language and literacy

Language

A system for linking expression to meaning, made up for a finite set of elements (sound, grammar rules) which can be combined in finitely many ways to generate meaning.

Phoneme

The smallest unit of sound that conveys information.

Morpheme

The smallest meaningful representational unit in a language.

Syntax

The arrangement of words into sentences.

Semantics

The meaning of words/phrases/sentences.

Mental lexicon

A mental store of information about words for speech, including semantic information, syntactic information, sound patterns, and spelling patterns.

Aphasias

Language disorders that affect speech production and comprehension.

Broca's Aphasia

Difficulty in speech production, halting speech production without function words, and difficulty comprehending sentences where syntax is crucial to understanding.

What happens if we lesion Broca's area (Inferior frontal gyrus in left hemisphere)?

Speech production is affected.

Wernicke's Aphasia

Produces very fluid sentences, but they don't make sense. Impairment in comprehending words and sentences that are spoken to them.

What happens if we lesion Wernicke's area (Superior temporal gyrus in left hemisphere)?

Speech comprehension is affected.

Double dissociation of Broca's Aphasia and Wernicke's Aphasia

Patients with Broca's aphasia show impairment in both speech production and comprehension, while patients with Wernicke's aphasia produce fluent but nonsensical speech and have comprehension impairments.

Dual Stream Model of Speech Processing

A model by Hickok & Poeppel where early speech processing occurs bilaterally, and the Words Areas are mostly left-lateralized.

Dorsal Stream

Maps sounds onto articulatory motor representations (how to say that word).

Ventral Stream

Maps sounds onto lexical conceptual representations (what that word means).

N400

Negative potential, semantic processing, relative to baseline (positive is negative), elicited when an unexpected incongruent word is encountered.

What is N400 dependent on?

Both word knowledge and world knowledge and makes judgment of contextual fit and anticipation of conceptual features of upcoming words (Coffee fits better than Dog).

Literacy

The ability to read and write. Is correlated with the visual word form area.

Grapheme

Smallest meaningful unit of written language.

Word superiority effect

Reaction time for detecting letters is shorter when they are in a real word or non-word that follows a real word compared to isolated letters.

Visual word recognition

The process of identifying written words and letters. BOLD signal is unaffected by length of real words

Visual word form area

An expert system in the left fusiform gyrus for recognizing written language, responding more to common letter patterns than to consonant strings.

Pseudo-letters

Does not respond to. Fake letters/fonts or shapes that look like letters.

Dual route model of reading: Lexical-Semantic Route

Access semantics directly, faster, and more efficiently for common words. Read words that you know, and not ones that you don't know (as long as we've seen them and know them).

Dual route model of reading: Grapheme-Phoneme Conversion Route

Uses known regularities between spelling patterns and phonological patterns (e.g., "th"). Can accurately read non-words and regularly spelled words.

Dyslexia

A reading disorder that can be acquired (lesion/brain injury) or developmental (genetic risk factors in childhood).

Developmental dyslexia (DD)

Characterized by lower activation of the visual word form area.