HEMISPHERIC SPECIALIZATION

Question 1

Language

Asymmetries

Answer 1

• Language typically in left hemisphere
– 96% of right-­handers are left‐hem dominant for language
– 60% of left‐handers are left‐hem dominant for language

• Anatomical correlation:
65% of brains have larger planum temporale
(houses Wernicke’s area) in left hem

• Semantic/Syntax is left hem lateralized,
but prosody/emotional content is right hem lateralized

Question 2

Language Asymmetries:

Wada Test

Answer 2

– To determine hemisphere language is in prior to surgery
– Inject amobarbitol (anesthetic) into left or right carotid artery
– When injected into hemisphere that processes language, patient loses ability to understand or produce speech for several minutes

Question 3

Right Hemisphere Dominance

Answer 3

– Better visuospacial processing
– Better face processing
(FFA also typically more robust in right hem)
– Spatial attention (neglect)
– Left motor, left visual field

Question 4

Left Hemisphere Dominance

Answer 4

– More language

– Right motor, right visual field

Question 5

Exaggerated Asymmetries

Answer 5

Left hem = analytical

Right hem = creative

Question 6

How do the hemispheres communicate?

Answer 6

Via the Corpus Callosum, a giant bundle of white matter

Question 7

Split-­brain Patients

Answer 7

• Callosotomy (split brain surgery)
– Sever corpus callosum
– To treat epilepsy

• W.J.
– Epilepsy; surgery in 1961
– No change in personality
– Could name and describe visual information presented to his left hemisphere, but not right
– Other strange effects

• “Ring” presented in right visual field&raquo_space;> left hem&raquo_space;> language&raquo_space;> say “ring”

• “Key” presented in left visual field&raquo_space;> right
hem&raquo_space;> no language&raquo_space;> denies seeing
anything but left hand correctly retrieves key

• Task: arrange blocks into pattern
– Left hand (right brain):
could arrange easily
– Right hand (left brain):
failed every time
– Left & right hands “fighting” with each other