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Language

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Language Chris Rorden Aphasia: Broca s, Wernicke s, etc. Alexia Anomia Dyslexia Agraphia Split brain patients Disconnection syndromes www.mricro.com – PowerPoint PPT presentation

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Title: Language


1
Language
  • Chris Rorden
  • Aphasia Brocas, Wernickes, etc.
  • Alexia
  • Anomia
  • Dyslexia
  • Agraphia
  • Split brain patients
  • Disconnection syndromes

www.mricro.com
2
Background (from c82bio)
  • Localization
  • Certain regions devoted to specific tasks.
  • Broca, Gall
  • Based on (almost) no evidence
  • Equipotentiality
  • Whole brain involved with tasks
  • Flourens (1840s), Head, Lashley
  • Both correct/wrong.

3
Language
  • Distinctly human?
  • Superior to other animals
  • Is there a single anatomical basis?

4
Language Production
  • Brocas Area (1861)
  • Difficulty in speech production
  • Loss of ability to repeat speech
  • Comprehension intact
  • Foot of 3rd frontal convolution (BA 44)
  • Left hemisphere (1865)
  • Except left handers

5
Language Comprehension
  • Wernickes Area (1874)
  • Normal production (speech sounds and fluent
    nonsense)
  • Sounds okay if you do not know the patients
    language (e.g. Chinese Wernickes aphasic would
    sound fine to me)
  • Unaware of deficit
  • Impaired comprehension
  • Left hemisphere
  • Superior temporal gyrus(BA 42, 22)

6
Wernickes prediction
  • Predicted two language centers
  • Brocas Area speech articulation.
  • Wernickes Area language comprehension.
  • Predicted 3rd Syndrome
  • Disconnection syndrome
  • Conduction aphasia
  • Damage to arcuate fasciculus

7
Conduction aphasia
  • Can comprehend speech
  • Articulation is intact
  • Difficulty in repeating speech
  • Lesions in Temporal Parietal Junction that knock
    out underlying white matter
  • Patients with damage ONLY to the arcuate
    fasciculus can still generate speech.
  • Why? Other pathways

8
Wernicke-Lichtheim (1885) Schema
  • From auditory input (a) to motoric articulation
    of speech (m)

Concepts(Distributed)
Brocas Aphasia
Wernickes Aphasia
Conduction aphasia
9
4 Transcortical Motor Aphasia
  • Disconnection of Brocas from concepts
  • Speech is slow, terse
  • Can comprehend speech
  • Found after damage to the frontal lobes
  • Unlike Brocas Aphasics, can repeat phrases when
    spoken to
  • direct Wernickes to Brocas pathway intact

10
6 Transcortical Sensory Aphasia
  • Disconnection of Wernickes from concepts
  • Can repeat words
  • Speech is articulate nonsense
  • Unable to comprehend speech
  • Found after damage to the posterior language area

11
7 Pure Word Deafness
  • Loss of ability to understand spoken speech.
  • Normal speech, reading, writing
  • Behaviour and anatomy dissociate from Wernickes
    aphasia
  • Written comprehension intact, intact
    written/verbal production.

12
Specifically language
  • Aphasics unable to use speech to convey
    information.
  • However, aphasics can often cite memorized texts
  • Songs
  • Prayers, verses
  • Cliché

13
Exceptions to the rule
  • Dronkers et al 2000 note exceptions to anatomy
  • Traditional Theory
  • JC will have Brocas and MC will have Wernickes
    Aphasia
  • JH and OB will not have aphasia
  • Reality
  • Neither JC or MC has Aphasia
  • JH has Brocas and OB has Wernickes Aphasia.

Brocas
Wernickes
14
Exceptions to the rule
  • Patients with similar lesions can show very
    different behaviour.
  • What are the implications?
  • Are these exceptions to rule worth worrying
    about?
  • Perhaps we can not see functional extent of
    OB/JHs lesion
  • But JC/MC clearly have damage in areas associated
    with language deficits.
  • Different brains develop differently
  • Group studies required

15
Brain areas vary between people
  • Brocas Area Brodmanns 44/45
  • BA44/45 vary between people
  • Perhaps Broca was right, but JC and JH have
    slightly unusual locations for these regions.
  • Group studies required to resolve this question.

Actual location of BA44/45 based on histology for
two people. Very different size/location (Amunts
et al., 2004 NeuroImage 22, 42-).
Textbook Location of Brocas Area
16
Brocas Aphasia
  • Brocas Aphasia is a syndrome association of
    deficits.
  • Telegraphic speech Produce content words with
    few grammatical markers, pauses between words
  • Apraxia of Speech distortion of speech sounds
    (yawyer instead of lawyer), poor prosody,
    stress on wrong syllable without motor problems
    for non-speech movements.
  • Dysarthria poor control of muscles used in
    articulation
  • Word finding
  • Repetition
  • Comprehension problems with complex grammar.

17
Problems with traditional model
  • Does this cluster of symptoms reflect one
    functional module, or separate anatomical
    neighbours?
  • Comprehension Brocas not simply problem in
    speech production
  • Intact the boy kissed the girl
  • Problems the girl was kissed by the boy
  • Is comprehension specific to speech, or due to
    attentional/working memory problems?

18
Fractionation of Brocas Aphasia
  • Dronkers et al (1994) examined gt 100 aphasics
  • Comprehension deficits associated with Brocas
    Aphasia appear to correlate with Temporal Lobe
    damage.
  • Suggests association due to neighbouring centers,
    not shared function.
  • Finding confirmed in neuroimaging studies
    (Bavelier et al. 1997).

Brocas Area (BA44/45)
Region identified by Dronkers
19
Reflections
  • Dronkers suggests grammatical problems not due to
    Brocas Area
  • Used low quality structural scans
  • See Hillis et al. for critique. Brain (2004),
    127, 1479-1487

20
Apraxia of Speech
  • Dronkers 1996, Nature, 384, 159-161
  • AoS disorder of shaping the vocal tract for a
    particular speech sound.
  • Studied 25 apraxic and 19 control patients.
  • Tested 1 year after lesion deficits are stable.
  • All AoS had damage to portion of insula.
  • This region was spared in all controls.
  • Region near motor strip M1 for mouth.

Apraxics
Controls
21
Apraxia of Speech
  • Dronkers (1996) suggest that insular damage
    causes AoS.
  • Supported by Shuren,, 1993 Donnan et al., 1997
    Bates et al., 2003).
  • Hillis et al. (2004 Brain 127 1479-1487)
    disagree argue Brocas Area critical for AoS.
  • Dronkers examined chronic patients with
    structural scans.
  • Hillis examined acute patients and found that
    patients with AoS had perfusion deficits in
    Brocas Area, even if these were not seen in
    structural scans.

22
Wernicke-Lichtheim (1885) Schema
  • From auditory input (a) to motoric articulation
    of speech (m)

Concepts(Distributed)
Brocas Aphasia
Wernickes Aphasia
Conduction aphasia
23
Aphasia Notes lcbr.ss.uci.edu
 
24
Aphasia notes
  • Anomic problem naming objects
  • Paraphasia use of related but inappropriate
    words
  • Semantic fork when knife is meant
  • Phonemic fork when stork is meant
  • Neologism literally new word, using word that
    bears no obvious relation to a recognizable word.
    e.g., glester
  • Paragrammatic incorrect use of grammatical
    function words. e.g., he is always brillianting

25
Recovery from aphasia
  • Many aphasics get better
  • Is this due to intact tissue on damaged left?
  • Or does right hemisphere take over?
  • Warburton et al. (1999) examined recovered
    aphasics.
  • Many controls show left-only activity far left
  • Others show bilateral activity, but predominantly
    left 2nd from left
  • Patients show different patterns of activity for
    some, intact regions on damaged side have become
    active.

26
Musical Syntax
  • Musical syntax is processed in Broca's area.
  • Non-musicians listen to 5 chords
  • harmonically inappropriate chords generate early
    right-anterior negativity (ERAN), measured with
    MEG.
  • Inferior BA44 source of ERAN (Brocas source and
    right homologue).
  • Maess et al. (2001) Nature Neuroscience 4, 540
    545.

27
Reading and writing
  • Wernickes aphasics language comprehension
  • Regardless whether spoken or written
  • Brocas aphasics speech production
  • Primarily spoken (except grammar)
  • Are there specific reading centres?

28
Alexia with agraphia
  • Déjerine, 1891 Damage to the angular gyrus (BA
    39) leads to
  • Alexia with agraphia reading writing deficits
  • Intact speech comprehension

29
Alexia without agraphia
  • Disconnection of angular gyrus from visual inputs
  • Language outputs intact
  • Patients cannot read
  • Writing preserved
  • Rare left and right pathways to angular gyrus
  • Requires damage to
  • posterior callosum
  • left occipital lobe
  • Without damage to left angular gyrus

30
Reading Vision vs Braille
  • Fusiform gyrus also involved with reading
  • Büchel et al. (1998) Nature, 394, 274-277.
  • 3 Groups
  • Sighted
  • Early Blind
  • Congenitally Blind
  • Reading activates fusiform gyrus (relative to
    speech).
  • Fusiform not simply visual area.

31
Language and laterality
  • Language mainly LEFT hemisphere task
  • Brocas/Wernickes patients left hemisphere
  • Wada Test Intracarotid amobarbital procedure
    temporarily disables one hemisphere
  • Virtually all right handers have language in left
  • Left Handers
  • 70 like right handers
  • 15 language on right (reversed)
  • 15 distributed language (bilateral)

32
Brain asymmetries (Toga Thompson, 2003)
  • Right frontal and left occipital protrude
    relative to counterpart
  • Skull imprints called petalia
  • Cortical structures (sulci) shifted as well
    (Yakovlevian torque)

Cortical Assymetries ? Left occipital wider,
protrudes posteriorly ? Right frontal wider,
protrudes anteriorly
33
Brain asymmetries
  • Sylvian fissure (SF) and superior temporal sulcus
    (STS) also differ between left and right.
  • Left SF/STS more posterior
  • Planum temporale (posterior-ventral face of STS)
    larger on left.
  • See Martins Human Neuropsychology for more
    asymmetries.

34
Corpus callosum
  • Fiber tract between left and right side of the
    brain.
  • 200 million axons
  • Primarily homotopic connects corresponding
    region (Lparietal-Rparietal, Lfrontal-Rfrontal)
  • Also Heterotopic connecting different regions
    (Lfrontal-Rparietal).

35
Split brain patients
  • Complete or partial commissurotomy
  • 1950s operation for intractable epileptics
  • Unseen objects
  • Identified when presented to right hand
  • Verbally unidentified when presented to left
    hand, though hand can select matching object
  • Visual stimuli (briefly flashed)
  • Verbally describe items presented to right field
  • Unable to name items in left field, though can
    choose correct item with left hand
  • Spatial tasks suggest right hemisphere better
    (Nebes, 1978).

36
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37
Alien Hand Syndrome
  • Alien hand syndrome Brion and Jedynak 1972
  • Split brain patients do not recognize their
    unseen left hand when touched by right hand.
  • intramanual conflict e.g. one hand buttons up
    shirt, other unbuttons.
  • Left hand spontaneously engages in actions that
    the patient says they are not intending acts
    foreign, alien or uncooperative.
  • Seen in other patients Goldberg et al (1981)
    report similar effects in patients with
    mesial-frontal/callosal lesions
  • AKA wayward hand, anarchic hand
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