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Behavioral Neuro > Chapter 13: Lateralization & Language > Flashcards

Chapter 13: Lateralization & Language Flashcards

1
Q

Rasmussen’s Syndrome

A 
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
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2
Q

The Split Brain

A

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
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3
Q

The Split Brain:

Language capacities between two hemispheres

A

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
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4
Q

Left Hemisphere

A

logical, language, sequential; verbal

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5
Q

Right Hemisphere

A

emotional, intuitive; spatial relations

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6
Q

Development of Lateralization

A

Lateralization is not unique to humans.

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

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7
Q

Lateralization: Role of prenatal androgens

A
  • 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
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8
Q

Lateralization Factors

A
  • 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.
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9
Q

Hemispheric Asymmetry:

Left Handers

A

10% left-handed

  • 70% localize language to left hemisphere
  • 15% localize to right hemisphere
  • 15% localize to both hemispheres
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10
Q

Hemispheric Asymmetry:

Right Handers

A

90% right-handed

  • 95% localize language to left hemisphere
  • 4% localize to right hemisphere
  • 1% localize to both hemispheres
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11
Q

Handedness & Language

A

Dioula tribe: 3.4% left-handed.

Yanomamo tribe: 22.6% left handed.

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12
Q

Dichotic Listening

A

different sounds presented simultaneously to both ears.

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

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13
Q

Prosody

A

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.
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14
Q

Hemispheric Asymmetry:

Musical ability

A
  • Imaging results suggest overlap between language and music

- rTMS suggests right hemispheric activity only

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15
Q

Musical ability:

Perfect pitch

A
  • Planum temporale: brain region near auditory cortex.
  • Larger in left hemisphere.
  • Twice as large in musicians with perfect pitch.
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16
Q

Hemispheric Asymmetry:

Gender differences

A
  • 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.
17
Q

What is a language?

A

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
18
Q

Origin of Language

A

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

19
Q

FOXP2 genes

A

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.
20
Q

Schizophrenia

A

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
21
Q

Are Nonhumans Animals Capable of Language?

A

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

22
Q

Bilingualism

A

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.

23
Q

Bilingualism: MRI

A

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

24
Q

American Sign Language

A

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

25
Q

Wernicke’s area

A

Word comprehension

26
Q

Broca’s area

A

Speech response generation

27
Q

Speech production

A

controlled via motor cortex (and Basal Ganglia) activation

28
Q

Contemporary Language Model

A

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

29
Q

Aphasias

A

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.

30
Q

Conduction Aphasia

A 
• 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.

31
Q

Transcortical Aphasias

A

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
32
Q

TC motor aphasia:

A
  • 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
33
Q

Alexia

A

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
34
Q

Agraphia

A
  • Inability to write
  • Damage to motor control areas
  • Phonological agraphia: unable to sound out new or difficult words
  • Orthographic agraphia: can spell only phonetically
35
Q

Reading and Writing

A

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

36
Q

Dyslexia

A

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
37
Q

Dyslexia:

Visual-Perceptual difficulties

A 
–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
38
Q

Stuttering

A

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

Behavioral Neuro (12 decks)

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