Language and Language Disorders

Phonetics and Phonology

  • Phonology: System of sounds within a language.
  • Speech segmentation: Slicing a continuous sound stream.
  • Sound production involves lips, teeth, tongue, and vocal folds.
  • Vowel sounds are modified by the movement of lips and tongue.
  • Features of phoneme production:
    • Voicing.
    • Place of articulation: Where constriction occurs.
    • Manner of production: How airflow is restricted.
  • Fricatives have some airflow restriction; stops have complete blockage.

Word Recognition

  • Sub-lexical processing: Processing parts of words (phonemes, morphemes).
  • Lexical processing: Processing the entire word.
  • Holistic word recognition.
  • Word Superiority Effect: Real words are recognized faster than random letter strings.
  • Typoglycemia Effect: Words remain readable even when inner letters are scrambled if the first and last letters are correct.
  • Lexical Decision Task: Deciding if an item is a real word or non-word.
  • Semantic information is represented in networks.
  • Priming effect: Activation of a word's meaning spreads in the brain's network.
  • Eye movements in reading do not fixate on individual words.
  • Segmental Speech Sound processing (sub-lexical route): Sounding out words by breaking them into smaller phonetic units.
  • Misheard Lyrics: Brain incorrectly processes individual phonemes.
  • Whole-word phonological processing (Lexical Route): Fast recognition of common words.

Brain Areas and Language

  • Broca's area: Motor center for language production.
  • Wernicke's area: Auditory center for language comprehension.
  • Conceptual Center: Semantic meaning; not localized.
  • Lichtheim's Model (House Model): Auditory center connects to concept center to motor production area

Aphasia Types

  • Broca's Aphasia: Impaired speech production; comprehension intact.
  • Wernicke's Aphasia: Impaired comprehension; fluent speech.
  • Conduction Aphasia: Impaired repetition.
  • Transcortical Motor Aphasia: Preserved comprehension and repetition; impaired speech.
  • Isolation Aphasia: Preserved repetition; poor comprehension and speech.
  • Pure Word Deafness: Impaired comprehension and repetition.
  • Transcortical Sensory Aphasia: Impaired comprehension; preserved repetition.
  • Anomic Aphasia: Impaired word finding.
  • Dysarthria: Impaired speech due to motor difficulties.

Components of Language Knowledge

  • Lexical knowledge: Meaning of words.
  • Syntax: Sentence structure (subject-verb-object).
  • Contextual knowledge: Resolving ambiguity.
  • Phonological form: How to produce sounds.

Language Development

  • Early milestones:
    • Birth-3 months: Baby recognizes voices.
    • 4-7 months: Babbling stage.
    • 8 months-1 year: Understands common words.
    • 1 year: Starts talking.
  • Phonemes: Short, distinctive sound units.
  • Morphemes: Smallest units that carry meaning (free and bound).
  • Words: Smallest unit of lexical information.
  • Words are symbols and often arbitrary.
  • Content & Function words.
  • Sentences: Sequences of words constructed with morphemes.

Language Disorders

  • Developmental Language Disorder (DLD):
    • Impairment in age-normed language production or comprehension (not due to low cognitive function, hearing loss, or neurological damage).
    • Prevalence rate of 7% in children.
    • Symptoms: Limited use of complex sentences, difficulty finding words, phonetic challenges, disorganized storytelling.
  • DLD is not caused by acquired brain damage, a learning disability, and is not specific to a particular language.
    • Core symptoms related to syntax, morphology, and phonology.
  • Language trajectories in DLD:
    • Early Start-Up Period: Children with DLD can be delayed by 1 or 2 years.
    • Rapid-growth period: Similar rate of language development in DLD.
    • Plateauing Period: Children with DLD do not "catch up".

Core Language Cortical Regions

  • Broca's Area: Language production.
  • Wernicke's Area: Language comprehension.
  • Arcuate Fasciculus: Connects Broca's and Wernicke's areas.
  • Procedural Memory: Supports rule-based actions; grammar.
  • Procedural Deficit Hypothesis: DLD stems from abnormalities in the procedural memory system.