1 Language Chris Rorden Aphasia Brocas Wernickes etc

1 Language • Chris Rorden • • Aphasia: Broca’s, Wernicke’s, etc. Alexia Anomia Dyslexia Agraphia Split brain patients Disconnection syndromes www. mricro. com

2 Background (from c 82 bio) l Localization – – – l Equipotentiality – – l Certain regions devoted to specific tasks. Broca, Gall Based on (almost) no evidence Whole brain involved with tasks Flourens (1840 s), Head, Lashley Both correct/wrong.

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

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

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

6 Wernicke’s prediction l Predicted two language centers: – – l Broca’s Area: speech articulation. Wernicke’s Area: language comprehension. Predicted 3 rd Syndrome: – – – Disconnection syndrome ‘Conduction aphasia’ Damage to arcuate fasciculus

7 Conduction aphasia l l l 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 l From auditory input (a) to motoric articulation of speech (m) Concepts (Distributed) Broca’s Aphasia Wernicke’s Aphasia Conduction aphasia

9 4: Transcortical Motor Aphasia l l l Disconnection of Broca’s from concepts Speech is slow, terse Can comprehend speech Found after damage to the frontal lobes Unlike Broca’s Aphasics, can repeat phrases when spoken to – direct Wernicke’s to Broca’s pathway intact

10 6: Transcortical Sensory Aphasia l l l Disconnection of Wernicke’s 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 l l Loss of ability to understand spoken speech. Normal speech, reading, writing Behaviour and anatomy dissociate from Wernicke’s aphasia Written comprehension intact, intact written/verbal production.

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

13 Exceptions to the rule l l Dronkers et al [2000] note exceptions to anatomy Traditional Theory: – – l JC will have Broca’s and MC will have Wernicke’s Aphasia JH and OB will not have aphasia Reality: – – Neither JC or MC has Aphasia JH has Broca’s and OB has Wernicke’s Aphasia. Broca’s Wernicke’s

14 Exceptions to the rule l Patients with similar lesions can show very different behaviour. l What are the implications? l Are these exceptions to rule worth worrying about? – Perhaps we can not see functional extent of OB/JHs lesion l – – 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 l l Broca’s Area = Brodmann’s 44/45 BA 44/45 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 BA 44/45 based on histology for two people. Very different size/location (Amunts et al. , 2004 Neuro. Image 22, 42 -). Textbook Location of Broca’s Area

16 Broca’s Aphasia l Broca’s 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 nonspeech movements. Dysarthria: poor control of muscles used in articulation Word finding Repetition Comprehension: problems with complex grammar.

17 Problems with traditional model l l Does this cluster of symptoms reflect one functional module, or separate anatomical neighbours? Comprehension: Broca’s not simply problem in speech production – – l 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 Broca’s Aphasia l l Dronkers et al (1994) examined > 100 aphasics Comprehension deficits associated with Broca’s 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). Broca’s Area (BA 44/45) Region identified by Dronkers

19 Reflections Dronkers suggests grammatical problems not due to Broca’s Area l Used low quality structural scans l – See Hillis et al. for critique. Brain (2004), 127, 1479 -1487

20 Apraxia of Speech l l l Dronker’s [1996, Nature, 384, 159 -161] Ao. S: 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 Ao. S had damage to portion of insula. This region was spared in all controls. Region near motor strip [M 1] for mouth. Apraxics Controls

21 Apraxia of Speech l Dronkers (1996) suggest that insular damage causes Ao. S. – l Supported by Shuren, , 1993; Donnan et al. , 1997; Bates et al. , 2003). Hillis et al. (2004; Brain 127 1479 -1487) disagree: argue Broca’s Area critical for Ao. S. – – Dronker’s examined chronic patients with structural scans. Hillis examined acute patients and found that patients with Ao. S had perfusion deficits in Broca’s Area, even if these were not seen in structural scans.

22 Wernicke-Lichtheim (1885) Schema l From auditory input (a) to motoric articulation of speech (m) Concepts (Distributed) Broca’s Aphasia Wernicke’s Aphasia Conduction aphasia

23 Aphasia Notes [lcbr. ss. uci. edu]

24 Aphasia notes l l Anomic: problem naming objects Paraphasia: use of related but inappropriate words – – l l 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 l Many aphasics get better – – l 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 [2 nd from left] Patients show different patterns of activity: for some, intact regions on damaged side have become active.

26 Musical Syntax l l l 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 BA 44 source of ERAN (Broca’s source and right homologue). Maess et al. (2001) Nature Neuroscience 4, 540 – 545.

27 Reading and writing l Wernicke’s aphasics: language comprehension – l Broca’s aphasics: speech production – l Regardless whether spoken or written Primarily spoken (except grammar) Are there specific reading centres?

28 Alexia with agraphia l Déjerine, 1891: Damage to the angular gyrus (BA 39) leads to – – ‘Alexia with agraphia’ reading & writing deficits Intact speech comprehension

29 Alexia without agraphia l 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 1. posterior callosum 2. left occipital lobe Without damage to left angular gyrus

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

31 Language and laterality l Language mainly LEFT hemisphere task – – Broca’s/Wernicke’s patients left hemisphere Wada Test [Intracarotid amobarbital procedure] temporarily disables one hemisphere l l 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) l Right frontal and left occipital protrude relative to counterpart l l 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 l l 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 Martin’s Human Neuropsychology for more asymmetries.

34 Corpus callosum l 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 l Complete or partial commissurotomy – – 1950 s operation for intractable epileptics Unseen objects l l – Visual stimuli (briefly flashed) l l – Identified when presented to right hand Verbally unidentified when presented to left hand, though hand can select matching object 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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37 Alien Hand Syndrome l 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’