Chapter 16 -Lateralization, Language, and the Split Brain

Question 1

Broca’s discoveries

Answer 1

–Aphasia

– Inferior left prefrontal lobe

Question 2

Liepmann

Answer 2

–Apraxia

Question 3

Broca’s Area

Answer 3

The location of Broca’s area: in the inferior left prefrontal cortex, just anterior to the face area of the left primary motor cortex.

Question 4

Aphasia

Answer 4

brain damage–produced deficit in the ability to produce or comprehend language.

Question 5

apraxia

Answer 5

is almost always associated with left-hemisphere damage, despite the fact that its symptoms are bilateral (involving both sides of the body). Patients with apraxia have difficulty performing movements when asked to perform them out of context, even though they often have no difficulty performing the same movements when they are not thinking about doing so

Question 6

cerebral dominance

Answer 6

According to this theory, one hemisphere—usually the left—assumes the dominant role in the control of all complex behavioral and cognitive processes, and the other plays only a minor role. This thinking led to the practice of referring to the left hemisphere as the dominant hemisphere and the right hemisphere as the minor hemisphere.

Question 7

sodium amytal test is a

Answer 7

test of language lateralization (Wada, 1949) is often given to patients prior to neurosurgery

Question 8

sodium amytal test involves

Answer 8

the injection of a small amount of sodium amytal into the carotid artery on one side of the neck. The injection anesthetizes the hemisphere on that side for a few minutes, thus allowing the capacities of the other hemisphere to be assessed. During the test, the patient is asked to recite well-known series (e.g., letters of the alphabet, days of the week, months of the year) and to name pictures of common objects. Then, an injection is administered to the other side, and the test is repeated.

Question 9

dichotic listening test is

Answer 9

noninvasive; thus, it can be administered to healthy individuals.

Question 10

Tests of Cerebral Lateralization

Answer 10

Sodium amytal test •Dichotic listening test •Functional brain imaging

Question 11

Brain damage data

Answer 11

60% dextrals have aphasia –30% sinestrals left handers

Question 12

left hemisphere is dominant

Answer 12

for language-related abilities in almost all dextrals and in the majority of sinestrals.

Question 13

Discovery of the Relation Between Speech Laterality and Handedness

Answer 13

About 92% right-handed subjects are left-hemisphere
dominant for speech
–About 69% of left-handed and ambidextrous are left-hemisphere dominant for speech
–Early left-hemisphere damage may cause right-hemisphere dominance for speech

Question 14

Sex Differences in Brain Lateralization

Answer 14

male victims of unilateral strokes were three times more likely to suffer from aphasia than female victims

Question 15

Myers and Sperry Experiment

Answer 15

• Help to define the role of the corpus callosum

- 1953 by an experiment on cats

Question 16

Myers and Sperry Experiment - conclusions

Answer 16

Forebrains are independent for learning and memory
▪ Corpus callosum carries information between hemispheres
▪ Best study method is to limit information to a single hemisphere

Question 17

Commissurotomy in Humans with Epilepsy - Procedure to test hemispheric independence

Answer 17

Visual stimuli flashed to left or right fixation point –Tactual information presented to “blind” hand –Require verbal or manual response

Question 18

Commissurotomy in Humans with Epilepsy - conclusions

Answer 18

Confirm independent streams of consciousness –Left hemisphere could speak, right could not

Question 19

Vogel and Bogen,

Answer 19

to initiate a program of commissurotomy for the treatment of severe intractable cases of epilepsy—despite the fact that a previous similar attempt had failed, presumably because of incomplete transections

Question 20

The therapeutic benefits of commissurotomy turned out

Answer 20

to be even greater than anticipated: Despite the fact that commissurotomy is performed in only the most severe cases, many commissurotomized patients do not experience another major convulsion.

Question 21

Evidence That the Hemispheres of Split-Brain Patients Can Function Independently - left

Answer 21

Object presented to left hemisphere
–By touching with right hand or viewing in right visual field ▪ Subject could pick out the correct object with right hand
▪ Could name correct object
▪ Could not pick out the correct object with left hand

Question 22

Evidence That the Hemispheres of Split-Brain Patients Can Function Independently - right

Answer 22

Object presented to right hemisphere
–By touching with left hand or viewing in left visual field ▪ Subject could pick out the correct object with left hand
▪ Claimed nothing had been presented
▪ Could not pick out the correct object with the right hand

Question 23

Cross-Cuing

Answer 23

Communication across hemispheres by a non- neural route

Question 24

The “Helping-hand” phenomenon

Answer 24

A subject observes their own Left hand pointing to an object (in response to what was seen by the Rt. Hemisphere) & changes/guides the movement with their Rt. Hand so that it points to (or agrees with) what was seen by the Left Hemisphere.

Question 25

Doing Two Things at Once

Answer 25

Helping-hand phenomenon
• Split-brain patients can learn two things at once • Example
• Helping-hand phenomenon
• Visual completion
• Chimeric figures test