Chapter 16 - Lateralization/split Brain/language Flashcards
Cerebral commissures
Tracts that connect the left and right cerebral hemispheres.
Name some cerebral commissures
Hippocampal commissures Corpus callosum Massa intermedia Anterior commissure Optic chiasm Posterior commissure
Lateralization of function
The differences between the major functions of the left and right hemisphere
Aphasia
A brain-damage-produced deficit in the ability to produce or comprehend language.
Broca’s area
The area of the inferior prefrontal cortex of the left hemisphere hypothesized by Broca to be the center of speech production.
Hugo-Karl Liepmann found that ______, like aphasia, is almost always associated with the left-hemisphere damage, despite the fact that its symptoms are bilateral.
apraxia
Apraxia
A disorder in which patients have great difficulty performing movements when asked to do so out of context but can readily perform them spontaneously in natural situations.
The combined impact of the evidence that the ______ hemisphere plays a special role in both language and voluntary movement led to the theory of _______.
Left,
Cerebral dominance
Theory of cerebral dominance.
Which is referred to as the dominant hemisphere and which is the minor?
One hemisphere, usually the left, assumes the dominant role in the control of all complex behavioral and cognitive processes, and the other plays a minor role.
The left is referred to as dominant, right is minor.
The sodium Amytal test of language lateralization
A test involving the anesthetization of first one cerebral hemisphere and then the other to determine which hemisphere plays the dominant role in language.
The dichotic listening test
A test of language lateralization in which two different sequences of three spoken digits are presented simultaneously, one to each ear, and the subject is asked to report all of the digits heard.
Dextrals
Right handers
Sinestrals
Left-handers
Corpus callosum
The largest cerebral commissure
There are two routes by which visual information can cross from one eye to the contralateral hemisphere:
Via the corpus callosum or via the optic chiasm
Scotoma
Area of blindness
Most efforts to identify interhemispheric differences in brain anatomy have focused on the size of three areas of cortex that are important for language:
The frontal operculum,
The planum temporale,
The Heschl’s gyrus.
The frontal operculum
The area of frontal lobe cortex that lies just in front of the face area of the primary motor cortex; in the left hemisphere, it is the location of Broca’s area.
The area of frontal lobe cortex that lies just in front of the face area of the primary motor cortex; in the left hemisphere, it is the location of Broca’s area.
The frontal operculum
The __________ lies in the posterior region of the lateral fissure; it is thought to play a role in the comprehension of language and is often referred to as Wernicke’s area.
Planum temporale
The planum temporale
The planum temporale lies in the posterior region of the lateral fissure; it is thought to play a role in the comprehension of language and is often referred to as Wernicke’s area.
Heschl’s gyrus
Located in the lateral fissure just anterior to the planum temporale in the temporal lobe; it is the location of primary auditory cortex.
Located in the lateral fissure just anterior to the planum temporale in the temporal lobe; it is the location of primary auditory cortex.
Heschl’s gyrus
There are two serious difficulties in studying anatomical asymmetry of the language areas:
- their boundaries are unclear, with no consensus on how best to define them.
- there are large difference among healthy people in the structure of these cortical language areas.
Analytic-Synthetic Theory
Holds that there are two basic modes of thinking– an analytic mode and a synthetic mode– which have become segregated during the course of evolution in the left and right hemispheres, respectively.
According to this theory, the left hemisphere operates in a logical, analytical, computerlike fashion; the right hemisphere is a synthesizer, which organizes and processes information in terms of gestalts, or wholes.
Motor theory
The motor theory of cerebral assymetry holds that the left hemisphere is specialized not for the control of speech specifically but for the control of fine movements, of which speech is only on category.
Support for motor theory of cerebral asymmetry:
Shortcomings of motor theory of cerebral asymmetry:
- support comes from reports that lesions that produce aphasia often produce other motor deficits.
- one shortcoming is that it does not suggest why motor function became lateralized in the first place.
Linguistic theory of cerebral asymmetry.
Says that the primary role of the left hemisphere is language; this is in contrast to the analytic-synthetic and motor theories, which view language as a secondary specialization residing in the left hemisphere because of that hemisphere’s primary specialization for analytical thought and skilled motor activity, respectively.
Is cerebral asymmetry exclusive to the hominin brain?
No.
There is evidence of lateralization of function in many vertebrates that evolved long before humans did.
The discovery of examples of cerebral lateralization in species from all five vertebrate classes suggests that cerebral lateralization must have _________.
Survival advantages.
Two fundamental advantages to cerebral lateralization:
1- In some cases it may be more efficient for the neurons performing a particular function to be concentrated in one hemisphere.
2- In some cases, two different kinds of cognitive processes may be more readily performed simultaneously if they are lateralized to different hemispheres.
Motor theory of speech perception
Proposes that the perception and comprehension of speech depends on the words activating the same neural circuits in the motor system that would be activated if the listener said the words.
(Wernicke-Geschwind model)
The ____ gyrus translates the visual form of a read word into an auditory code.
Angular
(Wernicke-Geschwind model)
The ________ cortex controls the muscles of articulation.
Primary motor
(Wernicke-Geschwind model)
The ________ cortex perceives the written word.
Primary visual
(Wernicke-Geschwind model)
________ area is the center for language comprehension.
Wernicke’s
(Wernicke-Geschwind model)
The _______ cortex perceived the spoken word.
Primary auditory
(Wernicke-Geschwind model)
_______ area contains the programs of articulation.
Broca’s
(Wernicke-Geschwind model)
The left _______ carries signals from Wernicke’s area to Broca’s area.
arcuate fasciculus
The cerebral _______ connect the two hemispheres.
commissures
Left-hemisphere damage plays a special role in both aphasia and _______.
apraxia
Cortex of the left inferior prefrontal lobe because known as _________.
Broca’s area
One common test of language lateralization is invasive; it involves injecting _________ into the carotid artery.
sodium amytal
Some evidence suggests that the brains of males are _______ lateralized than the brains of females.
more
The _______ is the largest cerebral commissure.
corpus callosum
cross-cuing
Nonneural communication between hemispheres that have been separated by commissurotomy.
Helping hand phenomenon
The redirection of one hand of a split-brain patient by the other hand.
Z lens
A contact lens that is opaque on one side (left or right) and thus allows visual input to enter only one hemisphere of a split-brain subject, irrespective of eye movement.
Responding to a question you heard (Wernicke-Geshwind Model).
1) Primary auditory cortex - perceiving sound.
2) Wernicke’s area - auditory code linked to meaning
3) Arcuate fasciculus - Wernicke’s area to Broca’s area.
4) Broca’s Area - motor programming of response.
5) Primary motor cortex - sending information to the muscles
Interpreter
A hypothetical mechanism that is assumed to reside in the left hemisphere and that continuously assesses patterns of events and tries to make sense of them.
Chimeric figures test
A test of visual completion in split-brain subjects that uses pictures composed of the left and right halves of two different faces.
Visual completion
The completion or filling in of a scotoma by the brain.
Expressive
Pertaining to the generation of language; that is, pertaining to writing or talking.
Receptive
Pertaining to the comprehension of language and speech.
Wernicke’s aphasia
A hypothetical disorder of language comprehension with no associated deficits in speech production.
Arcuate fasciculus
The major neural pathway between Broca’s area and Wernicke’s.
Conduction aphasia
Aphasia that is thought to result from damage to the neural pathway between Broca’s area and Wernicke’s area. Characterized by intact auditory comprehension, fluent (yet paraphasic) speech production, but poor speech repetition.
Angular gyrus
The gyrus of the posterior cortex at the boundary between the temporal and parietal lobes, which in the left hemisphere is thought to play a role in reading.
Alexia
A specific inability to read; one that does not result from general visual, motor, or intellectual deficits.
Agraphia
A specific inability to write; one that does not result from general visual, motor, or intellectual deficits.
Global aphasia
Severe disruption of all language-related abilities.
Phoneme
The smallest unit of sound that distinguishes among various words in a language.
Phonological analysis
Analysis of the sound of language.
Grammatical analysis
Analysis of the structure of language.
Semantic analysis
Analysis of the meaning of language.
Dyslexia
A pathological difficulty in reading, one that does not result from general visual, motor, or intellectual deficits.
Developmental dyslexia
Dyslexias that become apparent when a child tries to learn to read but has little success.
Acquired dyslexias
Dyslexias caused by brain damage in people already capable of reading.
Lexical procedure
A procedure for reading aloud that is based on specific stored information acquired about written words.
Surface dyslexia
A reading disorder in which the lexical procedure is disrupted while the phonetic procedure is not.
-Patients have lost their ability to pronounce words based on their specific memories of the words (i.e., they have lost the lexical procedure), but they can still apply rules of pronunciation to their reading (i.e., they can still use the phonetic procedure).
Deep dyslexia
A reading disorder in which the phonetic procedure is disrupted while the lexical procedure is not.
-Also called phonological dyslexia. Patients have lost their ability to apply rules of pronunciation in their reading (i.e., they have lost the phonetic procedure), but they can still pronounce familiar words based on their specific memories of them (i.e., they can still use the lexical procedure). Accordingly, they are completely incapable of pronouncing nonwords and have difficulty pronouncing uncommon words and words whose meaning is abstract.
Hemispherectomy
The removal of one cerebral hemisphere.
Estimates of the overall incidence of developmental dyslexia among English-speaking children range from _____ to ______, depending on the criteria that are employed to define dyslexia, and the incidence is ______ to _______ times higher among ______.
5.3%,
11.8%,
two,
three,
boys than girls.
Much of the study of lateralization of function has focused on the right hemisphere because
the special abilities of the left hemisphere have been more apparent.
Although adults have difficulty discriminating among many language sounds that are not present in the languages that they speak, ___________ can discriminate among the sounds of all languages.
10-month old infants
Each hemisphere of a human split-brain patient is capable of completing visual patterns. That is why on the chimeric figures test, each hemisphere sees
a complete, but different, face.
Brain-damage-produced deficits in language-related ability are generally referred to as
aphasia
In comparison to the causes of developmental dyslexia, the causes of acquired dyslexia tend to be more
obvious
Areas of the brain that interpret the meaning of a word are said to be performing a __________ analysis.
semantic
During language tests, PET and fMRI typically reveal greater activity in
the left hemisphere
Cognitive neuroscientists interested in the brain mechanisms of language have sought to understand the specific parts of the brain that mediate
language’s constituent cognitive processes.
Theoretically, Broca’s area is to Wernicke’s area as
language production is to language comprehension.
Evidence suggests that the naming of different categories of nouns (such as faces, animals, or tools) is each mediated by a different part of the
temporal lobe
Deep dyslexics most often have extensive damage to the left-hemisphere language areas, suggesting that the disrupted phonetic procedure is widely distributed in the _______ areas of the left hemisphere.
frontal and temporal
Three premises define the cognitive neuroscience approach to language and differentiate it from the Wernicke-Geschwind model
Premise 1:
The use of language is mediated by activity in all the areas of the brain that participate in the cognitive processes involved in the particular language-related behavior. Complex processes such as speech, comprehension, or reading are the combination of several constituent cognitive processes, which may be organized separately in different parts of the brains. Cognitive neuroscientists typically divide analysis of the constituent cognitive processes involved in language into three categories: phonological analysis, grammatical analysis, and semantic analysis.
Cognitive neuroscientists typically divide analysis of the constituent cognitive processes involved in language into three categories:
phonological analysis (analysis of the sound of language), grammatical analysis (analysis of the structure of the language), semantic analysis (analysis of the meaning of language).
Three premises define the cognitive neuroscience approach to language and differentiate it from the Wernicke-Geschwind model
Premise 2:
The areas of the brain involved in language are not dedicated solely to that purpose. Cognitive neuroscience approach assumes that many of the constituent cognitive processes involved in language also play roles in other behaviors.
Three premises define the cognitive neuroscience approach to language and differentiate it from the Wernicke-Geschwind model
Premise 3:
Because many of the areas of the brain that perform specific language functions are also parts of other funcional systems, these areas are likely to be small, widely distributed, and specialized. In contrast, the language areas of the Wernicke-Geschwind model are assumed to be large, circumscribed, and homogeneous.
The Wernicke-Geschwind model rested heavily on the analysis of brain-damaged patients, whereas researchers using the cognitive neuroscience approach also employ ______ in studying the localization of language in healthy volunteers.
an array of other techniques– most notably, functional brain imaging
The first large-scale electrical brain-stimulation studies of humans were conducted by _____ in the 1940s. One purpose of the studies was to map the _____ areas of each patient’s brain so that tissue involved in language could be avoided during the surgery. The mapping was done by assessing the responses of conscious patients, who were under local anesthetic, to stimulation applied to various points on the cortical surface.
Wilder Penfield (and colleagues), language areas.
_____ received a Nobel Prize for his research on split-brain patients.
Sperry
Commisurotomy is an effective treatment for severe cases of ______.
epilepsy
The two hemispheres of a split-brain patient can communicate via an external route; such external communication has been termed ______.
cross-cuing
Damage to the ______ hemisphere is more likely to produce ipsilateral motor problems.
left
Traditionally, musical ability, spatial ability, and _______ have been viewed as right-hemisphere specializations.
emotions
A neural mechanism metaphorically referred to as the interpreter is assumed to reside in the ______ hemisphere.
left
Because broad categories of abilities do not appear to be the units of cerebral lateralization, researchers have turned to studying the laterality of _____ cognitive processes.
constituent
Three common theories of cerebral asymmetry are the analytic-synthetic theory, the motor theory, and the ______ theory.
linguistic
Broca’s area plays a role in speech production, but there is now strong evidence that Broca’s area and other areas of motor cortex also play a role in language _______.
comprehension
Language has been called a human instinct because
it is so readily and universally learned by infants.
At ____ months of age, infants say little, but _____ month old infants speak in complete sentences and use over 500 words.
10,
30
At 10 months of age, infants _____, but 30-month-old infants _____.
say little,
speak in complete sentences and use over 500 words.
From month 10-30, the plastic infant brain
reorganizes itself to learn its parents’ languages.
At 10 months, human infants can _____, but by 30 months, they can _____.
- distinguish the sounds of all human languages,
- readily discriminate only those sounds that compose the languages to which they have been exposed.
Surgery that destroys all of Broca’s area but little surrounding tissue typically has ______.
no lasting effects on speech.
-Some speech problems were observed after the removal of Broca’s area, but their temporal course suggested that they were products of postsurgical edema (swelling) in the surrounding neural tissue rather than of the excision (cutting out) of Broca’s area itself.
No aphasic patients have damage restricted to _____.
Broca’s area or Wernicke’s area.
______ published the first large-scale study of the effects of cortical stimulation on speech.
Penfield and Roberts (1959)
Issues with Wernicke-Geschind model
- Damage restricted to the boundaries of the Wernicke-Geschwind cortical areas often has little lasting affect on the use of language–aphasia is typically associated with widespread damage.
- Brain damage that does not include any of the Wernicke-Geschwind areas can produce aphasia.
- Broca’s and Wernicke’s aphasias rarely exist in the pure forms implied by the Wernicke-Geschwind model; aphasia virtually always involves both expressive and receptive symptoms.
- There are major differences in the locations of cortical language areas in different people.
A reading disorder in which the phonetic procedure is disrupted while the lexical procedure is not.
-Also called phonological dyslexia. Patients have lost their ability to apply rules of pronunciation in their reading (i.e., they have lost the phonetic procedure), but they can still pronounce familiar words based on their specific memories of them (i.e., they can still use the lexical procedure). Accordingly, they are completely incapable of pronouncing nonwords and have difficulty pronouncing uncommon words and words whose meaning is abstract.
deep dyslexia
The smallest unit of sound that distinguishes among various words in a language.
phoneme
A specific inability to read; one that does not result from general visual, motor, or intellectual deficits.
alexia
Severe disruption of all language-related abilities.
global aphasia
Aphasia that is thought to result from damage to the neural pathway between Broca’s area and Wernicke’s area. Characterized by intact auditory comprehension, fluent (yet paraphasic) speech production, but poor speech repetition.
conduction aphasia
A reading disorder in which the lexical procedure is disrupted while the phonetic procedure is not.
-Patients have lost their ability to pronounce words based on their specific memories of the words (i.e., they have lost the lexical procedure), but they can still apply rules of pronunciation to their reading (i.e., they can still use the phonetic procedure).
surface dyslexia
A procedure for reading aloud that is based on specific stored information acquired about written words.
lexical procedure
A specific inability to write; one that does not result from general visual, motor, or intellectual deficits.
agraphia
The ______ procedure dominates in the reading of familiar words; the _______ procedure dominates in the reading of unfamiliar words.
lexical,
phonetic.
