Language

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Language

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

www.mricro.com
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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.

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Language

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

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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

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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)

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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

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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

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Wernicke-Lichtheim (1885) Schema

• From auditory input (a) to motoric articulation
  of speech (m)

Concepts(Distributed)
Brocas Aphasia
Wernickes Aphasia
Conduction aphasia
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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

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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

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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.

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Specifically language

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

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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
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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

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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
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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.

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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?

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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
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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

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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
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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.

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Wernicke-Lichtheim (1885) Schema

• From auditory input (a) to motoric articulation
  of speech (m)

Concepts(Distributed)
Brocas Aphasia
Wernickes Aphasia
Conduction aphasia
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Aphasia Notes lcbr.ss.uci.edu
 
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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

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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.

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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.

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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?

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Alexia with agraphia

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

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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

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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.

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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)

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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
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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.

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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).

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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).

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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