LCS 11: Cognitive Science - Claremont Colleges

Pomona College

LCS 11: Cognitive ScienceReading and the brain

Jesse A. Harris

April 15, 2013

Jesse A. Harris: LCS 11: Cognitive Science, Reading and the brain 1

Agenda

Upcoming talks Presentations

Aim to get data by end of this week Meetings next week Group presentations May 1, 6 & 8

Aphasia Broca Wernicke

Alexia Eye movement basics The brain’s letterbox

Writing response # 4, due Friday April 19


Lorraine TylerThe Neurobiology of Language: Syntax and Semantics

Despite 150 years of study, the properties of the neural languagesystem remain unclear. I will discuss studies involving behaviouraland neuroimaging data on spoken language comprehension.Combining these types of data from healthy people withcomparable data from chronic stroke patients with left hemispherelesions, provides the key ingredients for determining the essentialneural networks in- volved in the syntactic and semantic analysis ofspoken language.

Thursday at 4:15PM, Edmunds 101


William Marslen-WilsonCross-linguistic Contrasts in Morphological Systems: Neurobiological Perspectives

Current research on the neurobiological foundations of humanlanguage suggests that it is mediated by a coalition of twooverlapping systems. A distributed bihemispheric system, largelyshared with our primate relatives, provides a social andinterpretative framework for language comprehension, as well asbasic mechanisms for mapping sounds onto lexical meanings. Aspecialized left hemisphere system, possibly unique to humans,supports core combinatorial functions underpinning morphosyntax.In recent neuroimaging research in English, Polish, and Arabic weinvestigated how diUerent types of morphological process (broadlydeVned as inWectional and derivational) interface with these twosystems, and whether this diUers across languages.

Friday, April 19: 12 noon, Lunch provided, Edmunds 101


Aphasia

AphasiaLanguage disorder produced by braindamage

Damage to speciVc areas associatedwith speciVc types of deVcit.

1. Broca’s (production)

2. Wernicke’s (receptive)

3. Conductive


Broca’s aphasia (1861)

I Leborgne (age 21; single wordword ‘Tam’) and Lelong (age 86;5 words)

I Major speech productiondiXculty

I Other cognitive functions sparedI At autopsy, found lesion in left

frontal lobe

Paul Broca(1824–1880)


Broca’s aphasia

Example of a Broca’s aphasic:http://www.youtube.com/watch?v=f2IiMEbMnPM

Consider watching this clip at home:http://www.youtube.com/watch?v=NUTpel04Nkc

What do you notice about the patient’s speech?


Broca’s aphasia

I Speech is slow and laboredI Utterance are not complexI Almost no “function words” like to, for, the, etc.I Yet, words appear to be meaningful and on-topicI In addition, awareness of deVcit


http://www.youtube.com/watch?v=f2IiMEbMnPM

http://www.youtube.com/watch?v=NUTpel04Nkc

Wernicke’s aphasia (1875)

I Another type of aphasia, termed“sensory aphasia”

I No signs of speech productiondiXculty

I Lack of comprehension, both inthe utterance produced andreception of speech.

I At autopsy, found lesion in leftposterior temporal gyrus.

Carl Wernicke(1848–1905)


Wernicke’s aphasia

Wernicke’s aphasia productionhttp://www.youtube.com/watch?v=aVhYN7NTIKU

Wernicke’s aphasia comprehensionhttp://www.youtube.com/watch?v=dKTdMV6cOZw


Lesion sites

I Broca’s area: left temporal lobe, anterior to primary motorcortex

I Wernicke’s area: Posterior portion of Vrst temporal gyrus

Recap

DeVcit Remainingcapacity

Lesion site

Broca Production,agrammatism

Comprehension,awareness

Frontal lobe

Wernicke Comprehension,Sensicality,Awareness

Speech Wuent Posteriortemporalgyrus

Table: Comparison of aphasia types


http://www.youtube.com/watch?v=aVhYN7NTIKU

http://www.youtube.com/watch?v=dKTdMV6cOZw

Conduction aphasia

I Very rare type of aphasiaI Damage to the arcuate

fasciculus, a neural pathwaythought to connect Wernicke’sarea and Broca’s area (disputed)

I Both comprehension andproduction seem relativelyspared

I DiXculty repeating speechI Make speech errors and try to

correct them, usually with muchdiXculty


Experiments on aphasic patients

Non-reversible sentencesCan utilize our world and semantic knowledge to infer thelikely relations between words.

(3) The book that the girl is reading is yellow

Reversible sentencesRelations between words cannot be determined without helpfrom the syntax.

(4) The horse that the bear is kicking is brown


Experiments on aphasic patientsPredictions

Broca’s If Broca’s aphasics only have a production deVcit forsyntactic processing, they should be able tounderstand complex sentences (just not producethem). Thus, they should be able to perform well onboth reversible and non-reversible sentences.

Wernicke’s Predicted to have across the board diXculty, due toglobal deVcit in comprehension.

Non-reversible Reversible

Wernicke Chance ChanceBroca Good Good

Table: Expectations across diUerent aphasic groups


I Caramazza and Zurif 1976 tested three diUerent kinds ofaphasics, as well as a control

I Presented subjects with reversible and non-reversiblesentences

I From two pictures, asked to pick the appropriatedepiction of the sentence

Non-reversible Reversible

Wernicke Chance ChanceBroca Good Chance

Table: Performance across diUerent aphasic groups


I Evidence that all comprehension capacity for Broca’saphasics is not spared.

I How might we make sense of this pattern? What mightaphasics be doing to process the comprehendnon-reversible sentences that would fail when attemptingto process reversible sentences?


Geschwind’s 1965 model of language processing


Reading

Reading processes involves by various factors, including

1. Acuity limitations on the eye

2. Rapid movements to overcome such limitations

3. Decoding of orthographic forms into phonetic ones

4. Access meaning and integration into sentential anddiscourse context


The eye

RetinaNeural sheet at back ofeye consisting ofphotoreceptors invarious densities.

FoveaHigh concentration ofcones – photoreceptorsresponsible for visualacuity, constituting 15°of visual Veld.


Reading

SaccadeBallistic eye movements that propel the eye to anotherVxation point.

Perceptual spanAsymmetric perceptual window during reading: 3–4 letters toleft; 7–8 to right.


Reading Reading

Alexia

Pure alexiaRecognize letters as letters, butincapable of naming or using them torecognize words.

I Other visual and verbalcapacities are largely spared.

I Able to recognize numbers!I Damage to left occipto-temporal

area Joseph Jules Déjerine(1849–1917)


Dehaene, 2009: Fig 2.1

Dehaene, 2009: Fig 2.1

$ “Why should all human beingshave this built-in facility forreading, when writing is arelatively recent culturalinvention?”

$ “How, then, did the visual wordform area of the human brainarise?”

Oliver Sacks(b. 1933)


$ The brain constrains writingsystems by accepting only alimited types of symbols, thoseshared with other, moreancestral forms of visualprocessing. Thus, shared by allhumans – with natural, anduniversal, restrictions onorthographies.

Stanislas Dehaene(b. 1965)


Writing response 4, due Friday, 19 AprilIn previous classes, we’ve discussed the role of biases incognition. According to Eagleman, biases are, to some extent,what makes us smart by providing some order in perceptualchaos. In the unit on language, we’ve seen examples of bias inword leaning - for example, the whole object bias. In yourresponse, please address the following three questions in 2-3single spaced pages:

(1) Can we say that biases encountered during languageacquisition also make us smart? (2) How about restrictionsthat seem to be imposed by our particular native language -for example, whether we have an exact (cardinal) or relativenumber system? (3) How are such restrictions similar ordiUerent than biases in terms of their cognitive eUect? Defendyour position by using concrete examples of biases andrestrictions from the readings to illustrate your point.

LCS 11: Cognitive Science - Claremont Colleges

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