Brain and Language lec pt 2

1. The Brain and Language: Aphasias

1.1 Left Lateralization of Language

• Evidence from previous lectures (recalled).

• Broca's Aphasia (1861, Paul Broca)

  • Patient: "Tom" - could only say "Tom" or "Tom, Tom" but understood language.

  • Damage Location: Broca's area, specific area in the brain (post-mortem autopsy).

  • Crucial Contribution: Correlation between specific language deficit and damage to a particular brain area.

  • Symptoms:

    • Speech: Labored and difficult, non-fluent (e.g., "cookie jars falling, rolling, falling off stool. Mom.").

    • Comprehension: Basically intact.

    • Writing: Difficult to read, few words, but generally makes sense (like their speech).

    • Syntactic structure: Severely impaired (rarely complete sentences).

    • Semantics/Meaning: Preserved.

• Wernicke's Aphasia (1874, Carl Wernicke)

  • Discovery: A different language deficit associated with damage to a different brain area (Wernicke's area) in the temporal lobe.

  • Symptoms:

    • Speech: Very fluent, complete grammatical sentences, but doesn't make sense (word choice and meaning problems).

    • Comprehension: Severely impaired; often unclear if the person understood the question.

    • Writing: More words, better handwriting, but the text is nonsensical (e.g., "boy is on chair is on cookie jar is own the boy is on cookie.").

    • Syntactic structure: Preserved.

    • Semantics/Meaning: Severely impaired, difficult to understand speaker's intent.

  • Also called: Semantic aphasia due to issues with meaning.

• Conclusions from Aphasia Studies

  • Damage to specific brain areas correlates with specific linguistic deficits.

  • Language is not housed in a simple box but is localized to specific areas, primarily in the left hemisphere.

  • Symptoms hold in both speech and writing, indicating a brain problem, not just a speech problem.

2. Brain Imaging Techniques: Functional Magnetic Resonance Imaging (fMRI)

2.1 What is fMRI?

• Purpose: Allows observation inside living brains to understand their function.

• Mechanism: Takes a series of pictures to get a dynamic view of brain activity.

  • It's a gigantic magnet ( $30,000$ times stronger than Earth's magnetic field).

  • Measures changes in magnetic properties of oxygenated and deoxygenated blood.

  • More neural activity (neurons firing) leads to increased oxygenated blood, which gives a bigger MRI signal.

  • Indirect measure of brain activity.

2.2 fMRI Experiment Setup

• Alternating periods of rest and task (e.g., listening to sounds, producing speech).

• Measures MRI signal during rest (inactive wave) and during task (active wave).

• Subtracts inactive wave from active wave to determine areas of brain activity during a specific task.

2.3 Application: Sign Languages vs. Spoken Languages

• Hypothesis: If sign languages are full human languages (differ only in modality), they should activate the same brain areas as spoken languages.

• Experiment (English vs. British Sign Language):

  • Subjects: Native hearing English speakers, hearing BSL signers, native deaf BSL signers.

  • Task: Silently reading English sentences or watching BSL sentences.

  • Results: All three groups showed activation in Broca's area (frontal lobe) and Wernicke's area (temporal lobe) in the left hemisphere.

• Conclusion: Despite different modalities, sign languages and spoken languages are processed in the same brain areas, supporting that sign languages are full human languages.

3. Language Abilities and General Intelligence

3.1 Hypothesis

• If language ability is tied to general intelligence:

  • Low IQ should correlate with poor language ability.

  • High/normal IQ should correlate with strong language ability.

3.2 Specific Language Impairment (SLI)

• Prevalence: Affects $7\%$ to $8\%$ of kindergarten children.

• Characteristics: Language problems with specific grammar aspects (e.g., function/grammatical words like "of," "is," "the").

  • Examples: "meow meow chase mice," "show me knife," "it not long one," "he like me" (instead of "does he like me"), "he walk" (instead of "he walks"), "those dog" (instead of "those dogs").

  • IQ: Within typical/normal range.

  • Other cognitive abilities: Perfectly normal (e.g., speech comprehension, hearing).

• Study (Rice and Oetting, 1993): Compared $50$ five-year-old SLI children with $50$ younger non-SLI children ($38$ months mean age) with similar sentence lengths.

  • Findings: SLI children showed significantly lower correct usage of plural endings (SLI: $83\%$ vs. non-SLI: $93\%$) and third person singular -s on verbs (SLI: $36\%$ vs. non-SLI: $54\%$) compared to younger, typically developing children.

• Conclusion: SLI demonstrates a dissociation where normal IQ correlates with poor language ability in specific areas, suggesting language ability is separate from general intelligence.

3.3 Williams Syndrome

• Condition: Result of deletion from one copy of chromosome $7$ (about $20$ contiguous genes); occurs in $1$ in $25,000$ births.

• Characteristics:

  • IQ: Average $55$ (range $40-90$), low general intelligence.

  • Spatial/Motor Skills: Limited (e.g., difficulty tying shoes, cutting with knife, drawing).

  • Personality: Extremely social, friendly, love music (often perfect pitch).

  • Language: High level of vocabulary and grammar, fluent speech, complex sentences.

  • Other: Better than average facial recognition skills, characteristic pixie/elfin-like appearance.

• Examples:

  • Spatial Ability Task: Children with Williams syndrome drew houses and copied models very differently and atypically compared to controls.

  • Verbal Examples: Ability to produce complex sentences (e.g., "I would fly though the air and soar like an airplane and dive through trees like a bird…"), provide detailed narrations and homonyms, and rich descriptions (e.g., of an elephant).

• Conclusion: Williams syndrome presents a dramatic dissociation where strong, intact language abilities correlate with low general intelligence and other significant cognitive deficits.

3.4 Linguistic Savants

• Definition: Individuals with low general intelligence but exceptionally high language abilities.

• Case: Laura

  • Non-verbal IQ: $41-44$ (very low).

  • Deficits: Doesn't understand math, time, numbers; cannot draw or understand spatial relationships.

  • Language: Extensive vocabulary; creates and understands complex sentences (e.g., passives like "The chair was moved," "he was saying that I lost my battery-powered watch that I love").

• Case: Christopher

  • Non-verbal IQ: $60-70$ (low).

  • Deficits: Lives in an institution, cannot care for himself (e.g., button shirt, walk alone), poor memory for places (gets lost easily).

  • Language: Learned and recognizes dozens of languages (e.g., Hindi, Hungarian, Danish, Dutch, Finnish, German, Modern Greek, Italian, Norwegian, Polish, Portuguese, Russian, Spanish, Swedish, Turkish, Welsh); can read upside down/backwards; fluent in multiple languages.

  • Brain Scan: Normal MRI, no peculiarities.

• Conclusion: Laura and Christopher demonstrate profound dissociation between language ability (very high) and general intelligence (very low).

4. Overall Summary of Brain and Language

• Language is Lateralized: Primarily housed in the left hemisphere of the brain.

  • Evidence: Broca's aphasia, Wernicke's aphasia, fMRI techniques, Wada test, dichotic listening.

• Language is Localized: Specific areas like Broca's and Wernicke's areas are identifiable language centers.

• Sign and Spoken Languages: Activate the same brain areas, consistent with both being fully human languages, differing only in modality.

• Language and Intelligence Dissociation: Language ability is not directly tied to general intelligence.

  • Double Dissociation:

    • SLI: Normal IQ with language deficits.

    • Williams Syndrome & Linguistic Savants: Intact (or superior) language abilities with low general intelligence and other cognitive deficits.