Language And Brain

Language & The Brain

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Broca’s Area

Posterior Speech Areas Including Wernicke’s Area

Dr. Jitendra K Sinha Asst. Prof., AINN

Language Acquisition

Name of Institution

•  Language is human specific •  Critical Period in First Language: –  Acquisition of L1 is impaired after puberty

•  Critical Period in Second Language: –  Acquisition of L2 is impaired after puberty Evolution of Language: –  Gestures were important

Nonhuman Primates

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•  Vocalizations look preprogramed, serving specific purposes only •  Initiated by sub-cortical areas like limbic system •  But for vocalization and decoding, they also use left hemisphere

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Language Disorders

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•  Egyptians reported speech loss after blow to head 3000 years ago •  Broca (1861) finds damage to left inferior frontal region (Broca’s area) of a language impaired patient, in postmortem analysis

Language Disorders (2)

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•  In language disorders –  90-95% of cases, damage is to the left hemisphere –  5-10% of cases, to the right hemisphere

•  Wada test is used to determine the hemispheric dominance –  Sodium amydal is injected to the carotid artery –  First to the left and then to the right

Language Disorders (3)

Name of Institution

•  Paraphasia: –  Substitution of a word by a sound, an incorrect word, or an unintended word

•  Neologism: –  Paraphasia with a completely novel word

•  Nonfluent speech: –  Talking with considerable effort

•  Agraphia: –  Impairment in writing

•  Alexia: –  Disturbances in reading

Three major types of Aphasia

Name of Institution

Rosenzweig: Table 19.1, p. 615

•  Borca’s aphasia –  Nonfluent speech

•  Wernicke’s aphasia –  Fluent speech but unintelligible

•  Global aphasia –  Total loss of language Others: Conduction, Subcortical, Transcortical Motor/Sensory (see also Kandel, Table 59-1)

Brain areas involved in Language

Name of Institution

Wernicke-Geschwind Model Name of Institution

1. Repeating a spoken word

•  Arcuate fasciculus is the bridge from the Wernicke’s area to the Broca’s area

Wernicke-Geschwind Model Name of Institution

2. Repeating a written word

•  Angular gyrus is the gateway from visual cortex to Wernicke’s area •  This is an oversimplification of the issue: –  not all patients show such predicted behavior (Howard, 1997)

Broca’s Aphasia

Brodmann 44, 45 Name of Institution

Dr. Gardner: “Were you in the Coast Guard?” Mr. Ford (patient): “No, er, yes, yes … ship … Massachu … chusetts … Coastguard…years”. He held up his hand twice indicating 19.

Broca’s Area

Gardner H. The Shattered Mind. New York: Vintage Books, 1974, pp 60-61

1.  Language Comprehension (good) Posterior Speech Areas Including Wernicke’s Area

2.  Speech Produc9on (impaired): •  Nonfluent •  Words improperly formed •  Slow and slurred •  Paraphasic errors: “purnpike” (for turnpike)

Wernicke’s Aphasia

Brodmann 22, 30 Name of Institution

Dr. Gardner: “What brings you to the hospital?” I asked the 72year-old retired butcher four weeks after his admission to the hospital.

Broca’s Area

Posterior Speech Areas Including Wernicke’s Area

1.  Language Comprehension (poor) 2.  Speech fluent but nonsensical 3.  Long sentences without meaning

Mr. Gorgan (patient): “Boy, I’m sweating, I’m awful nervous, you know, once in a while I get caught up, I can’t mention the tarripoi, a month agok, quite a little, I’ve done a lot well, I impose a lot, while on the other hand, you know what I mean, I have to run around, look it over, trebbin and all that sort of stuff. Gardner H. The Shattered Mind. New York: Vintage Books, 1974, pp 67-68

THE ARCUATE FASCICULUS

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In 97% of people, both Broca's Area and Wernicke's Area only on leZ hemisphere.

Vernooij, et al. Neuroimage, Vol 35(3) 15 April 2007, pp 1064-1076

White MaPer Tract that connects Broca’s Area and Wernicke’s Area Damage: Conduc9on Aphasia 1. Language Comprehension: intact 2. Fluent speech with some paraphasic errors 3. Inability to repeat words

Name of Institution

The “Arcuate Fasciculus” (lime green) in different primates using tractography.

HUMAN

Nature Neuroscience 11, 426 - 428 (2008)

CHIMPANZEE

MACAQUE

Bilinguals: A Neural Signature?

Name of Institution

Ac9va9on in bilinguals (EnglishSpanish)> monolinguals Contrast for English language (BA 45, Laterial Inferior Parietal Cortex, including Broca’s Area) Hot/red: Ac9va9on unique to bilinguals Spring/green: Shared ac9va9on between bilinguals and monolinguals on a syntac9c task in English.

Adapted from Kovelman, et al. Journal of Cogni9ve Neuroscience January 2008, Vol. 20, No. 1, Pages 153-169

Dyslexia •  •  •  • 

Name of Institution

Problem in learning to read Common in boys and left-handed High IQ, so related with language only Postmortem observation revealed anomalies in the arrangement of cortical cells –  Micropolygyria: excessive cortical folding –  Ectopias: nests of extra cells in unusual location

•  Might have occurred in mid-gestation, during cell migration period

Acquired Dyslexia = Alexia Name of Institution

•  Disorder in adulthood as a result of disease or injury •  Deep dyslexia (pays attn. to wholes): –  “cow” -> “horse”, cannot read abstract words –  Fails to see small differences (do not read each letter) –  Problems with nonsense words

•  Surface dyslexia (pays attn. to details): –  Nonsense words are fine

•  Suggests 2 different systems: –  One focused on the meanings of whole words –  The other on the sounds of words

Lateralization of the Brain

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•  Human body is asymmetrical: heart, liver, use of limbs, etc. •  Functions of the brain become lateralized •  Each hemisphere specialized for particular ways of working •  Split-brain patients are good examples of lateralization of language functions

Lateralization of functions

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(approximate)

•  Left-hemisphere: –  Sequential analysis •  Analytical •  Problem solving

–  Language

•  Right-hemisphere: –  Simultaneous analysis •  Synthetic

–  Visual-Spatial skills •  •  •  • 

Cognitive maps Personal space Facial recognition Drawing

–  Emotional functions •  Recognizing emotions •  Expressing emotions

–  Music

Split-brain

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•  Epileptic activity spread from one hemisphere to the other thru corpus callosum •  Since 1930, such epileptic treated by severing the interhemispheric pathways •  At first no detectible changes (e.g. IQ) •  Animal research revealed deficits: –  Cat with both corpus callosum and optic chiasm severed –  Left-hemisphere could be trained for symbol:reward –  Right-hemisphere could be trained for inverted symbol:reward

Left vs. Right Brain

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•  Pre and post operation studies showed that: –  Selective stimulation of the right and left hemisphere was possible by stimulating different parts of the body (e.g. right/left hand): •  Thus can test the capabilities of each hemisphere

–  Left hemisphere could read and verbally communicate –  Right hemisphere had small linguistic capacity: recognize single words –  Vocabulary and grammar capabilities of right is far less than left –  Only the processes taking place in the left hemisphere could be described verbally

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Videos about Language Processing Genie, the language-deprived child: hPp://www.youtube.com/watch?v=ipt0pjz0mwg hPp://www.youtube.com/watch?v=nha-lGE_wjo hPp://www.youtube.com/watch?v=lxUBkKNOz_k hPp://www.youtube.com/watch?v=IcEEvNFNETM hPp://www.youtube.com/watch?v=rsRr9COItp0 hPp://www.youtube.com/watch?v=3NGUP_JSRic Broca’s aphasia: hPp://www.youtube.com/watch?v=f2IiMEbMnPM Wernicke’s aphasia: hPp://www.youtube.com/watch?v=aVhYN7NTIKU Split-brain pa9ent: hPp://www.youtube.com/watch?v=ZMLzP1VCANo