🔑 Key Definitions
Hemispheric Specialization: Different functions lateralized to left or right cerebral hemisphere
Commissurotomy: Surgical cutting of corpus callosum; "split-brain" procedure to treat severe epilepsy
Split-Brain: Condition where hemispheres cannot communicate; allows study of hemisphere specialization
Contralateral Control: Each hemisphere controls opposite side of body and receives input from opposite visual field
Commissurotomy: Surgical cutting of corpus callosum; "split-brain" procedure to treat severe epilepsy
Split-Brain: Condition where hemispheres cannot communicate; allows study of hemisphere specialization
Contralateral Control: Each hemisphere controls opposite side of body and receives input from opposite visual field
📅 Important Historical Figure
- Marc Dax - In 1836, first reported left hemisphere specialization for language based on stroke patients
🧠 Hemispheric Specialization
- Left Hemisphere: Language (Broca's, Wernicke's areas), analytical thinking, sequential processing, math
- Right Hemisphere: Spatial abilities, face recognition, emotional prosody, holistic processing, music
- Language Dominance: ~95% of people have language in left hemisphere (most right-handers and many left-handers)
🧠 Split-Brain Research
- Commissurotomy: Cut corpus callosum to prevent seizure spread; creates "two brains"
- Visual Field Tests: Left visual field → right hemisphere, right visual field → left hemisphere
- HEART Experiment: HE flashed to left visual field (right hemisphere), ART to right field (left hemisphere); patient reports seeing "ART" (language hemisphere) but points to "HE" with left hand (controlled by right hemisphere)
- Disconnection: Each hemisphere has information the other doesn't; can't verbally report right hemisphere perceptions
🧠 Handedness & Brain Dominance
- Right-Handers (~90%): Almost all (95%+) have left hemisphere language dominance
- Left-Handers (~10%): About 70% still have left hemisphere language; 15% right; 15% bilateral
- Not Absolute: Handedness doesn't perfectly predict language lateralization
💡 Exam Tips
- Marc Dax (1836) first identified left hemisphere language specialization
- Left = language, analytical; Right = spatial, holistic
- Split-brain = cut corpus callosum = two independent hemispheres
- HEART experiment demonstrates hemispheric independence after split-brain surgery
- Visual fields cross: left field → right hemisphere, right field → left hemisphere
- Language dominance: ~95% in left hemisphere overall