Language in the brain Flashcards
What is language?
intention to communicate
symbol usage
ability to articulate something new
Grammar
ability to represent real world situations
What did Rumbaugh (1977) say about language?
“an infinitely open system of communication”
What are the two behaviours of language?
Language production - from thoughts to mouth and tongue movement
Language comprehension - from sound waves to thought
What are the 2 forms of language?
Auditory (spoken)
Visual (written or signed)
What biological systems does language involve?
Auditory system, visual system, motor system, memory
What is aphasia?
Disorders of speaking and listening caused by stroke, tumour or head injury
What is dementia?
Progressive, degenerative brain disorder which can also affect speech and language
What happened to ‘Tan’ (Broca, 1861)?
French hospital patient with lesion that resulted in:
- single syllable speech (“tan”)
- good intonation
- obvious frustration at deficit
Also lost use of right arm & hand
What did an autopsy reveal about ‘Tan’ after his death? (Broca, 1861)
A lesion in a region in his left frontal lobe –> Broca’s area
What is Broca’s aphasia?
‘expressive’ or ‘production’ aphasia:
slow, deliberate, effortful speech production
non-fluent
omission of grammatical markers
BUT, comprehension is unaffected
Damage to Broca’s area (LEFT hemisphere only)
What happened to Wernicke’s (1874) patients?
Case report on 2 patients
- Relatively fluent speech
- Create new words - ‘neologisms’
- Severely impaired comprehension
What did Wernicke (1874) find in the post mortems of his 2 patients?
Lesion in a region of the left temporal lobe (Wernicke’s area)
What are some of the main differences between Broca’s (non-fluent, expressive) aphasia and Wernicke’s (fluent, receptive) aphasia?
- Those with Broca’s aphasia are generally aware of there deficit while those with Wernicke’s aphasia are generally unaware
- Those with Broca’s aphasia have dysfluent speech production whilst those with Wernicke’s aphasia are fluent but speech is usually content-free (Jargon)
- Those with Broca’s aphasia produce very few function words whereas those with Wernicke’s aphasia often use function words appropriately but content words are often replaced with neologisms
- Those with Broca’s aphasia have agrammatism in comprehension as well as production but are able to comprehend speech whereas those with Wernicke’s aphasia have severe comprehension deficits
What are circumlocutions?
Talking around a specific word
What are paraphasias (+ examples)?
A language output error associated with aphasia
Phonemic paraphasia, Neologistic paraphasia, Semantic paraphasia, perseverative paraphasia
What is phonemic paraphasia?
incorrect phonemes are substituted eg. pike/pipe
What is neologistic paraphasia?
the use of non-real words in place of the intended word. eg. Pinwad/light
What is semantic paraphasia?
when an entire word is substituted for the intended word. eg. girl/wife
What is perseverative paraphasia?
previous responses persist and interfere with retrieval/production
What is the Wernicke-Geschwind model (Geschwind, 1972) based on?
Neurobiological bases of language based on studies of brain impairment
What is the ‘heard word’ pathway of the Wernicke-Geschwind model?
Heard word –> Auditory cortex –> Wernicke’s area (decodes sounds for meaning) –> Broca’s area (activates speech plan; grammar) –> motor cortex –> speech
What is the ‘seen word’ pathway of the Wernicke-Geschwind model?
Seen word –> Visual cortex –> Angular gyrus –> Wernicke’s area (decodes sounds for meaning) –> Broca’s area (activates speech plan; grammar) –> motor cortex –> speech
What is the arcuate fasciculus?
a bundle of axons that connects the temporal cortex and inferior parietal cortex to locations in the frontal lobe. One of the key roles of the arcuate fasciculus is connecting Broca’s and Wernicke’s areas
What is conduction aphasia?
Fluent speech (relatively spared Broca’s area)
Good comprehension (relatively spared Wernicke’s area)
BUT Inability to repeat spoken language
What causes conduction aphasia?
Lesion to arcuate fasciculus - disrupts transfer from WA to BA = difficulty in repeating words but spoken comprehension and ability to speak spontaneously may be OK
What happens to language when there is a lesion to angular gyrus?
disrupts flow from visual cortex = difficulty saying words seen but not words heard (word blindness)
What is word deafness and what causes it?
Inability to understand spoken words
Lesions of fibre tracts from primary auditory cortex to posterior temporal regions
What is global aphasia?
- The most severe form of aphasia
- Can produce few recognizable words (if any) and understand little or no spoken language
- Verbal stereotypy – repeat a sound/phrase over and over in an attempt to communicate
- Can no longer read or write
- Preserved intellectual and cognitive capabilitiesunrelated to language and speech
What causes global aphasia?
A result of damage to theleft perisylvian cortex
Often seen straight after stroke/trauma and can improve
If damage is extensive, may be permanent
What is apraxia of speech?
- Difficulty initiating and executing voluntary movement patterns necessary to produce speech despite normal muscle strength.
- Slowed speech, abnormal prosody, distortions of speech sounds
- Specific neural basis unclear
BUT comprehension is fine
What is dysarthia?
Difficult or unclear articulation of speech
BUT comprehension is fine
What causes dysarthia?
- Disruption of muscular control due to lesions of either the central or peripheral nervous systems
- Messages controlling the motor movements for speech is interrupted
What hemisphere is predominantly responsible for language and what is this suggested by?
Left hemisphere - strongest activation
What is lateralisation?
The tendency for a given psychological function to be served by one hemisphere, with the other hemisphere either incapable or less capable of performing the function
In what way does the planum temporale demonstrate brain asymmetry?
Larger on the left in approx 65% of people - also evident in newborns
What is the right ear advantage?
The right ear projects to the left hemisphere which is responsible for language therefore if 2 different syllables are presented to the right and left ear at the same time, a participant would only repeat the right-ear syllable
What is the right visual field advantage?
According to Ellis (2004) the RVF read on average quicker and more accurately
What is the Wada technique? (Wada & Rasmussen, 1960)
Inject fast-acting anaesthetic (sodium amytal) into carotid artery supplying blood to left hemisphere.
Anaesthesia of left hemisphere and consequent immobility in contra-lateral (right) limbs and speech disruption
How does handedness affect hemisphere dominance?
Most people, regardless of handedness, are LH dominant for language
BUT
When RH dominance occurs, it’s more common in left handed people
backed up by fMRI data - LH dominant for speech production in >95% of right-handers vs ~ 80% of left-handers (McKeever et al., 1995).
What did Sperry (1969) find in their split brain study?
Present object / word in left visual field –> R.Hemisphere –> can’t name object
Present object / word in right visual field –> L.Hemisphere –> can name object
When can the right hemisphere take over in language?
Although language is associated with the left hemisphere, in some cases of early damage the right hemisphere can ‘take over’
What did Smith and Sugar (1975) find in their case study of a 5 1/2 year old boy who had a left hemispherectomy to treat epilepsy?
at 26:
typical language
typical verbal and non-verbal reasoning
a successful business executive studying part-time for a sociology degree
What are the roles of the right hemisphere in language?
- prosody (intonation, emphasis and rhythm)
- pragmatic language skills (using language appropriately)
- Understanding info from language that is not communicated by word meaning eg. sarcasm
What is the left hemisphere responsible for?
controls right sided movement
Gets touch information from right side
Auditory information (mainly) from right ear
Visual information from right visual field (not right eye)
Speech (Broca’s aphasia)
What is the right hemisphere responsible for?
Controls left sided movement
Gets touch information from left side
Auditory information (mainly) from left ear
Visual information from left visual field (not left eye)
Subtle language (e.g., intonation, metaphor comprehension)
Visuo-spatial attention
