Functional Lateralization

Question 1

What is laterality?

Answer 1

there are two cerebral hemispheres with separate functions

Question 2

Laterality is…

Answer 2

relative, not absolute

Question 3

Hemispheres play a role in…

Answer 3

all behaviours but one is more dominant

Question 4

What affects laterality?

Answer 4

Environmental and genetic factors

Question 5

In 1860 who made the first observations?

Answer 5

Hughlings-Jackson and Pierre Gratiolet

Question 6

What were Hughlings-Jackson’s and Gratiolet’s findings?

Answer 6

cortical convultions on the LH mature more rapidly than those on the RH

Question 7

Observations were largely ignored until…

Answer 7

1960’s when Geschwind and Levitsky renewed interest

Question 8

How many anatomical differences have been confirmed?

Answer 8

8

Question 9

The first anatomical differences is…

Answer 9

RH slightly larger/heavier, LH has more grey matter

Question 10

The second anatomical difference is…

Answer 10

marked structural asymmetry between temporal lobes

Question 11

The third anatomical difference is…

Answer 11

asymmetry in the cortex of temporal lobes correlates to midbrain asymmetry in the thalamus

Question 12

the fourth anatomical difference is…

Answer 12

slope of lateral fissure gentler in LH

Question 13

the fifth anatomical difference is…

Answer 13

Frontal Operculum organised differently in LH

Question 14

The sixth anatomical difference is…

Answer 14

distribution of various neurotransmitters asymmetrical both in cortical and subcortical regions

Question 15

The seventh anatomical difference is…

Answer 15

RH extends farther anteriorly, LH extends farther posteriorly. Five times more likely that the occipital horns of the lateral ventricles are longer on the RH

Question 16

The eighth anatomical difference is…

Answer 16

details of anatomical asymmetry affected both by sex and handedness

Question 17

Cerebral asymmetry was first established how?

Answer 17

studying patients with neurological disease lateralised to one hemisphere e.g. epilepsy

Question 18

How do we conclude a cortical area is specialised?

Answer 18

Demonstrate lesions in other areas don’t produce a similar deficit.

Question 19

What is double dissociation?

Answer 19

two areas of the neocortex are functionally dissociated by two behavioural tests, each test being affected by a lesion in one area but not the other

Question 20

Examples of double dissociation are…

Answer 20

LH lesions result in deficits in language functions

RH lesions result in deficits in spatial tasks

Question 21

What is Jun Wada credited with?

Answer 21

Injecting sodium amobarbital into the carotid artery creating anaesthesia of the ipsilateral hemisphere - the Wada test

Question 22

When is the Wada test typically used?

Answer 22

before surgery in epileptic patients to establish language dominant hemisphere

Question 23

Brenda Milner demonstrated…

Answer 23

98% right handers are LH language dominant
70% of left handers are LH language dominant
2% of right handers are RH language dominant
15% of left handers are RH language dominant
15% of left handers are bilateral language dominant

Question 24

What are commissurotomy studies?

Answer 24

Split brain studies

Question 25

In the 1940s a common procedure to treat epileptic seizures was...

Answer 25

cutting the Corpus Callosum or the Anterior Commissure - with no severe deficits

Question 26

In the 1950s who severed the Corpus Callosum of cats and monkeys?

Answer 26

Sperry

Question 27

What did Sperry do in the 1950s?

Answer 27

Using visual discrimination found that information never crossed to the other hemisphere.

Question 28

What's the role of the Corpus Callosum?

Answer 28

allows cortical areas from one hemisphere to communicate with cortical areas of the other hemisphere

Question 29

In the 1960s what technique did Vogel and Bogen use?

Answer 29

tachistoscopic presentation

Question 30

What have language studies shown?

Answer 30

Flashing a word to the RVF split-brain patients can say it, but not when it is flashed to the LVF, but can collect the right object using the left hand

Question 31

What can be concluded from language studies?

Answer 31

LH is responsible for language, RH has reasonable comprehension ability

Question 32

What are spatial organisation studies?

Answer 32

Flash a 3D drawing to the RVF (in split-brain patients) and right hand cannot replicate the drawing, but flashed to the LVF, right hand can.

Question 33

What can we conclude from spatial organisation studies?

Answer 33

RH is responsible for spatial organisation

Question 34

What are perception studies?

Answer 34

illusory contours reveal that human RH can process some things the LH cannot

Question 35

What do synthesis studies show?

Answer 35

there is no synthesis across hemispheres, but each hemisphere is capable of synthesis

Question 36

What has techistoscopic presentation shown in the intact brain?

Answer 36

LH/RVF has an advantage for words | RH/LVF has an advantage for faces and other visuospatial stimuli

Question 37

Using dichotic listening in the auditory system we have found...

Answer 37

LH has an advantage for words and linguistic decisions RH has an advantage for melodies there's no ear advantage for vowels

Question 38

What are the two types of theories?

Answer 38

Specialisation theories and interaction theories

Question 39

What do specialisation models say?

Answer 39

only one hemisphere facilitates a given psychological process LH = more logical RH = primarily a synthesizer

Question 40

What do interaction models say?

Answer 40

both hemispheres have the capacity to perform all functions but do not

Question 41

According to interaction models, what versions exist>

Answer 41

1 - hemispheres function simultaneously but work on different aspects of processing 2- they inhibit or suppress each other's activity 3- they receive information preferentially and perform analyses simultaneously