Language Disorders Flashcards
language basics
- Comes from word for tongue
- Combination of sound for communication (although ASL is included here too)
- Uniquely human (animals have similar abilities, but not language per say)
7 components of language structure
- Phonemes: fundamental language sounds that form a word
- Morphemes: smallest meaningful units of words
- Lexicon: collection of all words in a given language
- Syntax: rules of grammar; thing that no other species appear to be able to do
- Semantics: meaning of words and sentences that correspond to all lexical items
- Prosody: vocal intonations (“tone of voice”)
- Discourse: stringing sentences together to form a meaningful narrative
language in non-human animals
- Some success with ASL and “Yerkish” in chimpanzees
- Nim Chimpsky experiment – raised like a human in terms of language development, but never learned syntax
- Mothers who learned “Yerkish” passed it down to their babies
- Alex the Parrot showed impressive cognition and comprehension, including generativity
key brain regions in language production
- Broca’s area
- Wernicke’s area
Broca’s area (2 parts, damage)
- damage to it results in ability to understand speech, but cannot produce it (ex. “Tan” - man who could only say Tan after a stroke)
- 2 parts:
- Anterior region involved in semantical processing (meaning of words)
- Posterior region involved in phonetic production
Wernicke’s area (damage)
damage to it results in ability to produce speech, but it’s non-sensical and may reflect lack of comprehension (“word salad”)
anatomical areas associated with language
- Fissures and gyri
- Brodmann’s area
- Insula and medial superior temporal gyrus
- Arcuate fasciculus: white matter bundle travelling from Broca’s area to Wernicke’s area
speech zone mapping with brain imaging techniques
- Through fMRI, Binder et al. Found that speech zones are widespread throughout the brain
- Different areas activated depending on tasks:
- Ex. Thinking about nouns activates 3 different areas
- Hearing overlaps more with Wernicke’s area, speaking overlaps more with Broca’s areas
Wilder Penfield
identified and mapped neocortical language/speech zones during surgery
Effects of cortical stimulation in speech zones
- Total arrest of speech
- Hesitation and slurring of speech
- Speech distortion and repetition of speech
- Number confusion while counting
- Naming difficulties
- Misnaming and perseveration
- These apply to modern stimulation (e.g. TMS)
Wernicke-Geschwind Model
- the old theory
- word sounds sent to Primary Auditory cortex -> meaning represented in Wernicke’s area -> sent to Broca’s area -> Broca’s sends speech articulation to motor cortex
- when reading, visual cortex sends info to angular gyrus and to Wernicke’s or Broca’s area
- Damage to Broca’s area causes issues with production, damage to Wernicke’s area causes issues to comprehension
Shortcomings to the Wernicke-Geschwind Model
- Doesn’t take into account many other brain regions involved
- Overly simplistic when it comes to “regions” of Broca’s area, Wernicke’s area, and directionality of flow
- Relied mostly on diffuse loss-of-function studies
Dual-Language Pathway theory
- contemporary theory
- language moving in multiple directions: bottom-up/dorsal language pathway and top-down/ventral language pathway
- area 6 (motor cortex) and 47 (semantics) often targets of flow of info
Dual-Language Pathway theory: bottom-up/dorsal pathway
- language production
- phonetics
- used when repeating nonsense words
- short-term/working memory
- damage causes problems with speech production
Dual-Language Pathway theory: top-down/ventral processes
- semantics/meaning of language
- separating homonyms
- long-term memory (vocabulary)
- damage causes problems understanding the meaning of words
language disorders
- Aphasia (fluent vs. Non-fluent)
- Alexia (inability to read)
- Dyslexia (difficulty reading)
- Agraphia (inability to write)
fluent aphasia
- impairment in input or reception of language, but not production
- 3 sub-components:
- Wernicke’s/Sensory aphasia
- Conduction aphasia
- Anomic/Amnesic aphasia
Wernicke’s/Sensory Aphasia
- Deficits in classifying sounds or comprehending words
- “Word salad”: intelligible words strung together randomly (patient confuses phonetic characteristics)
- Cannot write because cannot discern phonemic characteristics
conduction aphasia
- Can speak, name objects, and understand speech but cannot repeat words
- Problem is a disconnection between the “perceptual word image” and the motor systems producing the words
Anomic/amnesic aphasia
- Can comprehend speech, produce meaningful speech, and can repeat speech
- Great difficulty naming objects
- Ex. Seeing a picture of an anchor, being able to describe it (ie. “you use it to anchor a ship”), but can’t access it as a noun
non-fluent aphasia (2 types)
- Broca’s/expressive aphasia
- Global aphasia (laboured speech, poor comprehension)
Broca’s/expressive aphasia
- Can understand speech
- Labours hard to produce speech
- Can be mild or severe
fluent and non-fluent aphasia
- Transcortical aphasia, or isolation syndrome
- Can repeat words (echolalia)
- Cannot speak spontaneously
- Often poor comprehension
why is studying neural basis of language (and localizing lesions) complex?
- Most of the brain takes part in language in one way or another
- Most patients who add information to studies of language have had strokes, usually of the middle cerebral artery
- Immediately following stroke, symptoms are generally severe but improve considerably as time passes
- Aphasia syndromes described as nonfluent (Broca’s) or fluent (Wernicke’s) have many varied symptoms, each of which may have different neural basis
cortical language components: non-fluent
usually to Broca’s area, presumably dorsal pathways
cortical language components: fluent
Usually to Wernicke’s area, presumably ventral pathway
Right-hemisphere contributions to language
- Good auditory comprehension of language
Left-hemisphere contributions to language
- syntactical language
- sequencing
- relations
- grammar
symptoms of non-fluent aphasia
- Apraxia of speech: damage to the insula
- Deficits in sentence comprehension: damange to superior temporal gyrus
- Repetition of speech: damage to arcuate fasciculus
- Working memory and articulation impairment: Broca’s area damage
symptoms of fluent aphasia
- Lack of speech comprehension and other core difficulties with language
- Damage to the medial temporal lobe and underlying white matter
- Damage to temporal cortex contributes to deficits in holding sentences in memory until can be repeated
what is aphasia?
- Neurologic disorder that impairs an individual’s ability to use and/ or understand language
- Commonly occurs after stroke to left cerebral hemisphere or other injury to the brain’s language network
- Impairments depend on size of lesion and individual patient differences
Diagnosing & treating aphasia
- Diagnosed using object naming, comprehension, repetition, reading, writing, etc. tasks
- treated using speech-language therapy, medication, or brain stimulation
aphasia treatment: speech-language therapy (SLT)
- Capitalize on preserved abilities, provide compensatory strategies to improve communication (ie. communication boards, online device)
- 3 recovery stages: acute, subacture, chronic
SLT: acute recovery stage
- Up to 3 weeks
- Spontaneous recovery of function due to physiological restitution of damaged brain
SLT: subacture recovery stage
- 3 weeks-12 months
- Spontaneous recovery due to physiological reorganization of the brain
- SLT is effective beginning in this phase
SLT: chronic recovery stage
- More than 12 months
- SLT is still effective in this phase (effective across life course)
- Most positive effects with higher intensity of treatment
aphasia treatment: medication
drugs that enhance neurotransmitter pathways may mitigate the damage done to those pathways due to strokes
aphasia treatment: brain stimulation
- non-invasive electrical stimulation or magnetic pulses
- Effects can last for hours after session and enhance learning during motor or language training
- Either enhance left hemisphere activity, reduce right hemisphere activity, or both
hemispheres and language -> responsibility & removal
- left hemisphere usually more responsible (but in some people, both are)
- If left hemisphere removed early, the right can acquire language (if removed in adulthood, severe deficits in speech but still good auditory comprehension)
- Removal of the right hemisphere produces subtle changes in language comprehension
