Module 6
Anatomy of a word exampe
"unfathomable" -"un": morpheme --> 2 phonemes: "u," "n" -"fathom": morpheme --> 5 phonemes: "f," "a," "th," "o," "m" -"able": morpheme --> 4 phonemes: "a," "b," "l," "e"
Connectionist model of aphasia
(Wernicke-Geschwind model) attributes language deficits to disconnections between regions of the brain's language network -arcuate fasciculus, a tract believed by some to connect Wernicke's and Broca's areas, is a key component
Broca's aphasia
(nonfluent aphasia): characterized by difficulty producing speech but good comprehension; results from damage to Broca's area
Language has both learned and unlearned components
-Analysis of a family with a rare heritable language disorder identified a gene that appears to be important for normal acquisition of language. -A heritable mutation of the FOXP2 gene causes delayed speech development. -People with the mutation exhibit different patterns of brain activation during a language task
Mirror therapy
-Another therapy uses a mirror placed so that an individual with reduced use of one arm was only able to see the unaffected arm -When making symmetrical motions, the patient learns to use the affected arm sooner; visual feedback overcomes the brain's reluctance to use that arm
Reading systems
-Brains rely on two language systems while reading: • One focuses on sounds of letters (phonology) • One focuses on meanings of whole words (semantics) -People with dyslexia often lack a connection between the two systems
Prosody
-Controlled by right hemisphere, similar to arrangement of Broca's and Wernicke's areas -Right inferior frontal gyrus for production of prosody, right temporoparietal region for comprehending prosody -Placing appropriate stress, timing, or intonation on words in sentences -Deficits- lack of comprehension of emotional tone, trouble understanding jokes or emotions, hard to relate to others in social gatherings
Infant language lernaing
-Extraordinary speed and power -Multiple connections being made, and synaptic pruning in early years -1st six months of life, infants can perceive contrasts between phonemes from all languages but lose non-native consonants by 10-12 months • Example: Japanese adults versus infants - "ra" and "la"
Language development
-From birth, babies can distinguish phonemes from every language. -Language development depends on a sensitive period. A person deprived of language during this period can't develop language skills later in life. -During the sensitive period, children can learn languages easily; adults find it much harder, and functional imaging shows they use different brain regions -before age of 7 is optimal time to learn a language
Image in Visual Field example
-In someone that does not have split brain: key is flashed in left visual field, the person says key (goes to right V1, transmist signal via corpus callosum to left hemisphere --> language is produced) -In someone with split brain: key is flashed to left visual field: nothing is said (right V1--> can't send info to left hemisphere to produce language) -split brain: right visual field, can produce speech because right visual field --> left V1 and is already in left hemisphere
Infant perception
-Infants perceive all speech contrasts used in natural language at birth or in the first few weeks of life -Infants may require a preference for the speech sounds of their native language in utero (Rapin, 1999) -Other mammals (chinchillas) also can perceive contrasts
Lip reading
-Kuhl and Meltzoff (1988) presented infants with two pictures of mouths making different speech sounds -One mouth making the "eeeee" sound -One mouth making the "ooooo" sound -When one of the sounds is played, infants looked longer at the picture of that sound, and try to reproduce the sound themselves
Competing models of language system
-Later studies revealed compartmentalization of linguistic processes such as naming, reading, speech production, and verbal memory. -Stimulation of language areas in bilingual subjects indicates that each language is affected by different areas. -People who are bilingual from an early age show a complete overlap of the two language zones
Left-handedness
-Left-handed people make up about 10- 15% of the population. -Left-handed children do not differ from right-handed children on any measure of cognitive performance. -Handedness may have a genetic component
Overview: Language
-Many species use physical and behavioral signals to engage in communication, the transmission of information between individuals. -Humans may be alone in communicating via language. -Speakers of a language all understand the same set of rules, or grammar; language allows us to assemble and share information on any topic
Other symptoms of aphasia
-Neologisms: entirely novel nonsense words. May be generated via insertion or substitution of phonemes (ex: bamama instead of banana) -Nonfluent speech: talking with considerable effort, in short sentences, and without the usual melodic character of conversational speech
Nonhuman communication
-Nonhuman animals such as dogs can learn words and phrases but seem to lack grammar. -Many species are capable of vocal learning and use vocalizations to help form social bonds and identify individuals. -Similarities between birdsong learning and human language development suggest convergent evolution
Collosal Agenesis
-One in 4000 people is born either partially or totally lacking a corpus callosum -They generally lack the neuropsychological limitations of surgical split-brain patients. -The developing nervous system compensates for the absence of the main connection between the hemispheres -activity of two hemispheres has some coordination but in general: seizures, feeding problems, delayed motor skills, cognitive deficits
fluent aphasia
-Patients have difficulty understanding what they read or hear • Word deafness indicates damage to the superior temporal lobe and its connections to the auditory cortex. • Word blindness may suggest significant destruction of the angular gyrus. • Anomia—inability to name persons or objects
Steps of listening
-Sound analysis: turning sounds into phonemes and syllables -Word identification: recognizing words we know -Grammar: identifying nouns, verbs, and phrases -Semantics: accessing network of meanings -Discourse: how do meanings relate to previous ones in the conversation? Purposes: what is speaker's goal, and what does it mean?
Testing a split brain individual
-Sperry's studies tested language function in each hemisphere of split-brain individuals. -Words presented to either visual field showed language ability only if the information reached the left hemisphere. -The right hemisphere is specialized for processing emotional tone of language, controlling attention, and spatial processing, including face perception.
Reorganization
-The nervous system has potential for plasticity and recovery: damaged neurons can regrow connections through collateral sprouting, and adult brains can produce new neurons (neurogenesis), but this is very limited. -Embryonic stem cells show promise for brain repair. -These cells have been shown to reduce symptoms of Parkinson's disease and stroke
Lexicon
-a vocabulary -a given language's word bank
conduction aphasia
-an impairment in the ability to correctly repeat words -Lesions of arcuate fasciculus axons, but not Broca's or Wernicke's, may produce conduction aphasia
Developmental dyslexia
-appears to be a problem in connecting reading with the brain systems for speech, and not a general cognitive deficit. -Brains of individuals with dyslexia show unusual arrangements of cortical cells. • Micropolygyria—small regions of excessive number of gyri • Ectopias—clusters of cells in unusual places
Critics of nonhuman communication
-argue that apes' use of non-vocal forms of language is actually imitation, perhaps cued unconsciously by the experimenter. -However, it seems likely that the linguistic capacity of apes has been underestimated. -Kanzi (a bonobo) learned to use symbols in novel ways through observational learning rather than through intense training
Verbal abilities
-associated with the left hemisphere of the brain; the right hemisphere plays a role in spatial cognition.
Perfect pitch
-associated with the left hemisphere. -Measurements of the left planum temporale are largest in musicians with perfect pitch and smallest in nonmusicians
dichotic presentation
-delivers different stimuli to each ear at the same time -Right-handed persons identify verbal stimuli delivered to the right ear more accurately than verbal stimuli delivered to the left—a right ear advantage. -50% of left-handed individuals have a left- ear advantage
Corpus callosum
-dense fiber tract located beneath the folds of the cortex -anterior region: genu -middle: body -posterior region: splenium -average length of a callosal fiber in humans is 175 mm. It takes almost 30ms to signal that length a fiber. -Leads more to independent specialized parallel processing in each hemisphere rather than extensive communication back and forth the callosum
Wada test
-determines involvement of hemispheres in language by anesthetizing each hemisphere separately; simulates a stroke in one hemisphere. -Confirms that most people have left- hemisphere specialization for language, regardless of handedness. -Rarely, language is lateralized to the right hemisphere; these individuals are usually left-handed
Nonhuman primates
-display a wide range of vocalizations. -Sounds may be used for social connections, to signal readiness to mate, or to alert others to danger or territory. -Most nonhuman primate vocalizations have a preprogrammed quality; suggests they are genetically determined -Chimpanzees and gorillas can learn other systems of communication: American Sign Language (ASL) Use of arbitrary colored tokens or computerized symbols in ways that seem to reflect an acquired ability to form short "sentences"—novel, meaningful chains made up of basic units of meaning
semantic network
-ex: transportation, car, street, ambulance, truck--> firetruck, fire, heat -after stroke see semantic paraphasia: replacing words within the same semantic network
Lateralization
-hemisphere specialization -ex: language (left lateralization) -No evidence supports notions that personality traits or strengths, such as being creative or analytical, are linked to one hemisphere or the other
Aphasia
-impairment in language ability caused by brain injury -90-95% of aphasia cases result from damage to the left cerebral hemisphere -Less severe damage to left hemisphere may cause paraphasia
fusiform gyrus
-junction between temporal and occipital lobe -active during discrimination of objects -fusiform face area
Motor theory of language
-language zones are motor control systems, involved in both the production and perception of the complex motions that produce speech. -The same language-related regions of the left hemisphere are employed during spoken and sign language. Mirror neurons may be involved. -After left-hemisphere damage, similar aphasia occurs in deaf signers
The right ear advantage
-may reflect the left hemisphere's specialization for language. -This advantage is only evident in simultaneous presentations and is restricted to consonants -ex: ma and pa are presented at the same time, info to right gets processed in the left hemisphere first (contralateral processing) --> right ear advantage, most people have
Language
-meaning, culturally informed • Communication through words or symbols for words
Constraint-induced movement therapy (CIMT)
-movement of the "good" limb is prevented to force use of the affected limb -Rehabilitation and retraining can restore some functions after brain or spinal cord injury. -Two weeks of this therapy has been reported by many to restore up to 75% of normal use in the affected limb
Critique of the Wernicke-Geschwind model
-oversimplifies the neural mechanisms of language and prematurely attached functional labels to anatomical findings. -Modern studies show that the arcuate fasciculus—long believed to connect Wernicke's to Broca's area—actually terminates in the precentral gyrus (motor cortex) (before broca'a area)
Evolution of language
-perhaps built on a system originally controlling gestures of the face and hands. -Today, hand movements facilitate speech; deaf signers use the same part of the brain that hearing people use in speaking; people blind from birth use hand gestures while speaking. -These and other studies hint of an ancient association between gestures and speech
Recovery of function
-recovery of behavioral capacity—can occur following brain damage. -Many people who develop aphasia will recover some language abilities. -Recovery from brain damage is better after trauma than after a stroke. -Children recover much faster than adults -trends show better recovery in Broca's aphasia than wernicke's aphasia
Heimispherectomy
-removal of an entire brain hemisphere to save the life of a child born with severe epilepsy. -Produces other severe symptoms: • Complete paralysis of one side • Speech loss • Visual impairments -If performed early enough, the child may recover completely
Brain mapping
-researchers study the language network using functional imaging and electrical stimulation of discrete cortex areas -Stimulation of cortex in patients about to undergo brain surgery resulted in a map of language-related zones of the left hemisphere
Wada test results
-temporary blockage/shut down of cerebral hemisphere -left handed people: majority have language lateralized to the left hemisphere, also likely could have language lateralized to the right or both -right handed people never really have language on both and rarely on the right
Surface dyslexia
-the person attends only to the fine details of reading—which letter makes which sound -Individuals with surface dyslexia find it difficult to recognize words in which the letter-to-sound rules are irregular. -Surface dyslexia does not occur in native speakers of languages that are perfectly phonetic (such as Italian).
global aphasia
-total or near-total total loss of ability to understand language or to speak, read, or write. -Results from large left-hemisphere lesions, affecting all language zones. -Prognosis for language recovery is poor
Split brain operation
-treatment for intractable epilepsy -prevents seizures from spreading from one side to the other -both of hemispheres still working just not communicating
Behavioral and imaging techniques
=demonstrate a right-hemisphere advantage in processing spatial stimuli: Faces, geometric shapes and relations, direction and navigation, 3D rotation of imaginary objects. -Right hemisphere lesions—especially posterior temporal and parietal lobes— produce related symptoms
Planum temporale
=the superior surface of the temporal lobe—is larger in the left hemisphere in most brains. Includes part of Wernicke's area, crucial for speech. -Left and right auditory cortical areas play different roles -This asymmetry is evident even before substantial experience with speech -May be symmetric in schizophrenia or dyslexia--> less lateralization
fMRi in dyslexia
Indicates differences in brain activity in dyslexia: -Compared with controls, people with dyslexia show diminished activation of left posterior regions including the superior temporal lobe and angular gyrus. -Changes in fine structure of the temporo- parietal white matter pathways in adults with dyslexia suggest problems with axonal connections between language areas.
Transcranial magnetic stimulation (TMS)
TMS has shown: -Speech production is associated with activation of face areas and hand areas in the motor cortex. -Speech perception activates specific regions involved with speech production. -Broca's area has functional subregions.
Deep dyslexia
an acquired dyslexia in which a person reads a word as another semantically related word.
agnosia
an inability to identify items such as different kinds of cars or species of birds
Speaking
as a motor act: involving vocal tract, breathing, and motor movements of mouth
Phonemes
basic speech sounds
Acquired dyslexia (alexia)
can occur in adults after injury to the left hemisphere
Fluent (Wernicke's) aphasia
complex verbal output with many paraphasias (sound and/or word substitutions) that make speech unintelligible
Pragmatics
context in which a speech sound is uttered
Dyslexia
difficulty with reading due to developmental or neurological causes
prosody
emotional tone-of-voice aspects
Ex of Silbo Gomero
ex: is a whistled language of the Canary Islands, used by shepherds to communicate over long distances. -fMRI reveals that silbadores process Silbo using the same left-hemisphere mechanisms used for spoken language. -Nonsilbadore controls process the whistle sounds using completely different regions of the brain. The whistle sounds have no linguistic content for them
prosopagnosia
face blindness, people fail to recognize familiar faces, including their own -Damage to the fusiform gyrus causes complete prosopagnosia -Shutting down the right hemisphere in the Wada test can cause difficulty in recognizing faces, especially recognizing one's own face -may be accompanied by other forms of agnosia
Syntax
grammatical rules for constructing phrases and sentences
Injury to the postcentral gyrus
in the anterior end of the parietal—results in sensory deficits on the opposite side
paraphasia
insertion of incorrect sounds or words
Astereognosis
is the inability to recognize objects by touching and feeling them.
Congenital prosopagnosia
lifelong face blindness not due to brain damage— occurs in about 2.5% of people
Tachistoscope test
linguistic stimuli are briefly presented to left or right visual field -Left hemisphere (right visual field) shows better recognition of words and letters. -Right hemisphere (left visual field) shows better recognition of faces and geometric forms. -Light, hue, and simple patterns are recognized by both hemispheres.
Semantics
meanings of words or sentences
Hemiplegia
paralysis of one side of the body or unilateral weakness (hemiparesis)
Auditory areas of the right hemisphere
play a major role in emotional tone-of-voice aspects (prosody), and in perception of music. -Musical perception is impaired by damage to right hemisphere. -Music activates the right hemisphere more than the left. -Only damage to both hemispheres can abolish music perception.
Wernicke's area
posterior regions of the left superior temporal gyrus and part of adjacent parietal cortex; involved in perception and production of speech
Broca's area
region in the inferior frontal lobe involved in speech production
Morphemes
simple units of meaning
Many patients with aphasia may also show other impairments
• Agraphia—inability to write • Alexia—inability to read • Apraxia—motor impairment in the ability to begin and execute skilled voluntary movements, even though there is no muscle paralysis
Spoken Input: Understanding Speech
• Separate important speech from noise • Divide speech stream into meaningful units o Prosody o Coarticulation o Segmentation • Brain areas involved in speech perception and comprehension
Levels of Language Processing: Listening
• Sound input • Auditory-phonetic analysis • Sentence analysis • Inferring intention