Language & Language Disorders Flashcards
Inferior frontal gyrus (IFG)
- Broca’s area
- Area 44 and 45
- Production of language
Other regions for speech productions
• The anterior Insula (Left)
- Critical for coordination of speech articulation
- Part of the orofacial motor system
• Precental region: Orofacial musculature control
• The Basal ganglia: cognitive control (enhancement and suppression, initiation)
- support selection of appropriate phonological and
articulatory representations of lexical items
• Cerebellum: motor planing and control
Pendfield and stimulation
• Stimulating Precentral areas: evokes sounds or vocalisation
• Stimulating area 44: speech arrest
• Noted that electrical stimulation in any of
the core language areas of the brain will
affect speech
• Peri-Sylvian areas
Area 45
• Pars Triangularis
• Involved in active retreival of information before it can
be articulated
• Strong connection with auditory, semantics processing
temporal areas
• Strong connections with other frontal areas
→Integration and selective retreival of information
Area 44
• Pars Opercularis
• Intermediate between cognitive retreival (area 45) and
motor/articularoty area (area 6)
• Translate the retreived information into action
• Strong connections to the Supramarginal gyrus
(phonological processing)
Posterior temporal regions (Wernicke)
• Wernicke: the critical region for auditory
language comprehension
→ the superior temporal gyrus
Comprehension of language: Acoustic-phonological analysis of the speech input
• Heschl’s gyrus, Primary auditory cortex (area 41, 42)
→ superior surface of the temporal lobe
→ processing of any type of sound
• Superior temporal gyrus (STG) and sulcus (STS) (area 22), Secondary auditory cortex
→ responds to acoustic features of phonetic parameters
→ differentiate speech versus nonspeech sounds
Comprehension of language: Syntactic and semantic processing
MTG: comprehension of words STG : • pSTG/STS -semantics, grammatical aspects • aSTG - processing syntactic structure (ex: not activated when just a list of words), but also for semantic processing
Sentence processing
1) acoustic-phonological analysis
2) sentence-level processing: local phrase is built on the
basis of word categories
3) syntactic and semantic relations in the sentence =
interpretation and comprehension
Connections within the language network
• Short range (e.g.: within the IFG) and long range (e.g.: connecting temporal to frontal language areas) • Dual stream model - the ventral pathway: →support sound-to-meaning mapping, - the dorsal pathway: → support auditory-motor integration
Arcuate Fasciculus (AF)
• The classic language pathway
• A large bundle of axons that link the posterior temporal language region with ventrolateral frontal areas arching around the posterior end of the lateral fissure.
• The AF connects the posterior temporal region involved in the comprehension of language (often referred to as Wernicke’s area) with the inferior frontal gyrus (IFG) where Broca’s area lies, i.e. the key region for language production
• Lesions of the fibers of the left AF disconnecting the
posterior temporal language region from the IFG are
considered to result in conduction aphasia
Impairment in the repetition of speech
Two branches of the AF
• Ventral branch: Connecting the IFG
• Dorsal branch: Connecting more dorsal regions of the frontal lobe (ex: area 8), for attentional control
→auditory frontal attention
The Superior Longitudinal Fasciculus (SLF)
3 Major branches:
SLF I: links the superior parietal lobule with caudal dorsolateral and dorsomedial frontal regions
SLF II: links the caudal part of the IPL (Angular gyrus) with lateral frontal areas, including area 45
SLF III: links the rostral part of the IPL (Supramarginal gyrus) with lateral frontal areas (including area 6 ventral and 44)
SLF III
• Stronger connections to area 44
- precise macaque monkey invasive anatomical studies
- resting-state in humans
• Connections of the Supramarginal gyrus with Broca creates an articulatory loop
• Involved in phonological processing
SLF II
- Stronger connections with area 45
- Connections with the Angular gyrus: semantic processing and reading
- Involved in semantic processing and with verbal retrieval.
The Temporo-Frontal Extreme Capsule Fasciculus
- Connects the ventrolateral frontal region with the intermediate part of the supero-lateral temporal region: associated with the long-term storage of semantic information
- Runs under the insula
- Ventral stream of language
- Associated with the controlled retrieval and selection among competing semantic representations
Dorsal and ventral streams
• Superior temporal and premotor regions, activated during repetition, interact via a dorsal pathway along the AF/SLF.
• Middle and inferior temporal regions and the ventrolateral prefrontal cortex, activated during auditory
comprehension, interact via a ventral pathway that runs through the TFexcF
Aphasias
• Disorders of language resulting from brain damage
• Historically, 2 types: language and speech disorders
- Speech: verbal output is impaired, because
articulation muscles are weak or uncoordinated
- Language: verbal output is incorrect linguistically
• Can also observe deficits in comprehension of spoken
or written language (normal hearing and vision)
• Other intellectual abilities are normal
Broca’s aphasia
• Expressive aphasia
• Reduced speech production
• Slow speech, effortful, not fluent
• Poor articulation
• Fails to produce correct English sentences
- Only basic words and endings are omitted
- Aggrammation: no grammatical structure, problems with syntax
• Similar deficits when writing
Preserved:
- Single word finding
- Language (spoken and written) comprehension
- Musical capacities
*Sometimes paralysis of the right side of the body
Wernicke’s aphasia
• Receptive aphasia
• No paralysis
• Speech output speed unaffected or more rapid than normal
• Effortless speech
• Normal prosody, rhythm, melody of speech
• Speech is empty, conveys little information, neologisms
• Paraphasia
• Profound failure to understand language (spoken or written)
-no vision or hearing impairment
• Lost the semantic meaning of words, i.e. the sound patterns received in the primary auditory area
Paraphasia
error in word usage
- phonemic paraphasia: replace a single sound.. Ex: ‘’spoot’’ instead of ‘’spoon’’
- Verbal paraphasia: replace a whole word. Ex: ‘’fork’’ instead of ‘’spoon’’
Wernicke’s theory
• Broca’s area
- located in front of motor areas for face,
tongue, lips, vocal cords…
- Contains the rules and code for articulation
• Wernicke’s area
- Located next to the hearing area
- Involved in the recognition of the patterns of
spoken language
• The two areas must be connected
Conduction Aphasia
• Fluent paraphasiac speech and writing
• Comprehension intact
• Deficits in sentence repetition
→ disconnection between Wernicke and Broca
→ damage to the Arcuate fasciculus
• But each region is intact (fluent speech and normal comprehension)
• Lesions in the inferior parietal lobe near the supramarginal gyrus
- If you ask them a question they will respond so there is some speech comprehension
- If you ask to repeat a sentence: can do it but not exact and harder with difficult sentences
Parietal lesion (around the supramarginal gyrus)
speech is not perfect:
paraphasias, language comprehension problem, concluded that paraphasias (ex : substituting one word for another) is a problem of disconnection
Damage to the anterior and intermediate temporal areas
sound-to-meaning problems, difficulties with semantic interpretation of what is being said
Julia’s Case
- Can’t name things she sees, but she can describe them, she knows what they are.
- Parietal lobe! → translating visual information into speech
Apraxia of speech
• Impairments in the coordination and planning of
speech movements, articulation
• Making articulatory errors
• Intact: ability to perceive speech sounds
• Lesion in the Insula: the left precentral gyrus part
Isolation of the speech area
• No language comprehension • No spontaneous speech production • Can repeat perfectly • Can even complete a sentence →Peri-sylvian language areas are spared but disconnected from the rest of the brain
Lesions in the right hemisphere
Problems :
-prosody, or cadence and intonation of speech, and pragmatics,
-sound flat in their intonation,
-may fail to comprehend emotional nuances, irony, sarcasm, and humor in the speech of others.
→They understand what is said but not how it is said.
• Right hemisphere: music perception
Lateralization of language functions
Language: Left hemisphere Bilateral Right hemisphere
Right-handed 96 % 0 % 4 %
Left-handed 70 % 15 % 15 %
Dyslexia
• Difficulties in the acquisition of literacy
• Can show some impairments in speech processing on tasks requiring manipulation and memory of speech sounds
• Also some low-level visual processing (ex: fast moving objects)
• Developmental dyslexia can be due to different reason
- less activation in Area 44/6 (articulation) and in ventral occipito-temporal areas
Reading acquisition
- When we learn how to read, we transform some of the visual structures into a specialised area for reading
- Temporal lobe: for sentence comprehension, not specialised for reading, also activated when hearing sentences
Alexia with Agraphia
- Patient lost the ability to read and write
- Good vision
- No Aphasia
- Lesion: Angular gyrus
Pure Alexia without Agraphia
One patient:
• right visual field defect
• lost ability to read
• Can still write but can’t read what he just wrote
Lesion: left visual cortex + posterior portion of the corpus callosum
Dejerine’s explanation: written language can only reach the right hemisphere (and no transfer possible to the left-language comprehension hemisphere)
Seeing language
Retina → Striate cortex → Secondary visual areas → Angular gyrus (where visual information is represented in space)
Hearing language
Ears → Primary auditory area → Wernicke’s area
Lesions of the VWFA
Also causes Pure Alexia
This part of the cortex possesses prior properties making it appropriate for reading
• Preference for high-resolution shapes
• Sensitivity for line configurations (useful for object recognition)
• Location: Proximity and connections to spoken language areas
The recycling hypothesis
As you acquire expertise, the VWFA area of the fusiform area becomes more active
Dysgraphia
• Developmental dysgraphia
→Impairment in acquisition of writing skills
- Handwriting impairement
- Can also affect spelling
Agraphia
Acquired writing impairment : lesion
Two sources:
1) Don’t know or remember how to write the words:
-phonological aspect, orthographic memory
2) Can’t write: motor aspect → apraxic dysgraphia
