Chapter 13: Lateralization & Language

Question 1

Rasmussen’s Syndrome

Answer 1

produces seizure in only one hemisphere
Hemispherectomy:
-Motor control modestly impaired
-Language development mostly unaffected
-10 point increase in IQ
-Recovery of function correlates with age of surgery

Question 2

The Split Brain

Answer 2

Pathways connecting two hemispheres severed in order to control seizures.

Corpus collosum, Massa intermedia, Thalamus, Anterior commisure and Hippocapmus pathways are disrupted

• No change in personality, intelligence, or speech
• Two separate minds
• Alien hand syndrome

Question 3

The Split Brain:

Language capacities between two hemispheres

Answer 3

The Interpreter: one hemisphere (usually left) tries to make sense of actions

• Right hemisphere may point to object, but left hemisphere does not know why
• Interpreter attempts to generate a reasonable explanation

Question 4

Left Hemisphere

Answer 4

logical, language, sequential; verbal

Question 5

Right Hemisphere

Answer 5

emotional, intuitive; spatial relations

Question 6

Development of Lateralization

Answer 6

Lateralization is not unique to humans.

May allow organisms to simultaneously attend to different aspects of environment.

Question 7

Lateralization: Role of prenatal androgens

Answer 7

• Males: higher proportion of left-handers
• Congenital adrenal hyperplasia (CAH): fetus’ adrenal glands release elevated levels of androgens
• Females exposed to twice normal level: no difference in handedness or language laterality
• Males exposed to slightly elevated levels: higher proportion left-handed but no difference in language

Question 8

Lateralization Factors

Answer 8

• Genes responsible for connectivity between two hemispheres activated at 3-5 months.
• Differential gene expression might result in different wiring patterns, leading to structural and functional differences later in life.

Question 9

Hemispheric Asymmetry:

Left Handers

Answer 9

10% left-handed

• 70% localize language to left hemisphere
• 15% localize to right hemisphere
• 15% localize to both hemispheres

Question 10

Hemispheric Asymmetry:

Right Handers

Answer 10

90% right-handed

• 95% localize language to left hemisphere
• 4% localize to right hemisphere
• 1% localize to both hemispheres

Question 11

Handedness & Language

Answer 11

Dioula tribe: 3.4% left-handed.

Yanomamo tribe: 22.6% left handed.

Question 12

Dichotic Listening

Answer 12

different sounds presented simultaneously to both ears.

Right handers typically show right ear (left hemisphere) advantage.

Question 13

Prosody

Answer 13

Prosody = use of intonation and stress in language to convey emotional tone and meaning.

• Left ear, right hemisphere advantage in responding to emotional words.
• Orbitofrontal cortices in both hemispheres respond to conscious evaluation of emotional tone.

Question 14

Hemispheric Asymmetry:

Musical ability

Answer 14

• Imaging results suggest overlap between language and music

- rTMS suggests right hemispheric activity only

Question 15

Musical ability:

Perfect pitch

Answer 15

• Planum temporale: brain region near auditory cortex.
• Larger in left hemisphere.
• Twice as large in musicians with perfect pitch.

Question 16

Hemispheric Asymmetry:

Gender differences

Answer 16

• 3-7 times many boys than girls diagnosed with language disorder.
• Girls begin speaking at younger age, have larger vocabulary, and better reading skills.
• Large meta-analysis found gender difference in lateralization of handedness but not language.

Question 17

What is a language?

Answer 17

System of rule-based communication that combines symbols (sounds and gestures) in order to express a meaning, idea, or thought.

–Transmit info
–Express thoughts and emotions
–Automatic, complex, and coordinated
–Use of vocalization to communicate
–No connection between symbol and what it signifies
–Passed from generation to generation
–Communication follows social rules
–Can communicate about objects and events that are distant in time and place

Question 18

Origin of Language

Answer 18

Chomsky & Pinker argue for innate ability to learn language.
No specific instruction needed to learn language, suggestive of language module.
Williams syndrome

FOXP2 genes located on chromosome 7
-Modern language acquired 100-400,000 ya due to specific mutation

Question 19

FOXP2 genes

Answer 19

genes located on chromosome 7.

• KE family: FOXP2 mutation associated with disrupted speech production and comprehension.
• Gene codes transcription factor, which regulates expression of large number of genes.
• Areas in blue functionally or structurally abnormal in KE family.

Question 20

Schizophrenia

Answer 20

Many symptoms are associated with interpretation and organization of language.

• Generally show no hemispheric asymmetry for language or instead mirror asymmetry, with language lateralized to right hemisphere
• Mixed or ambiguous handedness
• 1% of population throughout world, yet patients have low reproduction rate—must be linked to some positive attribute

Question 21

Are Nonhumans Animals Capable of Language?

Answer 21

–Communication not the same as language
–Research with great apes
–Mirror neurons
–Broca’s area

Question 22

Bilingualism

Answer 22

Distinguishing speech sounds: most languages contain 25-40 speech sounds.
Infants younger than ~8 months can distinguish all speech sounds, even those not heard in native language
- /l/ and /r/ differentiated in English but not Japanese
By 11 months, infants can discriminate speech sounds from own language only—supporting idea of critical periods.

Question 23

Bilingualism: MRI

Answer 23

MRI: second language learning increases grey matter density in certain cortical regions
- Density increases correlate with language proficiency

Question 24

American Sign Language

Answer 24

Similar language sites activated for spoken written English as ASL; spoken word activation more lateralized.

Question 25

Wernicke’s area

Answer 25

Word comprehension

Question 26

Broca’s area

Answer 26

Speech response generation

Question 27

Speech production

Answer 27

controlled via motor cortex (and Basal Ganglia) activation

Question 28

Contemporary Language Model

Answer 28

3 interacting language components Language Implementation System: decodes incoming verbal info and produces appropriate verbal responses—depends on Broca’s area, Wernicke’s area, insular cortex, and basal ganglia Mediational System: manages communication between implementation and conceptual systems—depends on the temporal, parietal, and frontal lobes. Conceptual System: manages semantic knowledge—depends on high-level cortical association areas

Question 29

Aphasias

Answer 29

Brain damage that results in total or partial loss of ability to either produce or comprehend spoken language. Brain of Dr. Broca’s patient had damage to left inferior frontal region. While alive, this patient could say only “tan” when questioned.

Question 30

Conduction Aphasia

Answer 30

``` • Damage to Arcuate Fasciculus (pathway from Wernicke’s to Broca’s) • Intact comprehension • Can produce fluent speech but often makes errors (can’t correct them) • Problems repeating speech ``` Conduction aphasia, also called associative aphasia, is a relatively rare form of aphasia. An acquired language disorder, it is characterized by intact auditory comprehension, fluent (yet paraphasic) speech production, but poor speech repetition.

Question 31

Transcortical Aphasias

Answer 31

TC motor aphasia: - Dorsolateral PFC damage - Affects higher cognitive and attentional functions related to language production - Initiation of speech disrupted - Unable to produce verbs related to particular nouns TC sensory aphasia: - Supplementary motor cortex damage - Affects ability to understand meaning of words - Speech is grammatical and fluent

Question 32

TC motor aphasia:

Answer 32

- Dorsolateral PFC damage - Affects higher cognitive and attentional functions related to language production - Initiation of speech disrupted - Unable to produce verbs related to particular nouns

Question 33

Alexia

Answer 33

acquired inability to see words or to read, caused by a defect of the brain. - Word blindness - Can recognize spoken words - Left occipital cortex damage affects ability to perceive words and word-like shapes - Corpus callosum damage prevents transfer of info from right visual cortex to left language areas

Question 34

Agraphia

Answer 34

- Inability to write - Damage to motor control areas - Phonological agraphia: unable to sound out new or difficult words - Orthographic agraphia: can spell only phonetically

Question 35

Reading and Writing

Answer 35

Appeared 5-6000 years ago Usually localized to same hemisphere as speech

Question 36

Dyslexia

Answer 36

Dyslexia: Impairment in reading despite normal intelligence and exposure –10-30% of population –High heritability: 40% chance sibling is also dyslexic –Impaired phonological awareness: ability to discriminate verbal information at level of speech sounds –Difficulty discriminating rapidly presented stimuli ``` Visual-Perceptual difficulties: –Reading a word backwards •“net” becomes “ten” –Confusing mirror image letters •“b” becomes “d” –Trouble fixating on printed words •Words appear to move around page ```

Question 37

Dyslexia: | Visual-Perceptual difficulties

Answer 37

``` –Reading a word backwards •“net” becomes “ten” –Confusing mirror image letters •“b” becomes “d” –Trouble fixating on printed words •Words appear to move around page ```

Question 38

Stuttering

Answer 38

Producing repetitions or prolonging of sounds. –Primarily genetic in origin –Both hemispheres vie to control speech production –Treatments: •Reducing rates at which speech is produced and stress associated with the disorder •Learning special breathing techniques, soft voice onsets, and prolongation of syllables •Dopamine antagonists