Chapter 4 Hemispheric Specialization

Question 1

Somatosensation Projections to the contralateral hemisphere

Answer 1

• Blue pathways (precise touch, kinesthesia) begins ipsilateral until it passes the midbrain
• Red pathways (pain, temperature) cross over and travel contralateral immediately in the spinal cord
• Both pass through the thalamus before going to the primary somatosensory cortex

Question 2

Motor cortex controls contralateral muscles

Answer 2

• Descending motor pathway

- As it crosses brainstem moves to the contralateral side

Question 3

Front facing eyes vs side facing eyes (predator vs. prey)

Answer 3

• For side facing eyes all vision is contralateral
• Front facing eyes information from the left visual field ends up in the right primary visual cortex regardless of which eye its being detected by and information from the right visual field ends up in the left primary visual cortex
• Crosses over at the optic chiasm
• Not based on eye, but on field

Question 4

Wada Test

Answer 4

• Test what the two hemispheres are capable of independently
• Done by injecting drug (amobarbital, GABA agonists, sedative) into the common carotid artery

Question 5

Wada Test: What happens when you put the right hemisphere to sleep?

Answer 5

• you can carry on conversation,
• Normal memorization
• Test for medical purposes to determine normal vs, unusual lateralization of function before operating
• Left hemisphere in the vast majority of people is much more involved in language
• Right hemisphere, implicit memory?
• Only done when there is a medical reason

Question 6

Wada Test: What happens when you put the left hemisphere to sleep?

Answer 6

• the person loses ability to communicate, understand, talk
• They experience amnesia when asked about memory
• If you test in ways that don’t use language, such as pointing, it is evident that they remember

Question 7

Broca’s Area

Answer 7

• Left inferior frontal lobe
• Paul Broca
• involved in the expressive aspects of spoken and written language

Question 8

Wernicke’s Area

Answer 8

• Left Superior temporal gyrus
• German guy
• responsible for language development and comprehension of speech

Question 9

Where does each hemisphere tend to be bigger?

Answer 9

• The right hemisphere tends to be a little bigger in the front anterior
• The left hemisphere tends to be a little bigger in the back posterior

Question 10

Differences in the Sylvian Fissure and the Planum Temporale among the hemispheres

Answer 10

• The shape of the sylvian fissure
  
  • Tends to be more curled
    in the right hemisphere
  • Tends to be flatter in the
    left hemisphere
• Planum Temporale
  
  • 2/3 of people is larger in
    left hemisphere in the
    right (controversial)

Question 11

Differences in cells among the hemispheres

Answer 11

• Right hemisphere
  
  • The cells tends to be
    smaller
• Left hemisphere
  
  • Cells are More spread
    out with fewer
    connections
  • Maybe making more
    specific connections

Question 12

3 parts of the Corpus Callosum

Answer 12

Anterior=genu
Middle=body
Posterior=splenium

Question 13

What happens when you damage certain parts of the corpus callosum?

Answer 13

• If you damage the genu, frontal lobes cant talk to each other
• If you damage the splenium, occipital lobes cant talk to each other

Question 14

Homotopic and Heterotopic connections in the corpus callosum

Answer 14

• Homotopic
  
  • Left area A projects to
    Right area A
  • Most connections are
    homotopic
• Heterotopic
  
  • Left area A projects to
    Right area B and left area
    B
  • Ipsilateral connections
    are mirrored
    contralaterally

Question 15

Illusions of unity

Answer 15

• All of us have this sense of a unitary I
• This is probably an illusion
• Different areas of the brain are doing different things and can disagree with each other

Question 16

Language and Hemispheres

Answer 16

• Surprising the right brain can read and figure out language
• Left hemisphere is dominant for language but the right hemisphere can also decipher language

Question 17

Interpreter at work

Answer 17

When the left hemisphere does not know why the left hand is pointing to the shovel, it confabulates a story “you need shovels to clean at chicken coops”

Question 18

Left Hemisphere as Interpreter

Answer 18

• Finding patterns externally and internally
• Trying to make sense of the world externally and internally
• Confabulation

Question 19

Causal perception

Answer 19

• Understanding relationships between cause and effect; interpreting what you saw; seeing a pool ball going into the hole
• Right hemisphere has an advantage for causal perception

Question 20

Causal inference

Answer 20

• Inferring the relationship between cause and effect; hearing a crash and finding a cup on the floor and a cat on the table
• Right hemisphere is terrible at causal inference
• Left hemisphere excels at causal inference

Question 21

Matching behavior

Answer 21

• Behavior matches the probability of a random event (1/4 right lever vs ¾ left lever)
• Humans usually do this
• left hemisphere exhibits this

Question 22

Maximizing behavior

Answer 22

• The better strategy to getting more
• Pulling left lever all of the time
• rats usually do this
• right hemisphere exhibits this

Question 23

Partial Corpus Callosotomy

Answer 23

• Since it Is permanent surgeons may try save some of the corpus callosum
• Partial split
  
  • In this case splenium
    (posterior)
  • This cut blocks the
    visual cortex
  • Some information is able
    to cross
    
    • Higher order
      cognitive, sensory, and
      abstract information

Question 24

Visuopatial tasks

Answer 24

• the right hemisphere is better
• Right hemisphere and left hand could solve
• Left hemisphere and right hand could not solve
• When both hands were used, they fought over dominance in solving the problem
• Alien hand syndrome
  
  • People feel as if they are
    not in control of their
    hand

Question 25

Facial Recognition

Answer 25

- Right hemisphere dominates in facial recognition - better at recognizing familiar other face - Left hemisphere shines at recognizing its own face

Question 26

Local features versus Global Features

Answer 26

- Right hemisphere better at global - Tonality of voice i.e. sad, happy (global) - Left hemisphere better at local - Words and meanings of sentences (local)

Question 27

Brain damage in respect to local and global features

Answer 27

- Right hemisphere damage - Only local structure, loss of global structure - Left hemisphere damage - Only global structure, loss of local structure