

23. Left hemisphere dominance

24. Orange Coat Wagon Wood Egg Poem Fly Banana Dress Bicycle Alcohol Seed Statue Tree Similarities Test (selected items)

25. Left Hemisphere • Right hand touch and movement • Analytical processing • Verbal skills • Speech, writing

26. Right Hemisphere • Left hand touch and movement • Holistic & Nonverbal processing including emotional tone and content • Spatial processing • Face recognition

27. Neuroimaging methods • STRUCTURAL =density differences • CT (Computerized Tomography) • MRI (Magnetic resonance imaging) • Combines slices for 3-D image • FUNCTIONAL = electrical activity, blood flow, oxygenation • EEG (Topography) 1929 • MEG (Magnetoencephalogram) • TMS (Transcranial Magnetic Stimulation) • PET (Positron Emission Tomography) 1970 • Measure of cerebral glucose level • Advantages: high spatial resolution • Disadvantages: somewhat invasive • fMRI (functional MRI) 1990

28. Positron Emission Tomography (PET) (blood flow)

29. Structural MRI (gray matter thickness map) Functional MRI (activation to music) Diffusion Tensor MRI (white matter tracts) MRI examples Anatomical MRI (T2-weighted) Anatomical MRI (T1-weighted) Noisy & Claustrophobic

30. Electroencephalography (EEG) – Brainwaves

31. 10 8 6 4 2 0 Neuroimaging Spatiotemporal resolution Optical Imaging MEG / EEG Spatial Resolution (mm) PET fMRI MRI Single / Multi Unit Recording 1 msec 1 sec 1 min 10 min 1 hour Temporal Resolution (sec)