Language

Language & the BrainLanguage & the Brain

What is Language?What is Language?

A system by which sounds, symbols, and A system by which sounds, symbols, and gestures are used for communicationgestures are used for communication

Sensory/Motor ConvergenceSensory/Motor Convergence Language enters the brain through sensory Language enters the brain through sensory

inputs (vision, hearing – touch?)inputs (vision, hearing – touch?) Produces motor responses Produces motor responses speech, writing speech, writing Processing between sensory and motor Processing between sensory and motor

systems is the essence of languagesystems is the essence of language

For DiscussionFor Discussion

Is language universal in human society?Is language universal in human society? Is language universal among animals?Is language universal among animals? Can animals be taught human language?Can animals be taught human language? How we define language effects our How we define language effects our

answers answers Language = communicationLanguage = communication Language (human) is a complex system that Language (human) is a complex system that

employs predictable rules (grammar)employs predictable rules (grammar)

Animals & LanguageAnimals & Language Many animals use specific vocalizations to Many animals use specific vocalizations to

communicate communicate claim territory, warn of claim territory, warn of danger, attract a matedanger, attract a mate Communication is limited, specific, Communication is limited, specific,

stereotypicalstereotypical Human language is a creative processHuman language is a creative process

The possibilities are effectively endless, The possibilities are effectively endless, limited only by the rules of grammarlimited only by the rules of grammar

Animals & LanguageAnimals & Language

Nim ChimpskyNim Chimpsky WashoeWashoe

Chimps raised in human Chimps raised in human families; taught American sign families; taught American sign languagelanguage

KokoKoko A lowland gorilla, learned more A lowland gorilla, learned more

than 1000 words in American than 1000 words in American sign language and understood at sign language and understood at least 2000least 2000

Demonstrated complex grammar Demonstrated complex grammar useuse

Can animals “learn” human language, or rules of Can animals “learn” human language, or rules of grammar?grammar?

KokoKoko

Historical PerspectiveHistorical Perspective Greek & Roman EmpiresGreek & Roman Empires

Thought that the Thought that the tongue controlled speechtongue controlled speech Sixteenth century: Sixteenth century:

Discovered that speech impairment did not reflect Discovered that speech impairment did not reflect tongue paralysistongue paralysis

Johann Gesner – 1770Johann Gesner – 1770 Inability to associate images or abstract ideas with Inability to associate images or abstract ideas with

their expressive verbal symbolstheir expressive verbal symbols Attributed to brain damage from diseaseAttributed to brain damage from disease Cognitive ability may be intact but verbal expression Cognitive ability may be intact but verbal expression

is lostis lost The first steps toward modern understanding of The first steps toward modern understanding of

aphasiaaphasia

Historical PerspectiveHistorical Perspective

Franz Joseph Gall & phrenologyFranz Joseph Gall & phrenology Speech loss while other mental faculties are retained Speech loss while other mental faculties are retained

suggests that there is a specific brain area devoted to suggests that there is a specific brain area devoted to speechspeech

Jean Baptiste Bouillard – 1825Jean Baptiste Bouillard – 1825 Speech is controlled by the frontal lobesSpeech is controlled by the frontal lobes

Simon Alexandre Aubertin – 1861Simon Alexandre Aubertin – 1861 Described a man who had shot away his frontal bone Described a man who had shot away his frontal bone

in a failed suicide attemptin a failed suicide attempt Pressing a spatula against the exposed brain tissue Pressing a spatula against the exposed brain tissue

halted speech, which resumed immediately when the halted speech, which resumed immediately when the pressure was releasedpressure was released

Broca’s AreaBroca’s Area Paul Broca – 1861Paul Broca – 1861

With Aubertin, examined the brain of a man unable to With Aubertin, examined the brain of a man unable to speakspeak

Found lesion in the frontal lobes Found lesion in the frontal lobes Published a study of 8 similar patients in 1863Published a study of 8 similar patients in 1863

Showed that language expression is controlled by a Showed that language expression is controlled by a portion of the frontal lobe in one hemisphere, usually portion of the frontal lobe in one hemisphere, usually the leftthe left

First clear demonstration that brain function can First clear demonstration that brain function can be localizedbe localized

Now called Broca’s areaNow called Broca’s area

Broca’s AreaBroca’s Area

The Wada ProcedureThe Wada Procedure A simple procedure to study the function A simple procedure to study the function

of a single cerebral hemisphereof a single cerebral hemisphere Fast acting barbiturate is injected into the Fast acting barbiturate is injected into the

carotid artery on one sidecarotid artery on one side Preferentially carried to the ipsilateral Preferentially carried to the ipsilateral

hemispherehemisphere Acts as a short-term anestheticActs as a short-term anesthetic Limbs on the contralateral side become Limbs on the contralateral side become

paralyzedparalyzed Can then assess patients’ ability to Can then assess patients’ ability to

speakspeak If the injection is on the side dominant for If the injection is on the side dominant for

speech, patient is completely unable to talkspeech, patient is completely unable to talk Opposite side retains complete speech abilityOpposite side retains complete speech ability

HandednessHandedness Handedness is an obvious functional asymmetryHandedness is an obvious functional asymmetry 90% of people are right handed90% of people are right handed

Left hemisphere specialized for fine motor controlLeft hemisphere specialized for fine motor control Other species show about equal numbers of left and right Other species show about equal numbers of left and right

handershanders The left hemisphere is dominant in speech in 96% The left hemisphere is dominant in speech in 96%

of right handed people and 70% of left-handed of right handed people and 70% of left-handed people people Thus the left hemisphere is dominant for language in Thus the left hemisphere is dominant for language in

93% of people93% of people Bilateral representation of speech occurs only in left-Bilateral representation of speech occurs only in left-

handershanders

Wernicke’s AreaWernicke’s Area

Karl Wernicke – 1874Karl Wernicke – 1874 Reported that lesions in the left hemisphere in a Reported that lesions in the left hemisphere in a

region distinct from Broca’s area disrupt speechregion distinct from Broca’s area disrupt speech Located on the superior surface of the tempora; Located on the superior surface of the tempora;

lobe between the auditory cortex and the lobe between the auditory cortex and the angular gyrusangular gyrus

Effect of damage to Wernicke’s area is different Effect of damage to Wernicke’s area is different from that associated with Broca’s areafrom that associated with Broca’s area

Broca’s & Wernicke’s Speech CentersBroca’s & Wernicke’s Speech Centers

Borders of both areas are diffuse, not Borders of both areas are diffuse, not clearly definedclearly defined

Areas vary from one person to anotherAreas vary from one person to another Each may be involved in more than one Each may be involved in more than one

language functionlanguage function

Components of the Language SystemComponents of the Language System

AphasiaAphasia

Partial or complete loss of language function Partial or complete loss of language function following brain damagefollowing brain damage

Much of what we know about language and Much of what we know about language and the brain comes from studying patients with the brain comes from studying patients with specific deficitsspecific deficits

The occurrence of distinct types of aphasia The occurrence of distinct types of aphasia suggests that language is processed in suggests that language is processed in several stages at several locations in the several stages at several locations in the brain.brain.

Types of AphasiaTypes of Aphasia

Broca’s AphasiaBroca’s Aphasia Also known as motor or nonfluent aphasiaAlso known as motor or nonfluent aphasia Person has difficulty speaking, although they Person has difficulty speaking, although they

can understand both spoken and written can understand both spoken and written languagelanguage

People with Broca’s aphasia often pause, People with Broca’s aphasia often pause, searching for the right wordsearching for the right word Anomia – inability to find the right wordAnomia – inability to find the right word

Telegraphic speech using only content words Telegraphic speech using only content words agrammatismagrammatism use nouns verbs & adjectivesuse nouns verbs & adjectives omit function words – articles, pronouns conjunctionsomit function words – articles, pronouns conjunctions

Wernicke’s AphasiaWernicke’s Aphasia Clearly different from Broca’s aphasiaClearly different from Broca’s aphasia Speech is fluent but comprehension is poorSpeech is fluent but comprehension is poor Content does not make senseContent does not make sense

Mixtures of clarity & gibberishMixtures of clarity & gibberish More paraphasic errorsMore paraphasic errors

Substitution of incorrect sounds, sound-alike wordsSubstitution of incorrect sounds, sound-alike words Seem undisturbed by their own speechSeem undisturbed by their own speech Comprehension, such as following directions, is Comprehension, such as following directions, is

lostlost Written language, music are similarly affectedWritten language, music are similarly affected

Implication’s of Wernicke’s AphasiaImplication’s of Wernicke’s Aphasia

Wernicke’s area is located on the superior Wernicke’s area is located on the superior temporal gyrus near the primary auditory temporal gyrus near the primary auditory cortexcortex

May play a critical role in relating incoming May play a critical role in relating incoming sounds to their meaningsounds to their meaning

Stores memories of the sounds that make Stores memories of the sounds that make up wordsup words

Wernicke-Geshwind ModelWernicke-Geshwind Model

A model for language processing in the brainA model for language processing in the brain System includes:System includes:

Wernicke’s area Wernicke’s area Broca’s areaBroca’s area The articulate fasiculus The articulate fasiculus

(a bundle of axons connecting the two)(a bundle of axons connecting the two) The angular gyrusThe angular gyrus

Model is an oversimplification, but generally Model is an oversimplification, but generally descriptive of language processingdescriptive of language processing

Repetition of Spoken WordsRepetition of Spoken Words Pathway:Pathway:

Sounds of incoming speech reach the earSounds of incoming speech reach the ear Auditory system processes the soundsAuditory system processes the sounds Neural signals reach the auditory cortexNeural signals reach the auditory cortex

Wernicke-Geshwind model says that sounds are Wernicke-Geshwind model says that sounds are not understood as words until they are not understood as words until they are processed in Wernicke’s areaprocessed in Wernicke’s area

To repeat the words the signal is passed to To repeat the words the signal is passed to Broca’s area via the articulate fasciculousBroca’s area via the articulate fasciculous Broca’s area converts words to code for muscle Broca’s area converts words to code for muscle

movementmovement Sends message to motor cortex for lips, tongue, etc.Sends message to motor cortex for lips, tongue, etc.

Wernicke-Geshwind ModelWernicke-Geshwind ModelRepeating a Spoken WordRepeating a Spoken Word

Reading Written Text AloudReading Written Text Aloud

Incoming information is processed by the Incoming information is processed by the visual systemvisual system Striate cortex & higher-order visual cortical areasStriate cortex & higher-order visual cortical areas

Signals are passed to the angular gyrusSignals are passed to the angular gyrus In the cortex of the angular gyrus, the output In the cortex of the angular gyrus, the output

evokes the same activity as if the words were evokes the same activity as if the words were spokenspoken

Process is now the same as the first exampleProcess is now the same as the first example Wernicke’s area Wernicke’s area Broca’s area Broca’s area motor cortex motor cortex

Wernicke-Geshwind ModelWernicke-Geshwind ModelRepeating a Written WordRepeating a Written Word

Conduction AphasiaConduction Aphasia A lesion disconnects Wernicke’s area from A lesion disconnects Wernicke’s area from

Broca’s area, but leaves both intactBroca’s area, but leaves both intact Usually involves damage to the parietal cortex Usually involves damage to the parietal cortex

and the arcuate fasciculusand the arcuate fasciculus Comprehension is good and speech is Comprehension is good and speech is

fluentfluent Difficulty is in repeating wordsDifficulty is in repeating words

Greatest difficulty with function words, Greatest difficulty with function words, nonsense soundsnonsense sounds

Comprehends sentences they read aloud, Comprehends sentences they read aloud, though spoken words contain errorsthough spoken words contain errors

Aphasia in BilingualsAphasia in Bilinguals If an individual is bilingual, does a stroke If an individual is bilingual, does a stroke

produce aphasia for both languages?produce aphasia for both languages? Depends on order learned and relative fluencyDepends on order learned and relative fluency If languages were learned to same level of If languages were learned to same level of

fluency at about the same time, both are equally fluency at about the same time, both are equally affectedaffected

Language is better preserved in the language Language is better preserved in the language learned more fluently and/or earlier in lifelearned more fluently and/or earlier in life

If learned at different times, one will be affected If learned at different times, one will be affected more than the othermore than the other

Suggests that a second language may use a Suggests that a second language may use a different population of neuronsdifferent population of neurons

Aphasia in the DeafAphasia in the Deaf

Left hemispheric lesions cause a language Left hemispheric lesions cause a language deficit in deaf subjects who use American deficit in deaf subjects who use American Sign Language, similar to verbal aphasicsSign Language, similar to verbal aphasics

Conditions analogous to both Broca’s and Conditions analogous to both Broca’s and Wernicke’s aphasia existWernicke’s aphasia exist

Suggests universality of language Suggests universality of language processing in the brainprocessing in the brain

Model of Language ProcessingModel of Language Processing

Split Brain StudiesSplit Brain Studies

Corpus callosum is severed to treat seizuresCorpus callosum is severed to treat seizures Hemispheres may retain some communication Hemispheres may retain some communication

via the brain stem and smaller commisuresvia the brain stem and smaller commisures No significant impact observed in animal studiesNo significant impact observed in animal studies Humans are differentHumans are different Asymmetry in ability to verbalize answers to Asymmetry in ability to verbalize answers to

questions perceived by the different hemispheresquestions perceived by the different hemispheres Demonstrated by presenting visual stimuli to one Demonstrated by presenting visual stimuli to one

hemispherehemisphere

Visual Stimulation of One HemisphereVisual Stimulation of One Hemisphere

Asymmetrical Visual StimulationAsymmetrical Visual Stimulation Only the right hemisphere sees objects to the Only the right hemisphere sees objects to the

left of the point of fixation and vice versaleft of the point of fixation and vice versa True as long as the eyes can’t move to bring images True as long as the eyes can’t move to bring images

together in the foveatogether in the fovea Pictures or words are flashed for a fraction of a Pictures or words are flashed for a fraction of a

secondsecond Shorter than time needed to move the eyesShorter than time needed to move the eyes

Numbers, words, & pictures presented to the Numbers, words, & pictures presented to the right visual field are repeated/described easily; right visual field are repeated/described easily; on the left they cannot be describedon the left they cannot be described

Objects manipulated with the right hand can be Objects manipulated with the right hand can be described; objects in the left hand cannotdescribed; objects in the left hand cannot

Language on the Right Side of the BrainLanguage on the Right Side of the Brain

Functional AsymmetryFunctional Asymmetry Deficit is speech specific, not language specificDeficit is speech specific, not language specific

Can read and understand letters and numbers with Can read and understand letters and numbers with the right hemisphere if the response is nonverbal.the right hemisphere if the response is nonverbal.

Patient “says” he sees nothing - but successfully picks Patient “says” he sees nothing - but successfully picks matching cardmatching card

Some patients can write with the right Some patients can write with the right hemispherehemisphere

Right brain can understand complex picturesRight brain can understand complex pictures Right brain can be shown to dominate certain Right brain can be shown to dominate certain

tasks such as perspective and complex puzzlestasks such as perspective and complex puzzles The 2 hemispheres can function as independent The 2 hemispheres can function as independent

brains that have different language abilitiesbrains that have different language abilities

Anatomical AsymmetryAnatomical Asymmetry

If function differs, does structure differ between If function differs, does structure differ between the hemispheres?the hemispheres?

Most significant difference is in the Most significant difference is in the planum planum temporaletemporale on the superior surface of the on the superior surface of the temporal lobetemporal lobe Larger on the left side than on the right in about 65% Larger on the left side than on the right in about 65%

of brainsof brains In some cases 5x largerIn some cases 5x larger

Larger even in prenatal development, so not the Larger even in prenatal development, so not the result of useresult of use

Relationship to language asymmetry uncertainRelationship to language asymmetry uncertain

Asymmetry of the Sylvian FissureAsymmetry of the Sylvian Fissure

In most right-handed In most right-handed people, Sylvian people, Sylvian fissure is longer on fissure is longer on the left hemisphere the left hemisphere than on the rightthan on the right

Runs at a more Runs at a more shallow angleshallow angle

Brain Stimulation and LanguageBrain Stimulation and Language

Wilder & PenfieldWilder & Penfield Electrical stimulation at different cortical sites without general Electrical stimulation at different cortical sites without general

anesthesia (patients are conscious)anesthesia (patients are conscious) Stimulation of motor cortex in area that controls mouth Stimulation of motor cortex in area that controls mouth

and lips caused speech arrestand lips caused speech arrest Occurred with stimulation on either side of the brainOccurred with stimulation on either side of the brain

Stimulation of Broca’s area (left hemisphere only)Stimulation of Broca’s area (left hemisphere only) Speech stopped, or with weaker stimulation, was hesitantSpeech stopped, or with weaker stimulation, was hesitant Mild transient anomiaMild transient anomia

Stimulation of 2 other sites also affected speechStimulation of 2 other sites also affected speech In the area of Wernicke’s area and the arcuate fasciculusIn the area of Wernicke’s area and the arcuate fasciculus

Further Electrical Stimulation StudiesFurther Electrical Stimulation Studies George Ojemann - building on Wilder and PenfieldGeorge Ojemann - building on Wilder and Penfield

Stimulation of small parts of the cortex at specific locations Stimulation of small parts of the cortex at specific locations interferes with reading, naming, or repetition of facial interferes with reading, naming, or repetition of facial movementsmovements

Different results are obtained at nearby stimulation sitesDifferent results are obtained at nearby stimulation sites Similar results are obtained at distant sitesSimilar results are obtained at distant sites

Suggests language areas are more complex than Suggests language areas are more complex than Werrnicke-Geshwind modelWerrnicke-Geshwind model Cortical areas other than Broca’s area and Wernicke’s area Cortical areas other than Broca’s area and Wernicke’s area

are involved in languageare involved in language Also the thalamus and striatumAlso the thalamus and striatum Specialized areas may also exist within Wernicke’s and Specialized areas may also exist within Wernicke’s and

Broca’s areasBroca’s areas

PET Imaging of LanguagePET Imaging of Language Researchers studied differences in brain activity between Researchers studied differences in brain activity between

sensory responses to words and production of speechsensory responses to words and production of speech Either listened to words that were read or looked at words Either listened to words that were read or looked at words

flashed on a monitorflashed on a monitor Measured blood flow levels corresponding to the sensory Measured blood flow levels corresponding to the sensory

inputinput Visual stimuli showed increased activity in the striate cortex Visual stimuli showed increased activity in the striate cortex

and extrastriate cortexand extrastriate cortex Did not respond to auditory or visual stimuli that were not Did not respond to auditory or visual stimuli that were not

wordswords Auditory stimuli also showed activity in the primary and Auditory stimuli also showed activity in the primary and

secondary auditory cortexsecondary auditory cortex No increased activity in Wernicke’s area or the angular gyrusNo increased activity in Wernicke’s area or the angular gyrus

PET and Word RepetitionPET and Word Repetition Repetition requires the subject to first see or hear the Repetition requires the subject to first see or hear the

wordword Thus it requires both brain areas for the perceptual Thus it requires both brain areas for the perceptual

process as well as those for speechprocess as well as those for speech To isolate speech, subtracted the components found To isolate speech, subtracted the components found

with the simple sensory task previously describedwith the simple sensory task previously described Speaking words = repeating spoken words - listening to Speaking words = repeating spoken words - listening to

wordswords Shows high activity in the primary motor cortex and Shows high activity in the primary motor cortex and

supplementary motor areasupplementary motor area Also increased activity around Sylvian fissure near Also increased activity around Sylvian fissure near

Broca’s areaBroca’s area Increased activity was bilateralIncreased activity was bilateral

PET and Word ContentPET and Word Content

For each word, subject stated a useFor each word, subject stated a use Cake -> eatCake -> eat Task required thinking and comprehending, as well as Task required thinking and comprehending, as well as

speakingspeaking To isolate verb-noun association, results from just To isolate verb-noun association, results from just

speaking the word were subtractedspeaking the word were subtracted Activated left inferior frontal area, anterior cingulate Activated left inferior frontal area, anterior cingulate

gyrus, and posterior temporal lobegyrus, and posterior temporal lobe Frontal & temporal cortex are thought to be associated Frontal & temporal cortex are thought to be associated

with word association taskwith word association task Cingulate cortex may be related to attentionCingulate cortex may be related to attention

PET IMAGINGPET IMAGING

(a) Listening to (a) Listening to wordswords

(b) Speaking (b) Speaking wordswords

(c) Generating (c) Generating verbsverbs

Conclusions from PET ImagingConclusions from PET Imaging

PET results are consistent with language areas PET results are consistent with language areas determined from studies of aphasiadetermined from studies of aphasia

PET & fMRI studies show similarities in PET & fMRI studies show similarities in processing of spoken language, sign language processing of spoken language, sign language and Brailleand Braille

All studies indicate that language processing All studies indicate that language processing involves complex mechanisms beyond involves complex mechanisms beyond interaction between the 2 major language areasinteraction between the 2 major language areas

This is the subject of ongoing research This is the subject of ongoing research