Language Disorders and Aphasias

Comprehensive vocabulary flashcards covering language hierarchy, neuroanatomical models, aphasic syndromes, reading disorders (alexia/dyslexia), writing disorders (agraphia), and numerical cognition (acalculia/dyscalculia).

Phoneme

The smallest unit of sound in a specific language; it does not carry meaning on its own, but serves to distinguish meaning between words.

Morpheme

The smallest meaningful unit of language.

Lexicon

The mental dictionary containing information about words, including their linguistic forms and properties, which is distinct from our entire conceptual knowledge.

Syntax

The rule system that determines how words are ordered and how sentences are structured.

Semantics

The linguistic domain of meaning that connects words and sentences to the external world and internal representations.

Prosody

The stress, intonation, and rhythm of speech that distinguishes statements from questions, conveys irony, and adds emotional nuance.

Discourse

The highest level of language organization consisting of connected sentences, narratives, and coherent storytelling.

Anomia

A word-retrieval deficit in which an individual knows what an object is conceptually but cannot retrieve its spoken name.

Agnosia

The inability to recognize or identify an object despite preserved elementary sensory processing.

Wernicke-Geschwind Model

The classical 19th-century language model proposing three main anatomical components: language comprehension in Wernicke's area, speech production in Broca's area, and a connecting white-matter tract (the arcuate fasciculus).

Broca's Area

An anterior language network region located in the left inferior frontal gyrus (Brodmann areas 44 and 45) responsible for speech motor control, articulation, syntax, phonological processing, and sequential motor planning.

Wernicke's Area

A posterior language network region in the left posterior superior temporal gyrus (Brodmann area 22) responsible for auditory linguistic processing, semantic comprehension, phonological processing, and linking meaning to speech sounds.

Arcuate Fasciculus

The primary white-matter tract connecting Broca's area and Wernicke's area that transmits phonological information and supports verbatim speech repetition.

Dual-Stream Model of Language

A contemporary model dividing speech processing into a dorsal stream (sound-to-articulation for phonology, repetition, and motor production) and a ventral stream (sound-to-meaning for auditory comprehension and semantic processing).

"Brain Dictionary" Hypothesis

The hypothesis proposing that word meanings are distributed across widespread brain networks, where different regions contribute distinct perceptual, motor, and semantic features.

Aphasia

An acquired disorder of communication primarily affecting verbal language across one or more hierarchical components, typically resulting from focal left-hemisphere damage.

Broca's Aphasia

A non-fluent aphasia caused by lesions in the left inferior frontal gyrus, characterized by effortful, slowed speech, agrammatism, impaired repetition, and impaired naming, with relatively preserved comprehension.

Agrammatism

A feature of non-fluent language production marked by the omission or reduced use of grammatical morphemes and difficulty producing or understanding complex grammatical structures.

Wernicke's Aphasia

A fluent aphasia caused by left posterior superior temporal damage, characterized by logorrhoea, severely impaired comprehension, impaired repetition, impaired naming, preserved prosody, and numerous paraphasias.

Paraphasia

The unintended substitution of syllables or words during speech, divided into semantic paraphasia (substituting a semantically related word) and phonemic paraphasia (substituting a phonologically similar word sound).

Jargon Aphasia

An extreme form of fluent aphasic speech characterized by copious phonemic and semantic paraphasias and neologisms, rendering spoken output unintelligible.

Conduction Aphasia

A fluent aphasia caused by disruption of the arcuate fasciculus and surrounding networks, characterized by relatively intact comprehension and naming, fluent speech with phonemic paraphasias, and disproportionately impaired repetition.

Anomic Aphasia

A fluent aphasia linked to parietal or temporal lesions, marked by isolated, prominent word-finding and naming deficits with intact comprehension, repetition, and spontaneous fluency.

Transcortical Motor Aphasia

A non-fluent aphasia resulting from left anterior frontal damage, characterized by non-fluent spontaneous speech and impaired naming, but remarkably preserved repetition and auditory comprehension.

Transcortical Sensory Aphasia

A fluent aphasia linked to posterior temporoparietal lesions, characterized by fluent speech and preserved repetition, alongside severely impaired comprehension and impaired naming.

Global Aphasia

A severe language deficit following extensive dominant-hemisphere damage, causing pervasive impairment across all modalities: non-fluent speech, poor comprehension, poor repetition, and poor naming.

Dual-Route Model of Reading

Morton's cognitive model positing two routes for reading aloud: an indirect phonological route (rule-based grapheme-to-phoneme conversion) and a direct lexical-semantic route (rapid whole-word recognition linking orthography directly to meaning and pronunciation).

Surface Dyslexia

A reading deficit characterized by an inability to read via the direct lexical route, forcing reliance on letter-by-letter grapheme-phoneme conversion and causing severe difficulty reading irregular words.

Phonological Dyslexia

A reading impairment characterized by disrupted phonological decoding of unfamiliar words and pseudowords, while familiar words are read relatively well, often showing lexicalization errors.

Deep Dyslexia

A severe reading disorder marked by impaired phonological decoding and the production of semantic paralexias (e.g., reading "table" aloud when seeing "chair").

Pure Alexia

An acquired reading deficit caused by damage to the orthographic input lexicon (OIL), resulting in impaired whole-word recognition, dissociation between word and letter recognition, and laborious letter-by-letter reading.

Phonological Output Lexicon (POL) Disruption

An alexic disorder where reading aloud is severely impaired despite intact reading comprehension, often producing semantic errors with preserved patient awareness of the mistakes.

Semantic Paralexia

An error during reading in which a written word is misread as a semantically related item (e.g., "cat" read as "dog") due to faulty access to specific semantic categories.

Lexical (Surface) Agraphia

A writing disorder caused by impaired mapping from lexical semantics to orthography, forcing dependence on grapheme-phoneme rules and producing errors on irregular words.

Graphemic Buffer Agraphia

A writing disorder caused by impaired working memory retention of letter sequences, where spelling errors increase progressively with word length.

Apraxic Agraphia

A writing impairment characterized by the inability to plan and execute the motor programs required for writing, resulting in distorted and effortful letter formation.

Allographic Impairment

A writing deficit specifically involving difficulty selecting the correct visual/case form of a letter (e.g., uppercase vs. lowercase).

Three-Code Model of Numerical Processing

Dehaene's neurocognitive model stating that numbers are processed across three distinct representations: visual number form, verbal number representation, and analog magnitude representation.

Analog Magnitude Representation

A non-symbolic numerical representation of quantity along a mental number line that links visual forms and verbal codes, supported bilaterally by parieto-occipito-temporal cortex.

Visual Number Form

The visual format used to represent numbers as symbols (such as Arabic numerals), exhibiting left occipitotemporal dominance.

Verbal Number Representation

The language-based format for number words and arithmetic operations, specialized for the storage and retrieval of rote arithmetic facts (such as multiplication tables) in the left hemisphere.

Number Syntax Errors

Acalculic errors involving difficulty interpreting and manipulating the place-value and grammatical structure of multi-digit numbers.

Procedural Impairment (Acalculia)

An acalculia subtype following inferior parietal damage where arithmetic facts and basic number rules remain preserved, but the sequential execution of specific multi-step mathematical operations is impaired.