Neuroscience Ch. 16
Evidence from functional neuroimaging studies
- No aphasic patients have damage restricted to Broca's area or Wernicke's area. - Aphasic patients almost always have significant damage to subcortical white matter. -Large anterior lesions are more likely to produce expressive symptoms, whereas large posterior lesions are more likely to produce receptive symptoms. - global aphasia is usually related to massive lesions of anterior cortex, posterior cortex, and underlying white matter. - Aphasic patients sometimes have brain damage that does not encroach on the Wernicke-Geschwind areas
Z lens
-developed by Zaidel in 1975 -limits visual input to one hemisphere of split-brain patients while hey scan complex visual material such as book pages -opaque on one side , moves with the eye permitting visual input to enter only one hemisphere, irrespective of eye movement
Broca's aphasia
-expressive aphasia -condition resulting from damage to Broca's area, causing the affected person to be unable to speak fluently, to mispronounce words, and to speak haltingly
Sodium Amytal Test
-for language lateralization -given prior to neurosurgery -results are used to plan the surgery -injection of a small amount of sodium amytal into carotid artery on one side of the neck -the injection anesthetizes the hemisphere on that side for a few min, allowing the capacities of the other hemi to be assessed. -patient asked to recite well known series and to name pictures -repeated on the other side -when the left side is anesthetized the patient goes mute
vocal communication in nonhuman primates
-have calls that are understood by conspecifics -typically a substantial difference between the capacity for vocal production and the capacity for auditory comprehension
Motor theory of cerebral asymmetry
-kimura 1979 -the left hemi is specialized not for the control of speech specifically but for the control of fine movements, of which speech is only one category -lesions that produce aphasia often produce other motor deficits
Wernicke's area
-language comprehension -discovered in 1874
planum temporale
-lies in the posterior region of the lateral fissure -thought to play a role in the comprehension of language *Wernicke's area*
Dichotic listening test
-noninvasive (administered to healthy individuals) -three pairs of spoken digits are presented through earphones -the digits of each parie are presented simultaneously, one to each ear -people tend to remember the digits presented in the right ear slightly more than the left
Second phase of Myers and Sperry's experiment
-patch is transferred to the other eye of the cat -there was no change in the control cats -the experimental cats were affected drastically: results dropped to basic of 50% and relearned with no memory of previous study
deep dyslexia
-patients have lost their abilities to apply rules of pronunciation in their reading, but they can still produce familiar words based on their specific memories of them -incapable of pronouncing nonwords and have trouble with uncommon and abstract words *lost phonetic, maintained lexical*
surface dyslexia
-patients who have lost their ability to pronounce words based on their specific memories of words, but can still apply rules of pronunciation in their reading - problems pronouncing words with uncommon rules and misapplying common rules (have rhymes with cave) *lost lexical, maintained phonetic*
Schlaug and colleagues 1995
-planum temporale asymmetry study -used MRI to measure the asymmetry of the planum temporale and relate it to the presence of perfect pitch -tended to be larger in the left hemi in people with perfect pitch
Broca's discovery in 1861
-post mortem examination on 2 aphasic patients -left-hemisphere lesion in the inferior prefrontal cortex (Broca's area)
Joseph Jules Dejerine 1892
-postmortem exam of a patient with alexia (inability to read) and agraphia (the inability to write) -no difficulty understanding or speaking speech -damage in pathways connecting the visual cortex with the left angular gyrus
7 components of the Wernicke-Geschwind model
-primary visual cortex -angular gyrus -primary auditory cortex -Wernicke's area -arcuate fasciculus -Broca's area -primary motor cortex *all are in the left hemisphere*
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 have been activated if the listener had said the words -discovery of mirror neurons supports -same area activated when you think about performing an action and when it is actually performed
Wernicke's aphasia
-receptive aphasia -poor comprehension of both written and spoken language and speech that is meaningless but still retains the superficial structure, rhythm, and intonation of normal speech
Myers and Sperry (1953)
-showed that one function of the corpus callosum is to transfer learned info from one hemi to the other -showed that when the corpus callosum is cut each hemi can function independently -each split-brained cat appeared to have 2 brains -trained cats to perform a simple visual discrimination task -presented with two panels at the end of each trial had to learn which one provided them with a food reward -had to teach and test one hemi at a time -transected both the optic chiasm and corpus callosum in each cat *revealed that one hemi working alone can learn simple tasks as rapidly as two hemis working together*
The Case of Peter the Split-Brain Patient Tormented by Conflict
-suffered from complex partial seizures beginning at the age of 8 -received a commissurotomy at age 20 (Improved his condition but did not block his seizures) -he was left hemi dominant for language - after surgery peter's right hemisphere caused him frustration completing acts that he didn't want to happen (left hand would turn off a tv show he was enjoying)
True or False: feelings of emotion appear to have difficulty being passed between the hemispheres of most split-brain patients
False! emotions are passed readily between the two
evidence from the studies of the effects of cortical damage
-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 in the surrounding neural tissue rather than of the excision - underdeveloped research on removal of Wernicke's area due to fear of removal -those with most of it removed did not have lasting language-related deficits
angular gyrus
-the area of the left temporal and parietal cortex just posterior to Wernicke's area -responsible for comprehending language related visual input
Linguistic Theory of cerebral asymmetry
-the primary role of the left hemisphere is language -based highly on study of deaf people who use ASL and suffer unilateral brain damage -left hemi damage disrupts ASL but not pantomime gestures
Specialization of the right hemisphere for emotion
-the right hemi may be superior to the left at performing some tests of emotion -no unambiguous support for this view
Paulesu and colleagues 2001
-twice as many english speakers as italian speakers are diagnosed with dyslexia - results from complexity of the two languages -compared PET activity in the brains of typical English-speaking and Italian-speaking adults as they read. -since the cognitive demands of reading aloud are different for Italian and English speakers, their volunteers might use different parts of their brains while reading - Italian readers displayed more activity in the left superior temporal lobe, whereas English readers displayed more activity in the left inferior temporal and frontal lobes
Evidence from studies of electrical stimulation of the cortex
-wilder penfield in 1940s - map the language areas of each patient's brain so the tissue involved in language could be avoided during surgery -found that sites at which stimulation blocked or disrupted speech in conscious neurosurgical patients were scattered throughout a large expanse of frontal, temporal, and parietal cortex, rather than being restricted to the Wernicke-Geschwind language areas -found no tendency for particular kinds of speech disturbances to be elicited from particular areas of the cortex
word salad
Incoherent mixture of words, phrases, and sentences associated with wernicke's aphasia
frontal operculum
Area of the 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 the *Broca's area*
Sperry and Gazzaniga
Investigated functional differences between left and right cerebral hemispheres using "split-brain" studies *split human brains have very unequal abilities in the two sides in most tasks*
cross-cuing
Nonneural communication between hemispheres that have been separated by commissurotomy
aphasia
brain damage-produced deficit in the ability to produce or comprehend language
acquired dyslexia
caused by brain damage in individuals who were already capable of reading
constituent cognitive processes
combined activity of simple cognitive processes
conduction aphasia
comprehension and spontaneous speech would be largely intact in patients with damage to the arcuate fasciculus but that they would have difficulty repeating words they had just heard
Left hemisphere
dominant hemisphere
developmental dyslexias
dyslexias that become apparent when a child is learning to read -U.S. =5-12%
anterior damage tends to result in deficits that are more...
expressive
dyselexia
is a reading disorder
What two major functions are lateralized to the left hemisphere?
language and motor abilities
sinestrals
left-handers *30 percent of sinistrals with left-hemisphere lesions and 24 percent of those with right-hemisphere lesions were diagnosed as aphasic*
Heschl's gyrus
located in lateral fissure just anterior to planum temporale in the temporal lobe; location of *primary auditory cortex*
Cerebral Dominance Theory
one hemisphere (usually left) assumes the dominant role in the control of all complex behavioral and cognitive processes and the other plays only a minor role
split brain patients
patients whose left and right hemispheres have been separated by commissurotomy
dyslexia results most commonly from a specific disturbance of...
phonological processing: the representation and comprehension of speech sounds
helping-hand phenomenon
presented with 2 different visual stimuli, the hand that "knows" may correct the other by grabbing it and redirecting it
posterior damage tends to involve deficits that are more...
receptive
language localization
refers to the location within the hemispheres of the circuits that participate in language-related activities
Dextrals
right handers *60 percent of dextrals with left-hemisphere lesions and 2 percent of those with right-hemisphere lesions were diagnosed as aphasic*
global aphasia
severe disruption of all language-related abilities
phoneme
smallest unit of sound
cognitive neuroscience approach
the approach that examines cognitive development through the lens of brain processes
Myers and Sperry Conclusion
the cat brain has the capacity to act as two separate brains and that the function of the corpus callosum is to transmit information between them
Wernicke-Geschwind model
the predominant theory of language localization
lateralization of function
the unequal representation of various psychological functions in the two hemispheres of the brain
Right Hemisphere
understands a few simple instructions but cannot speak, who receives sensory information from the left visual field and left hand, and who controls the fine motor responses of the left hand
Left Hemisphere
verbally adept, who receives sensory information from the right visual field and right hand, and who controls the fine motor responses of the right hand.
Premise 2 that defines the cognitive neuroscience approach to language
The areas of the brain involved in language are not dedicated solely to that purpose
Visual completion
The completion or filling in of a scotoma by the brain
Split brain colored light example
The right hemisphere saw the green light and heard the left hemisphere guess "red." Knowing that red was wrong, the right hemisphere initiated a frown and shook her head, no. This signaled to the left hemisphere that the answer was wrong and that it needed to be corrected.
True or False: Language abilities are the most highly lateralized of all cognitive abilities.
True!
True or false: Right-handedness may have evolved from a preference for the use of the right side of the body for feeding
True! It has been demonstrated in species of all five vertebrate classes
True or False:Split-brain patients can search for, and identify, a visual target item in an array of similar items more quickly than healthy controls can
True! the two split hemispheres are conducting two independent searches.
Superiority of the left hemi in controlling ipsilateral movement
When complex, cognitively driven movements are made by one hand, most of the activation is observed in the contralateral hemisphere, as expected.some activation is also observed in the ipsilateral hemisphere, and these ipsilateral effects are substantially greater in the left hemisphere than in the right
arcuate fasciculus
a bundle of axons that connects Wernicke's area with Broca's area; damage causes conduction aphasia
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
Milner 1974 finding
almost all right-handed patients without early left-hemisphere damage had left-hemisphere specialization for speech(92 percent), most left-handed and ambidextrous patients without early left-hemisphere damage had left-hemisphere specialization for speech (69 percent), and early left-hemisphere damage decreased left-hemisphere specialization for speech in left-handed and ambidextrous patients (30 percent).
Premise 3 that defines the cognitive neuroscience approach to language
areas are likely to be small, widely distributed, and specialized
lexical procedure
based on specific stored information acquired about written words
phonetic procedure
Reader looks at the word, recognizes the letters, sounds them out, and says the word
The Case of W.L.: The Man Who Experienced Aphasia for Sign Language
- a congenitally deaf, right-handed male - 7 months before test was in hospital for right side weakness and motor problems -CT revealed a frontotemporoparietal stroke -he was making errors in signing and was having difficulty understanding signs -his sign-language aphasia was specific to language
Damasio's PET study of naming
- look selectively at the temporal-lobe activity involved in naming objects within particular categories - Images of famous faces, animals, and tools - Activity while judging image orientation subtracted from activity while naming - Left temporal lobe areas activated by naming varied with category - Activity seen well beyond Wernicke's area
Bavelier's fMRI study of reading
-1997 -used fMRI to measure the brain activity of healthy volunteers while they read silently -used sensitive fMRI machines=increased accuracy -recorded during reading of sentences (less simple) -*3 important points* 1. The areas of activity were patchy; that is, they were tiny areas of activity separated by areas of inactivity. 2. The patches of activity were variable; that is, the areas of activity differed from participant to participant and even from trial to trial in the same participant. 3. Although activity was often observed in parts of the classic Wernicke-Geschwind areas, it was widespread over the lateral surfaces of the brain. *more activity in left hemi that extended far beyond structures in the Wernicke-Geschwind model*
Analytic-synthetic theory of cerebral asymmetry
-2 basic modes of thinking (analytic and synthetic) that have become segregated during the course of evolution -left hemi: logical, analytical, computerlike fashion, analyzing and abstracting stimulus input sequentially and attaching verbal labels -right hemi: y a synthesizer, which organizes and processes information in terms of gestalts, or wholes -problem=vaugeness
Superior Music Ability of the Right Hemisphere
-Kimura 1964 -compared the performance of 20 Right handers on the standard digit version of dichotic listening test with their performance on a version of the test involving the dichotic presentation of melodies. -simultaneously played 2 different melodies (one in each ear) and then had to identify the two out of four -The right ear was superior in the perception of digits and the left ear was superior in the perception of melodies
Superiority of the Right Hemisphere in Spatial Ability
-Levy 1969 -placed a 3D block of a particular shape in either the right hand or the left hand of split-brain patients . -They were then asked to point to the 2D stimulus that would best represent the 3D figure unfolded. -Found right-hemi superiority -Left hand & right hemi: rapid and silent -right hand & left hemi: hesitant and accompanied by verbal commentary *right hemi is superior to left at spatial tasks*
gestural language
-Pollick and de Waal 2007 -Chimps hand movements are more similar to human language than their vocalizations
Ojemann's findings
-Stimulation to areas far beyond the boundaries of the Wernicke-Geschwind language areas was capable of disrupting the use of language. -Each of the language tests was disrupted by stimulation at widely scattered sites. -There were major differences among the patients in the organization of their language abilities *language cortex is organized like a mosaic with the discrete columns of tissue that perform a particular function widely distributed throughout the language areas of cortex.*
The Left-Hemisphere Interpreter
-a hypothetical neuronal mechanism that continuously assesses patterns of events and tries to make sense of them -stacked light experiment: the top light flashes 80% of the time but in no particular sequence---> split-brain patients only got the answer correct 68% of the time because the left hemi was trying to figure out a deeper pattern.
Functional Brain imaging
-a volunteer engages in an activity and brain activity is monitored by positron emission tomography (PET) or functional resonance imaging (fMRI) -higher activity in the left hemi on language tests
Hugo-Karl Liepmann
-apraxia always associated with left hemi damage -despite bilateral symptoms -trouble performing movements out of context
The Case of N.I.: the Woman Who Read with Her Right Hemisphere
-at 13 she began to experience periods of aphasia -had convulsions---> speech and motor abilities deteriorated -ischemic damage to left hemi -total left hemispherectomy was done: left hemi was removed -seizures were stopped -reading performance was poor but retained abilities similar to those with someone with deep dyslexia
Premise 1 that defines the cognitive neuroscience approach to language
-constituent cognitive processes are the appropriate level at which to conduct cognitive neuroscientific analysis -3 categories 1. phonological analysis (analysis of the sound of language) 2. Grammatical analysis 3. semantic analysis (analysis of the meaning of language)
How the Wernicke-Geschwind Model works
1. in convo the auditory signals triggered by the speech of peers is received by primary auditory cortex and conducted to Wernicke's area where it is comprehended. 2. Wernicke's area generates the neural representation of the thought underlying the reply, and it is transmitted to Broca's area via the left arcuate fasciculus 3. In Broca's area, this signal activates the appropriate program of articulation that drives the appropriate neurons of your primary motor cortex and ultimately your muscles of articulation *Second* 1. When you are reading aloud the signal received by your primary visual cortex is transmitted to your left angular gyrus which translates the the visual form of the word into its auditory code and transmits it to Wernicke's area for comprehension 2. Wernicke's are then triggers the appropriate responses in your arcuate fasciculus to elicit the appropriate speech sounds
Two approaches to the studying the cerebral lateralization of memory
1. link particular memory processes with particular hemispheres 2. link the memory processes of each hemisphere to specific materials rather than to specific process
two fundamental advantages of cerebral lateralization
1. may be more efficient for the neurons performing a particular function to be concentrated in one hemisphere 2. two different kinds of cognitive processes may be more readily performed simultaneously if they are lateralized to different hemispheres
3 area of cortex that are most important for language
1. the frontal operculum 2. the planum temporale 3. Heschl's gyrus
difficulties in studying anatomical asymmetry of the language areas
1. unclear boundaries 2. large differences among healthy people in these structures
How much more likely is a male to suffer from unilateral strokes in comparison to a female?
3x *male brains are more lateralized than female brains*
heritability estimate of developmental dyslexia
50%
Vogel and Bogen
To reduce seizures, severed patients' corpus callosum *major convulsions were reduced*
Right hemisphere
minor hemisphere
