L6: Language

Aphasia

loss of language processing ability after brain damage

principles of aphasia

localisation of language processors, damage to single processor can = multiple deficits, language processes are localised due to relationship with primary sensory/motor functions

Broca’s aphasia

non-fluent, expressive aphasia

disturbed speech production

loss of pronouns, telegraphic speech

left frontal lobe (Broca’s area)

Leborgne

Wernicke’s aphasia

fluent, receptive aphasia

disturbed speech comprehension

semantic paraphasias

left temporal lobe (Wernicke’s area)

Conduction aphasia

damaged arcuate fasciculus connecting Broca’s+Wernicke’s areas

failure to repeat, phonemic paraphasias

disconnection syndrome

Wernicke-Lichtheim-Geschwind suggests

angular gyrus for silent reading

Lieschl’s gyrus for silent listening

Agrammatic Aphasia

production and comprehension impaired

dissociable aphasia

Transcortical sensory aphasia

disconnection of auditory and concept centres (TPO junction)

disturbed auditory comprehension, semantic paraphasias

fluent grammatical speech, good repetition

transcortical motor aphasia

disconnection of concept centre from motor and auditory language centres

adynamic speech

intact comprehension and good repetition

phonemes

smallest unit of sound

allophones

different pronunciations of same phoneme

phonetics

how phonemes are produced in different ways

Phonology

sounds composing language and rules governing combination

Semantics

words and meaning

Syntax

grammar

Psycholinguistics

word meaning is separate from the word’s lexical form (sound/spelling)

double disassociation - retrieval can be impared while meaning is intact

tip of tongue effect/anomic deficits

anterior lesions

normally impact syntax

posterior lesions

normally impact semantics

Dysarthia

disturbed speech musculature, ALS/Lou Gehrig’s

poor speech, strength, tone, range of motion

Apraxia

articulatory errors

impaired ability to programme speech

dysarthia and apraxia are both

articulatory motor disorders

Alexia

impaired reading ability

surface, phonological, deep

Dual routes to reading

Phonological route, direct route

Phonological route

grapheme to phoneme conversion

letter strings to sounds

Direct

printed words to meaning, visual form system

Surface alexia

damaged direct route, difficulties with irregular words

Phonological alexia

damaged phonological route, difficulties with new words

Deep alexia

damaged both routes

Agraphia

impaired writing ability

cortical dysgraphia, peripheral, progressive

cortical dysgraphia

can’t access information from lexical stores, or apply phonological rules

peripheral dysgraphia

distortions in motor programs

Hub and Spoke Model - representations of word meaning

meaning is represented by spokes (different sensory and motor systems)

ATL combines everything - semantic hub

Grounded models of word meaning

word meanings are represented in same sensory/motor areas

Hebbian association - representations of word meaning

neurons which fire together wire together

Mirror neurons - representations of word meaning

fire when performing/observing action

Ventral and dorsal language pathways

dorsal - sound processing

ventral - semantics

speech production requires

domain general system

ensure contextually appropriate speech

domain general system

anterior cingulate cortex monitors conflict

frontal cortex resolves

using attention + executive control systems

Speech perception

automatic, requires domain general system in some situations

doesn’t require conscious awareness