Title: Language
1Language
- Chris Rorden
- Aphasia Brocas, Wernickes, etc.
- Alexia
- Anomia
- Dyslexia
- Agraphia
- Split brain patients
- Disconnection syndromes
www.mricro.com
2Background (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.
3Language
- Distinctly human?
- Superior to other animals
- Is there a single anatomical basis?
4Language 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
5Language 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)
6Wernickes prediction
- Predicted two language centers
- Brocas Area speech articulation.
- Wernickes Area language comprehension.
- Predicted 3rd Syndrome
- Disconnection syndrome
- Conduction aphasia
- Damage to arcuate fasciculus
7Conduction 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
8Wernicke-Lichtheim (1885) Schema
- From auditory input (a) to motoric articulation
of speech (m)
Concepts(Distributed)
Brocas Aphasia
Wernickes Aphasia
Conduction aphasia
94 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
106 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
117 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.
12Specifically language
- Aphasics unable to use speech to convey
information. - However, aphasics can often cite memorized texts
- Songs
- Prayers, verses
- Cliché
13Exceptions 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
14Exceptions 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
15Brain 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
16Brocas 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.
17Problems 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?
18Fractionation 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
19Reflections
- 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
20Apraxia 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
21Apraxia 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.
22Wernicke-Lichtheim (1885) Schema
- From auditory input (a) to motoric articulation
of speech (m)
Concepts(Distributed)
Brocas Aphasia
Wernickes Aphasia
Conduction aphasia
23Aphasia Notes lcbr.ss.uci.edu
24Aphasia 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
25Recovery 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.
26Musical 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.
27Reading and writing
- Wernickes aphasics language comprehension
- Regardless whether spoken or written
- Brocas aphasics speech production
- Primarily spoken (except grammar)
- Are there specific reading centres?
28Alexia with agraphia
- Déjerine, 1891 Damage to the angular gyrus (BA
39) leads to - Alexia with agraphia reading writing deficits
- Intact speech comprehension
29Alexia 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
30Reading 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.
31Language 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)
32Brain 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
33Brain 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.
34Corpus 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).
35Split 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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37Alien 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