Lateralisation , Language & Split Brain

Question 1

Aphasia

Answer 1

Deficit in language comprehension or production due to brain damage

Question 2

Broca

Answer 2

Reported results of post mortem examination of two aphasic patients
-patients with deficits in Lang (not able) general sensory motor or intellectual dysfunction
Both had left hemisphere damage centred in left pre frontal
Lobe
Known as broas area

Question 3

Apraxia

Answer 3

Difficulty performing movement s with either side of the body when asked to do so
Liepmann discovered associated with left hemisphere damage
Right hemisphere became dominant
More activity in left than right during language

Question 4

Test of cerebral Laterlisation

Answer 4

95% of right handed participants are left hemisphere dominant for speech
70% of left are also left hemisphere dominant
However damage can cause right to become dominant

Question 5

Split brain experiment Background

Answer 5

In 1953 Myers and speedy performed experiment on cats
Provided means of comparing the function of two hemispheres
To reveal the function of the corpus callosum- transfers learned info from one hemisphere too other, when cut functions independently

Question 6

Split brain experiment 4 cats

Answer 6

Corpus callosum severed
Optic chain severed
Corpus and optic severed
Intact controls

Question 7

Split brain (experiment)

Answer 7

Phase 1 cats learned a lever press pattern discrimination task with a patch over an eye
Phase 2 switched to other eye
Groups 1,2 and 4 performance kept same
In contrast group 3 , the optic chiasm and callosum severed group acted as if the task were completely new to them

Question 8

Split brain experiment (conclusion)

Answer 8

Has capacity as two separate fore brains , each capable of independent learning and of storing its own memories
Function of corpus callosum is to carry info between hemispheres
Best way to study is to use a method to limit info to one hemisphere

Question 9

Tests of split brain patients

Answer 9

First serve corpus callosum was 1940 due to epilepsy to help to reduce severity
Is effective and appeased to have few obvious effects
-visual stimuli are flashed to the right or left of fixation point
Also tactual info is presented to one hand under a ledge

Question 10

Two independent streams of consciousness (L Hemi)

Answer 10

Object presented to the left hemisphere either by touching with right hand
-viewing something in RVF
The patient able to:
-pick out the correct object with right hand
-but could not pick out th correct object with left hand
-could name correct object

Question 11

Two independent streams of consciousness (R Hemi)

Answer 11

Object presented to right hemisphere
-touching something with left hand
-Viewing something in left visual field
The patients could:
-could pick out the correct object with left hand
-not not pick correct with right l
Claimed nothing was presented

Question 12

Cross Cuing

Answer 12

Communication between hemisphere by nonneural route
50% guessing chance (red or green light flashes in LVF)
Guy did perfect - Conclusion
The right hemisphere heard incorrect guess from left and signalled it was wrong by shaking head

Question 13

Learning two things at once

Answer 13

Split brains capable

If split is visually presented two objects at same time , he can reach into two bags and pick the correct item

Question 14

Helping Hand Phenomenon

Answer 14

Occurs when to two hemispheres are presented with different info about correct choice, then asked to reach out and pick object
Usually right hand will chose what left hemisphere saw , but what right sees is an error and makes left hand grab right and pull it over to other object

Question 15

Differences in left and right hemispheres

Answer 15

Language is the most lateralised of all abilities;the left hemi is better than the right at most language related tasks

• right hemisphere is able to understand single written and spoken words
• right Hemi better at task involving spatial ability, emotional stimuli and music tasks

Question 16

Hemispheres engage in different types of memory processing

Answer 16

LH attempts to place it’s experience in larger context
RH attends strictly to the gestalt perceptual characteristics of the stimulus
This is usually termed analytical (LH) versus holistic (RH)
This RH should not be regarded as minor

Question 17

Three theories of Cerebral Asymmetry

Answer 17

Analytic synthetic theory
Motor theory
Linguistic theory

Question 18

Analytic-Synthetic theory

Answer 18

Suggest that there are two fundamentally different modes of thinking , an analytic mode (LH) and synthetic mode (RH)
Neural circuitry is fundamentally different for each
-LH operates in logical, sequential, analytic fashion
RH makes immediate, overall synthetic judgements

Question 19

Motor theory

Answer 19

Suggest LH is specialised for fine motor movement of which speech is but one example - Evidence :
Lesions of the LH disrupt facial movements more than do RH lesions even when they are not related to speech
-Degree of disruption of non verbal facial movements is positively correlated with the degree of aphasia

Question 20

Linguistic Theory

Answer 20

Primary function of LH is language; based on studies of deaf people who communicate using SL this ability is lost if people suffer damage to LH , even if the are able
To make movements required

Question 21

Broca’s Area

Answer 21

Inferior left prefrontal love in left hemisphere
Damage leads to deficits primarily speech production but also comprehension
Characterised by inability to initiate well articulated conversational speech
Common cause stroke

Question 22

Wernickes Area

Answer 22

Left temporal lobe , just posterior to the primary auditory cortex in the superior temporal gyrus
Damage leads to semantic language comprehension
Also speech is incomprehensible , despite having correct grammar , rhythm and intonation
Recovery is possible after stroke

Question 23

Other disorders of speech production

Answer 23

Transcortical sensory aphasia - repeating words other people say
Transcode rival motor aphasia - individual can’t produce spontaneous speech
Apraxia speech , known as dyspraxia
Verbal auditory Agnosia- pure word deafness, inability to comprehend
Conduction aphasia- comprehension and spontaneous speech are intact but patient not able to repeat words they have just heard