Chapter 11/12 Cerebral Asymmetry

Question 1

Define Laterality

Answer 1

idea that the two cerebral hemispheres have separate functions which leads to idea that two different minds control our behaviour

Question 2

what are the 5 variables that complicate research on laterality

Answer 2

Relative, not absolute
cerebral site as important as understanding function as cerebral side
environmental and genetic factors
range of animal exhibit
we act as though we are single minded

Question 3

Explain relative, not absolute

Answer 3

although one side can be more important in a function, the other hemisphere is still involved

Question 4

explain environmental and genetic factors

Answer 4

females and left handers appear to be less asymmetric than right handers and males

Question 5

explain cerebral site as important as understanding function as cerebral side

Answer 5

best to think of cortical functions as being partially localized and the hemisphere side is just one feature of the localization

Question 6

explain range of animal exhibit

Answer 6

certain animals (monkeys, songbirds) also have functionally and anatomically asymmetrical brains even though they are not identical to humans

Question 7

explain we act as though there is a single mind

Answer 7

although each hemisphere is specialized, we normally act as though there is a single cognitive processor

Question 8

8 major anatomical differences between 2 hemispheres

Answer 8

1. RH = larger and heavier while LH has more white matter
2. structural differences provide anatomical basis for specialization in language and music
3. correlates with asymmetry of thalamus, left is dominant for language in thalamus
4. slope of lateral fissure is gentler on LH
5. Broca’s area is organized diff on left and right. 1/3 larger on right, left affects grammar
6. distribution of nts are asymmetrical
7. RH extends further anterior, LH extends posterior. lateral ventricles x5 longer on RH
8. thicker cortex in LH, but larger SA in RH

Question 9

what about neuronal asymmetry in the 2 hemispheres

Answer 9

the more branching points, allow the cell more degrees of freedom with respect to its function
abundant branches in Broca’s area

Question 10

What about genetic asymmetry in the 2 hemispheres

Answer 10

found genes that are expressed differently in each hemisphere and that epigenetic changes likely influence each hemisphere differently

Question 11

Applying electrical current to the cortex of a conscious patient has 4 general effects (___ excitatory and ___ inhibitory)

Answer 11

3 excitatory and 1 inhibitory
1. brain has symmetrical and asymmetrical
2. RH has perceptual functions not shared by LH = stimulation of RH produces phenomena (of alterations in patients interpretation of surroundings) much more frequently than LH
3. stimulating L frontal or temporal accelerate speech production
4. stimulation blocks function = inhibitory affect is apparent only when the patient is actively engaged in those behaviours

Question 12

Explain double dissociation experiment

Answer 12

LH lesions produce deficits in language that are not produced by RH lesions.
Performing spatial tasks are disrupted by RH lesions, but not LH.
Bc RH lesions disturb tasks not disrupted by LH and vise versa, two hemispheres are doubly dissociated

Question 13

Define commissurotomy

Answer 13

surgical procedure of disconnecting two hemispheres of the corpus callosum (bc of epileptic seizure meds not working)

Question 14

problems resulting from commissurotomy

Answer 14

the brain cannot join together the two different views of the L and R

Question 15

What is the interpreter

Answer 15

split-brain patients are presented with two images, asked to select a third image to match the scene. Each hand chooses an option appropriate to the scene, but when asked to explain the choice, answers based on the right hand in terms of right scene

Question 16

What is the Wada Test

Answer 16

using carotid sodium amobarbital injection
shows 98% of right handers and 70% of left handers show speech disturbance after sodium injection into LH but not after RH

Question 17

explain asymmetry in visual system

Answer 17

allows for selective presentation of visual info to each hemisphere of the brain
LH better at processing verbal info while RH is better at processing visual faces

Question 18

explain asymmetry in auditory systems

Answer 18

both hemispheres receive info from both ears
found people remembered more info from right ear than left because it has a shorter path to travel
LH processes language part of music, RH excels with musical stimuli

Question 19

explain asymmetry in somatosensory system

Answer 19

has crossed nature
found R hand advantage for identifying letters (because would be LH) and L hand advantage for other shapes

Question 20

explain asymmetry in motor systems

Answer 20

sensory input processing isnt equal on both sides, it is difficult to study motor control differences

Question 21

what are the two main methods to figure out motor asymmetries

Answer 21

1. direct observation
2. inference tasks

Question 22

What is direct observation task for motor asymmetries

Answer 22

watching people move in their everday life
found right side of mouth moves more when talking, therefore left side has more control in this
found use right hand more when talking but left for other things

Question 23

what is inference tasks for motor asymmetries

Answer 23

doing two complex tasks at once
different sides of the brain handle multitasking differently
each side of the brain seems to have its own strengths in movement

Question 24

what is the correlation problem with laterality studies about brain function

Answer 24

the behavioural tasks don’t always match with the brain tests.
maybe because behavioural tasks measure more than just which side of the brain in dominant in a task

Question 25

Define extreme unilateral specialization

Answer 25

suggests each hemisphere has distinct specialized functions

Question 26

Explain what the thoughts are on how the hemispheres process information differently

Answer 26

left = more analytical and sequential
right = holistic and integrated

Question 27

What is the interaction model

Answer 27

that both brain hemispheres can handle all functions but typically dont

Question 28

What are the 3 reasons for the interaction model

Answer 28

1. simulation processing = both hemispheres work together but focus on different aspects of processing
2. inhibitory interaction = each hemisphere suppresses the function of the other
3. Selective attention and analysis = each hemisphere pays attention to different information. If one is overloaded, the other can help

Question 29

is lateralization of the brain unique to humans

Answer 29

no