Chapter 13 Neurolinguistics Flashcards
How many nerve cells in the brain
10 billion nerve cells, or neurons, arranged in complex networks. Each cell can be directly linked with up to 10,000 others.
“lower” brains structures (close to spinal cord)
shared by almost all animals.
maintain functions such as respiration, heart rate, and muscle coordination.
cortex (outermost layer)
This structure is absent in reptiles and amphibians, and makes up a higher proportion of the brain in primates and their closer evolutionary relatives than it does in other mammals.
folded in on itself, which increases its surface area.
what is a sulcus (plural: sulci)
The inward part of a cortical fold
what is a gyrus (plural: gyri).
the outward part of a cortical fold
what are fissures
Deep sulci.
The longitudinal fissure separates the
cerebral hemispheres.
what is the corpus callosum
A bundle of nerve fibres, the connection between the cerebral hemispheres
cerebral hemispheres
two sides of the brain, the left and right cerebral hemispheres are anatomically and functionally separate
control contralateral functions of the body, i.e. those on the opposite side
left cerebral hemisphere
controls analytic abilities, such as arithmetic. is primarily responsible for language
Right cerebral hemisphere
controls more holistic tasks, such as recognition of faces and melodies
Right-handed people
Most right-handed people are left-lateralized for language.
Right-handed people- left hemisphere removed
• If their left hemisphere is surgically removed (for example, to treat severe epilepsy), they typically cannot process complex syntactic patterns, but retain some comprehension ability.
Right handed people- right hemisphere removed
• If their right hemisphere is surgically removed, they have difficulty understanding jokes and metaphors (like He was wearing a loud tie).
Left handed people
tend to be less lateralized for language.
lobes
hemispheres are further divided into
lobes.
where is the central sulcus
behind the frontal lobe and in front of the parietal lobe.
where is the Sylvian fissure
above the temporal lobe, separates it from the frontal/parietal lobes
occipital lobe
not separated by a fissure, but falls behind the parietal lobe
4 lobes of the brain
Frontal lobe (at the front), Temporal lobe (at the bottom), occipital lobe (at the back), Parietal lobe (at the top)
autopsy
a traditional technique for studying the areas of the brain involved in different language disorders
Careful observations of a living patient’s behaviour are recorded; after death, damage to the brain is examined
Computerized axial tomography (CT scanning)
uses X-rays to provide a 3D static image of the brain, identifying lesions and tumours.
Positron emission tomography (PET)
uses a radioactive tracer to track glucose absorption in the brain, which is higher in areas of activity.
Functional magnetic resonance imaging (fMRI)
uses a powerful (and expensive!) magnet to measure blood deoxygenation, with no radioactive tracer.
Magnetoencephalography (MEG)
uses sensors to measure tiny magnetic fields on the surface of the scalp. non-invasive and has the same temporal resolution as ERP.
better spatial resolution, since magnetic fields do not extend as far from their source as electrical potentials do
What part of the brain is active during speaking?
Broca’s area
What part of the brain is active during reading?
occipital lobe and the angular gyrus
dichotic listening study
Another neurolinguistic technique in which different auditory stimuli are presented to each ear.
right ear advantage
arises for words, numbers, and Morse code, because of the more direct connection with the left hemisphere.
left ear
shows an advantage for melodies and environmental sounds such as birdsong
Split-brain experiments
after the corpus callosum is severed, demonstrate that the right hemisphere is mute.
a blindfolded split-brain patient can name an object placed in their right hand, but not in their left
Aphasia
loss of language ability resulting from brain damage. Usually from a stroke can also occur from blows to the head, brain infection, brain tumours, and brain hemorrhage
Aphasia stats
affects more than 1 million people in North America; it is equally common in men and women, and most likely to occur after age 50
Non-fluent (or motor) aphasia
arises from damage to the frontal lobe. The most severe type is called global aphasia, which results in muteness.
Broca’s aphasia
resulting from damage to the lower posterior (rear) portion of the left frontal lobe, called Broca’s area.
Broca’s aphasia results in what kind of speech?
speech of Broca’s aphasics is halting, with many periods of silence, dysprosody (the absence of normal sentence intonation), and phonemic paraphasias
… har eat … wit … pun
‘It’s hard to eat with a spoon.’
tend to omit function words, yielding telegraphic speech. also tend to omit inflectional affixes
Broca’s aphasia grammar
Broca’s aphasics have difficulty judging the grammaticality of sentences with syntactic errors Examples: The boy ate it up. *Boy ate it up. *The boy ate up it. The boy ate up the cake.
Broca’s aphasia passives
have difficulty interpreting passives correctly, when pragmatic (real-world) knowledge fails to identify the correct interpretation Examples: The mouse was chased by the cat. The dog was chased by the cat. The cat was chased by the mouse.
Broca’s aphasia semantics
does not seem to be involved in the semantic relationships between words, or in the relationship between language and thought. typically aware of their language deficit.
fluent (or sensory) aphasia
no difficulty in producing language, but the content of what is produced is disordered. most important type of fluent aphasia is Wernicke’s aphasia
Wernicke’s aphasia
resulting from damage to the upper posterior portion of the left temporal lobe, called Wernicke’s area
speech typically sounds fine, no long pauses, correct intonation, use of function words, and correct word order. But makes very little sense
Jargon aphasia
severe form of Wernicke’s aphasia in which phonemes are randomly selected. Speech has correct intonation, but few recognizable words
Wernicke’s aphasia patients..
lack coherent trains of thought
have difficulty doing sequenced tasks such as buying groceries or doing laundry
typically unaware of their disorder
acquired dyslexia
The impairment of reading ability following
brain damage
acquired dysgraphia
The impairment of writing ability following brain damage
paragraphia
error in writing that often omits the letters corresponding to sounds they would omit (Broca’s aphasiacs do this)
Broca’s aphasia patients (writing)..
make paragraphia errors
also omit function words and inflectional morphology in spontaneous writing
have good silent reading skills, but their reading aloud is telegraphic
These errors suggest a deep deficit, not just an articulatory one
Wernicke’s aphasics (writing)..
typically retain good spelling and handwriting, but what they write makes little sense
Their reading comprehension is severely impaired as well
damage to angular gyrus
Acquired reading and writing deficits also occur on their own, usually following damage in and around the angular gyrus
English orthography requires..
both knowledge of spelling-to-sound rules (for regular spellings like bat) and recognition of whole words (for irregular spellings like yacht)
phonological dyslexia
patients lose the ability to use the spelling-to-sound rules; they can only read familiar words
Given a nonsense word like blug, they either cannot read it, or produce a similar real word (blue, bug)
surface dyslexia
patients lose the ability to recognize whole words
• They overregularize the pronunciation of irregular spellings (e.g. yacht → /jɑtʃt/).
• They comprehend a word like worm as they pronounce it (“warm”), not as it is spelled.
Aphasia and linguistic theory
Incorporating linguistic theory has radically increased the sophistication of the research questions posed in studies of aphasia.
This has yielded a deeper understanding of aphasic phenomena.
Evidence that inflection and derivation are distinct
Broca’s aphasics tend to drop inflectional morphology, but preserve derivational morphology
deep dyslexia (evidence for a semantic organization of the lexicon)
patients will produce a word that is semantically related to a word they are asked to read (e.g. mother → ‘father’).
provides independent evidence for a semantic organization of the lexicon
evidence for rules and linguistic competence
Broca’s aphasics will produce the unrestricted form of a morpheme, rather than the allomorph resulting from the application of a rule (e.g. illegal → ‘inlegal’)
agrammatism
Happens in Broca’s aphasia, the absence of certain key grammatical abilities
words typically omitted by Broca’s aphasics are items such as it, is, to, or a
provides evidence between functional categories and lexical categories
default strategy for Broca’s aphasics’ difficulty with passives
treats the first NP in a sentence as an agent. This works with active sentences, but not with passives.
Broca’s aphasics typically guess at the meaning of reversible passives (like The cat was chased by the dog)—incorrectly about 50% of the time, not 100%.
(evidence against default strategy)
Various aspects of language represented in different parts of the brain:
- Broca’s area plays a crucial role in speech articulation and syntax.
- Wernicke’s area plays a key role in language comprehension.
- The angular gyrus plays a special role in reading.
