Chapter 19: Language and Lateralization Flashcards
Lateralization
One hemisphere being mire specialized in one domain compared to the other hemisphere.
What is the most well known lateralization of function?
Language
What was discovered about hemispheres in the early 20th century?
The two hemispheres are not identical in terms of language functioning.
What was discovered over time about the cerebral hemispheres and their function?
The cerebral hemispheres are lateralized in terms of function.
What notion of cerebral dominance is incorrect?
The theory of being “left” or “right” brained
Where does a lot of information about hemispheric asymmetry come from?
“Split-brain” individuals
Split-Brain Individual
The corpus callosum has been cut.
What do visual fields connect to?
The opposite hemisphere
How is language visually produced in the left visual field?
- The image seen in the left visual field goes to the right hemisphere.
- The information crosses back into the left hemisphere where it is converted to language.
How is language visually produced in the right visual field?
- The image seen in the right visual field goes to the left hemisphere.
- The information stays in the left hemisphere where it is processed into language.
What brings stimuli from the visual field to the opposite hemisphere in split brain individuals?
Subcortical pathways
How do split brain individuals process information from the right hemisphere to language.
They do not
- split corpus callosum prevents right hemisphere from communicating with language
= verbal responses to stimuli are IMPOSSIBLE
What visual field allows split brain individuals to verbally respond to stimuli?
Right visual field
Why can’t an individual explain why they pointed to a picture when they are asked?
The left hemisphere is trying to communicate with the right hemisphere after the task is already done.
Is the right hemisphere completely uninvolved in language in split brain individuals?
No - It can still recognize simple words and participate in the emotional context of verbal material.
What is the right hemisphere specialized for?
- Spatial information
- Facial perception
- Attention
What is unique about the general display of split brain individuals?
They do not seem to present as “split-brain” individuals
Callosal Agenesis
People born without a corpus callosum
Can development compensate for the lack of a corpus callosum?
Yes
- Through inter-hemispheric connections
What can auditory systems be used to investigate?
Lateralization
Dichotic Presentation
You present two different sounds to the two ears at the same time.
Which hemisphere processes sounds the most?
The left hemisphere
How is verbal information processed by the left ear?
- It is processed by the right auditory cortex.
- Transmitted back to the speech systems in the left hemisphere
= patient repeats word
How is verbal information processed by the right ear?
- Processed by the left auditory cortex.
- Stays in the same hemisphere to be processed by the speech systems.
What happens when sound is present in both ears at the same time?
The information from the right ear reaches the left hemisphere first.
- Only repeats right ear information
Why is there a right ear advantage to dichotic presentation?
The right ear connects with the left auditory cortex better
language is processed within left hemisphere
Tachistoscope Test
A test in which stimuli are very briefly presented to either the left or right visual half field.
What does the tachistoscope test confirm?
- Left hemisphere is better at recognizing verbal stimuli
- Right hemisphere is better with nonverbal stimuli (visual)
When does asymmetric gene expression begin?
12-14 weeks after gestation
When do primates show greater left hemisphere activation?
When listening to other primate vocalizations
What do non-primates/mammals show preference for?
The use of limbs on one side over the other
What does evidence suggest about the planum temporale?
It is larger in the left hemisphere for most people.
Planum Temporale
A region in the upper temporal lobe that is involved in language, speech processing, and pitch processing
What does the larger size of the planum temporale seem to be related to?
General auditory processing abilities
What is an example of someone who shows differences in planum temporale size?
Musicians (larger)
Non-musicians (smaller)
What is true about the relationship between the hemispheres and language/music?
Both hemispheres contribute, but the function is generally lateralized
What is the Wada Test used for?
Used to study each hemisphere in isolation.
Explain the Wada Test
- Anesthetic amobarbital is injected into the carotid artery by a catheter.
- The injection shuts down the cerebral hemisphere on the same side of the body.
- The functions performed by the opposite hemisphere are revealed
What is an example of the Wada Test?
If you shut down the right hemisphere, the subject can still talk but not hold up their left arm.
What is the conclusion of spatial recognition from the Wada Test?
The right hemisphere is better at processing spatial stimuli
(shapes, faces, rotation of objects)
Prosopagnosia
A condition characterized by the inability to recognize faces (including your own).
How is prosopagnosia developed?
Can be acquired or genetic
How much of the population suffers from prosopagnosia?
2.5%
What happens when the right hemisphere is damaged?
Impairments in facial recognition
What needs to happen to have complete prosopagnosia?
Bilateral damage
Fusiform Gyrus
May contain subregions that are important for recognizing faces
What is prosopagnosia often associated with?
Agnosia
Agnosia
Inability to identify items, despite being able to describe them in terms of form and color; frequently individuals with large categories.
What is language considered?
A type of communication
What is language specialized towards?
Only humans; animals only communicate
What is the only way for apes to be trained in language?
Sign/symbol language
What do studies of apes likely have?
-Bias
-Experimenter influences
Can apes and chimps develop language?
Not the full capability, even with training.
What is an example of animal analogy to human language?
Bird songs
MUST BE LEARNED (same with humans and talking)
Why do male birds produce the ability to sing songs?
Males produce songs as a part of social and reproductive behavior
What are the 3 steps to male birds producing songs?
- Exposure; exposure to fathers model becomes a stored model
- Trial and Error; the male practices song to match the fathers model
- Fixing the song into permanent form
What do lesions of the direct auditory pathway in birds lead to?
The disruption of song performance at any time.
What does lesions to an indirect pathway in birds lead to?
Disruption of song acquisition
What do lesions in auditory regions in bird adulthood lead to?
No disruption to performance
What is a common behavior for primates when hearing?
Pointing their right ear towards the sound.
What are the electrical activity changes within cortical regions of primates similar to?
Human language cortical areas
Phonemes
Basic speech sounds
Morphemes
Basic units of “meaning”
Semantics
Words with meaning
What can semantics be?
A combination of morphemes
Syntax
Sentences
What is our speech affected and interpreted by?
Pragmatics and prosody
Pragmatics
The context in which things are spoken
Prosody
Emotional tone and emphasis
What happens to the human brain during development?
It adapts for language through rapid acquisition
What is an affect of a potential sensitive period of developing language?
It can be harder to learn language in adulthood
What did language most likely evolve from?
Hand and face gestures
What part of the brain is used during sign language?
The same parts as spoken language use
What happens to deaf children who do not have access to sign language?
They develop their own form of sign language
What does the evolution from hand gestures to spoken language explain?
The lateralization of language
Where does much of the understanding of language come from?
People with language impairments
Where is Broca’s area located?
The anterior frontal region
Where is Wernicke’s area located?
The temporal region
What happens when there is a lesion in Broca’s area?
Issues with speech
What happens when there is a lesion in Wernicke’s area?
Issues with language comprehension
What does injury to the supramarginal gyrus cause?
Issues with the repetition of heard speech
Supramarginal Gyrus
A region in the parietal lobe used in cortical speech
Where are most people’s language abilities found?
The left hemisphere
What does damage to language areas lead to?
Aphasia
Aphasia
An impairment in language understanding and/or production that is caused by brain injury.
What can aphasia be accompanied by?
Agraphia
Agraphia
The inability to write
Alexia
The inability to read fluently
Nonfluent Aphasia (Broca’s)
Difficulty with speech production but not with language comprehension.
What is nonfluent aphasia related to?
Damage in Broca’s area
What is often preserved in a person who suffers from nonfluent aphasia?
Automatic speech
- Small sayings
- Swear words
Fluent Aphasia (Wernicke’s)
Fluent, meaningless speech and little language comprehension.
What is fluent aphasia related to?
Damage in Wernicke’s area
What is fluent aphasia characterized by?
- Word substitutions
- New word use
What do people who suffer from fluent aphasia have difficulty with?
- Repeating words
- Understanding language
What can people who have fluent aphasia still interpret?
Facial expressions
What other disorder is common with fluent aphasia?
Anomia
Anomia
Difficulty naming objects/people
What does anomia result from?
Damage to Wernicke’s area
Global Aphasia
A total loss of ability to understand or produce language.
What does global aphasia generally result from?
Very large left-hemisphere lesions
(attacks both anterior and posterior language zones)
What did aphasia and brain lesions lead to?
Wernicke-Geschwind Model of Aphasia
Wernicke-Geschwind Model of Aphasia
The theory that Wernicke’s area and Broca’s area specialize in the receptive and expressive aspects of language.
What is the problem with the Wernicke-Geschwind Model of Aphasia?
It does not work well for explaining language
What does damage to the arcuate fasciculus produce?
Conduction aphasia
Arcuate Fasciculus
A white matter tract initially theorized to connect Wernicke’s area to Broca’s area.
Conduction Aphasia
Impairment in the repetition of words and sentences but still have fluent speech/comprehension.
What do imaging and electrophysiological recording studies show?
Large variations in regions responsible for different aspects of language
Motor Theory of Language
The left-hemisphere language zones are motor control systems that are concerned with both the precise production and the perception of extremely complex movements that go into speech.
What does the motor theory of language believe?
The Wernicke-Geschwind model is oversimplified
The differences between production and conduction are…
not very simple
Anterior Region of Left Hemisphere
Programs simple phonemes of speech.
Posterior Region of Left Hemisphere
String sounds into long sequences of movement.
What can speech sounds be simplified to?
Auditory representations of complex facial movements and gestures
What brain region is used to make facial movements?
The same region that perceived the sound
What is the problem with the motor theory?
It is too simplified
What does language involve?
A more holistic processing of multiple regions simultaneously
What do experiments use to see what areas are involved in langauge?
Electrical stimulation
What happens when specific brain sites are stimulated in bilingual individuals?
They have trouble in one language or the other (never at the same time)
Why do bilingual never have difficulty in both languages when stimulated?
Different subregions are tied to certain languages
What does speech production also involve?
Hand areas of the motor cortex
What does TMS stimulation of Broca’s area effect?
Semantic (meaningful) processing
What does TMS stimulation of Wernicke’s area effect?
Phonological (sound pattern) processing
What do PET scans during different language tasks reveal?
Overlapping distinct systems that are involved in language
What does the passive viewing of words activate?
Posterior area within the left hemisphere
What does the passive hearing of words activate?
The focus of maximum brain activation to the temporal lobes
What does the repetition of words activate?
The motor cortex on both sides
What happens to activity in Broca’s area during word repetition?
There is little activity until participants are asked to generate a verb to a given noun.
How do people in the Canary Islands communicate?
Silbo Gomero (whistling)
What do fMRIs reveal about Silbo Gomero?
It is processed in the same regions as spoken languages
Where is whistling processed in non Silbo users?
Other regions due to not recognizing it as a language
What parts of the brain does sign language use?
The same parts as verbal language
What have a number of genes been identified as?
important for language development
Williams Syndrome
A disorder characterized by fluent language function but poor performance on standard IQ tests and difficulty with spatial processing.
What is williams syndrome characterized with?
Increased fluency and mild cognitive disability
What happens to genes in williams syndrome?
About 28 genes are deleted
What does evidence suggest about stuttering?
It also has a genetic component and is partially heritable
What is considered an ancient human adaption?
Language
What are considered recent developments?
Reading and writing
Dyslexia
A reading disorder attributed to brain impairment.
What is dyslexia not necessarily related to?
Intelligence
What do people with dyslexia show larger levels of?
Differences in the brain
What do brain regions activated in dyslexia depend on?
The type of written language
What causes dyslexia with alphabet letters?
A lesion in the left temporoparietal cortex
What causes dyslexia with logographic symbols?
A lesion in the left medial frontal cortex
What are the two kinds of dyslexia?
- Acquired dyslexia
- Developmental dyslexia
Acquired Dyslexia
Occurs because of injury or disease; lesions of some kind.
Deep Dyslexia
The person reads a word as another word that has similar meaning.
What is an example of deep dyslexia?
Saying cow for horse (both animals)
What are the two kinds of acquired dyslexia?
- Deep dyslexia
- Surface dyslexia
Surface Dyslexia
The person seems to attend only to the fine details of reading.
What is a characteristic about a person reading who has surface dyslexia?
They are able to read nonsense words due to letter to sound rules
What words do people with surface dyslexia have trouble reading?
Words that do not follow letter to sound rules
What does surface dyslexia not occur in?
Languages that are perfectly phonetic
Developmental Dyslexia
Associated with brain abnormalities present from birth.
How popular is developmental dyslexia in children?
About 5% of children
What is developmental dyslexia more common in?
boys and left-handed people
What is developmental dyslexia associated with?
Neural abnormalities
What does evidence suggest about developmental dyslexia?
It may involve a lack in phonological processing (recognizing phonemes
What does developmental dyslexia involve connections between?
Connections among different systems underlying phonological processing and semantic processing
What is a neural abnormality in people who have dyslexia?
They have microscopic anomalies called..
- ectopias
- dysplasia
- micropygids
in their brain that are responsible for dyslexia
The brain is highly…
plastic/shapable
What does having a plastic brain mean?
It can recover quite a bit from injuries over time (including aphasia)
What is aphasia caused by?
Strokes
What can children show remarkable recovery from?
Left Hemispherectomies
Left Hemispherectomies
Removal of the left hemisphere
