Psy 362 Language Disease

NEUROPSYCHOLOGY OF LANGUAGE

Overview of Language and the Brain

  • Introductory Question: What one thing do you know about language and the brain?

Left Hemisphere Dominance for Language

  • Findings: The left hemisphere is predominantly responsible for language processing.

  • Inquiry: How do we know this?

    • Diagnosis Context: Research on patients with epilepsy undergoing surgical removal of brain tissue.

    • Testing Method: These patients are assessed to establish which hemisphere is adept for language processing.

Wada Test

  • Definition: The Wada test is a procedure used to ascertain language hemisphere dominance.

  • Procedure:

    • Anesthetic Use: One side of the brain is anesthetized using a short-acting drug (sodium amytal).

    • Evaluation: Following anesthetic administration, a doctor quickly assesses the patient's language capabilities.

    • Hemisphere Comparison: The anesthetic procedure is repeated for the other hemisphere to gather comparative data.

  • Statistical Outcome:

    • 99% of the population is left hemisphere (LH) dominant for language use.

    • Right-Handed Individuals: Over 99% LH dominance.

    • Left-Handed Individuals: Approximately 90% LH dominance.

Consequences of Left Hemisphere Damage

  • Impact: Damage to various left hemisphere (LH) areas can yield a host of language impairments.

Types of Language Disorders

  • Classification: Language disorders can be categorized into two primary classes:

    • Acquired Language Disorders

    • Developmental Language Disorders

Acquired Language Disorders

  • Aphasia Defined: A primary dysfunction affecting spoken language.

  • Associated Disorders:

    • Aphasia: Challenges with spoken language and expression.

    • Alexia/Dyslexia/Agraphia: Issues related to written language capabilities.

Aphasias

Wernicke's Aphasia

  • Historical Context: Named after Karl Wernicke.

  • Typical Causes: Results from damage specifically to the left temporal-parietal region.

  • Characteristics:

    • Fluent Aphasia: Speech output is grammatically correct but lacks meaning.

    • Comprehension Impact: Significant impairment in understanding spoken words and sentences.

    • Output Characteristics: Fluid speech often lacks coherent content.

    • Neologisms: Frequently includes nonsensical words (e.g., "slunker").

    • Paraphasias: Involves the substitution of words, leading to nonsensical phrases (e.g., "tephelone").

Broca's Aphasia

  • Historical Context: Named after Paul Broca.

  • Typical Causes: Results primarily from damage to the left inferior frontal region.

  • Characteristics:

    • Non-Fluent Aphasia: Language production is severely hampered.

    • Comprehension: Patients may understand simple speech effectively.

    • Production Issues: Speaking becomes laborious and slow, with a significant struggle in forming coherent utterances.

    • Syntax Complexity: Problems manifest with complex sentence structures, particularly with passive constructions.

    • Example Sentences:

      • “Patrick is hugging SpongeBob.”

      • “Patrick is being hugged by SpongeBob.”

Anomic Aphasia

  • Definition: Anomic aphasia relates to issues primarily with retrieving words.

  • Communication Capabilities: Patients retain the ability to speak and understand most language but struggle with finding the correct words.

    • Circumlocutions: Involves discussing surrounding concepts instead of directly naming a desired word.

    • Damage Area: Connected to dysfunction in specific areas of the left temporal-parietal hemisphere.

Written Language Disorders

  • Alexia

    • Definition: A complete inability to read, often stemming from damage to the left angular gyrus.

  • Dyslexia

    • Definition: Refers to impairments in reading functions, associated with diffuse damage affecting the left and right hemispheres.

  • Agraphia

    • Definition: Difficulty in writing, often linked with lesions in the left parietal region.

    • Specific Variant: Alexia without agraphia, where individuals can write but cannot read.

Wernicke-Geschwind Model

  • Model Components:

    • Motor Cortex, Broca's Area, Auditory Cortex, Primary Visual Cortex, Angular Gyrus, Wernicke's Area.

Acquired Dyslexia

Dual Route Model

  • Components: Orthographic, Phonetic, Lexical, Semantic pathways.

    • 1st grade to 4th grade.

      • Learning to read and not reading to learn.

  • Phonological Dyslexia

    • Definition: Characterized by difficulties with the phonological route, requiring reliance on visual recognition.

    • Can’t read aloud unknown words.

  • Surface dyslexia

    • Problem with visual pathway

Right Hemisphere (RH) Language Deficits

  • Prosodic Function:

    • Definition: Refers to the melodic and rhythmic aspects of speech.

    • Effects of RH Damage: Leads to monotonous speech and impairs the ability to use prosody for language comprehension.

    • Example Statement: “We’re having pasta for dinner tonight.”

    • Complications: Includes challenges in grasping humor and metaphorical language, resulting from the loss of intonation and expression, which are crucial for comprehension.