Lateralization

Question 1

Lateralization

Answer 1

Dominance of one hemisphere of cerebral cortex over the other for particular functions

Question 2

Wada Test

Answer 2

determines lateralization

Anesthetize 1 hemisphere by injecting Sodium Amytal in L or R carotid artery

Question 3

right hemisphere

Answer 3

is usually dominant for visio-spatial tasks and socio-emotional processes

Question 4

left hemisphere

Answer 4

is usually dominant for language & other sequential and analytic processes
- Includes manual control: ~90% humans are right-handed, even prehistorically (per early tools, artwork, etc.)

Question 5

Planum Temporale

Answer 5

area in Temporal Cortex (includes Wernicke’s Area) - larger in Left Hemisphere

• In Nonhuman Primates: Equal or only slightly larger in left, also involved in vocal communication

Question 6

slightly larger in Males

Answer 6

Right Cerebral Cortex

Question 7

slightly larger in Females

Answer 7

Left Cerebral Cortex

Question 8

Interference

talking?

stuttering?

Answer 8

can be observed in simultaneous tasks controlled by same hemisphere, or in competition between hemispheres

• e.g. While talking (Left hemi dom), will tap more slowly w/Right hand (Left hemi dom), than w/Left hand (Right hemi dom)
• e.g. Stuttering (most often in left-handers) may involve hemispheric competition for control of speech (don’t have strong lateralization)

Question 9

Corpus Callosum

Answer 9

Bundle of axons connecting 2 cortical hemispheres integrate sensory/motor info from 2 sides

• Thicker in Left Handers (who also tend to be more ambidextrous than right-handers)
• Thicker in Women, who are thus less lateralized (e.g. after damage to one hemi, other more able to take over function)

Question 10

Split-Brain Patients

Answer 10

have Corpus Callosum connections severed - e.g. As treatment for epilepsy

• Word or image flashed in Right Visual Field (=> Left hemi) can be ID’d by touch only by Right hand but not by Left hand
• Image flashed in Right Visual Field (=> Left hemisphere) easily named, but not if in Left Visual Field
• Image (e.g. 5) flashed in Left Visual Field (=> Right hemisphere) and experimenter ask yes/no question
• Sometimes patient’s hands operate independently - e.g. One buttons shirt while other unbuttons it
• Overall, however, behavior fairly normal, subject learns to cope by shifting eyes, hands, talking to self, etc.

Question 11

Image (e.g. 5) flashed in Left Visual Field (=> Right hemisphere) and experimenter ask yes/no question

Answer 11

• e.g. Exp: Is this a letter? Subject: Yes (response produced by ignorant Left hemisphere)
• If incorrect, knowledgeable Right hemisphere => frown, Left detects frown & changes response!

Question 12

Anterior Commisure

larger in?

Answer 12

• connects anterior parts of cerebral cortex, especially the Temporal Lobes
  – Larger in Females and Homosexual Males