Monday, June 30, 2008
Tarnovsky (1867) proposed in an 80 page paper a comprehensive model for organizing aphasic syndromes. He ?pioneered the notion of separating "the localization of function from the localization of the defect." Kojevnikov (1874) preceded Wernicke in publishing "sensory aphasia" due to left temporal injury. Rodossky (1872)connected deficits of sound articulation and comprehension of speech, and "inner speech" and writing disorders. He also noted the emotional reaction of aphasics to their speech.
Contributions to the study of memory were made by Korsakoff (1890) related to medial temporal lobes by Bekhterev in 1907, 50 years before Scoville and Milner.
Lurian period drew on the reflexology of Bekhterev, and Freud. Luria and his mentor Vygotsky rejected the notion that Pavlovian ideas could explain complex processes such as speech, attention, planning. They based their neuropsychology on the principle that higher functions consist of factors that can be parsed, and that functions could not be localized so much as factors comprising the function?.
Astvatsaturov (MI, 1908) proposed in 1908 that amnesia for nouns in revealed after motor center disturbances while amnesia for verbs is due to Wernicke area lesions."
Saturday, June 28, 2008
The following are taken from articles in Brain and Cognition 40:1999 special issue.
Merians AS et al. Patient with aphasia due to corticobasal degeneration did better pantomiming to command than using an actual tool. This contrasts to apraxic patients with left parietal damage who pantomime worse but do better with actual tool. Authors speculate that apraxia in CBD is due to SMA/convesity/premotor areas not parietal (or putamen). They differentiated convexity premotor and SMA premotor cortices. SMA lesions cause apraxia but it implements internally generated programs (projecting from parietal). The CBD patient did not have that much trouble with internally generated programs.
Jacobs et al. studied the same CBD patient as Merians et al., plus two others and evaluated neuropsychologically extensively. They noted adequate gesture comprehension, poor production, a tendency to gesture better with eyes open than closed, normal tests of memory and other basic neuropsychological tests, impaired learned and novel gesture production, impaired gesture imitation. Cortical sensory loss may be important. The network responsible may include the CN/PUT, SMA, convexity and inferior parietal lobule.
Saturday, June 7, 2008
Notes: on Japanese language. In Japanese, one can reverse the word order (OSV= object-subject-verb or SOV) and unlike English, does not change the meaning to passive. A case particle is always placed after a nominal (subject or object) and in Japanese the case particle denotes the role of each word (subject or object). (Japanese is termed an "agglutinative" language).
Various theories exist about gradations of syntactic damage in aphasics and aphasia types. The Japanese language model for studying aphasics allows, for example, one to "control" for abnormal comprehension due to word order because word order does not affect comprehension. Fujita et al. (Jap J Jogoped Phoniatr 18:6-13, Japanese & Communic Disorders Res 6:151-161 in Japanese) proposed aphasics could be classified into 4 groups based on strategies of sentence comprehension, namely, 1) not decoding sentences at all 2) decoding by semantic constraint, 3) decoding by word order and 4) decoding by case particles.
The authors examined whether Japanese aphasics sensitivity to comprehension due to imbedded functors were due to the sentence types in which the functors were embedded, due to informational value and whether different aphasic types had different sensitivity to functors.
The task was in 64 sentence with various factors (inverted word order, not inverted, active, passive ) truth was assessed re pictorial accompanying. 42 aphasics and ten controls were run. Broca's patients had difficulty with truth decisions and could do so only with lexical meanings, ignoring syntactice structure. They had severe trouble with detecting incorrect functors. All aphasics had trouble with reversibility, that is they did worse with nonreversible than reversible sentences. Therefore all apahsics, Brocas plus Wernickes had trouble with functors.
Yamadori A, Ikumura G. Cortex 1975; 11:73-82.
Notes on Japanese language: the basic unit of Japanese similar to a syllable is called a haku. All haku (unlike syllables) have equal temporal duration. A kanji can have any number of haku, but a kana always has one haku. There are 46 kana characters for 46 basic haku. Using diacritical marks all 112 kana can be transcribed with 46 kana. Word length is proportional to the number of haku.
The patient had fluent speech and good understanding but had verbal paraphasias and anomias. Repetition was poor. Written comprehension was good in silent reading but worse in aloud reading. Copying words and sentences was without error.
Repetition was worse with increasing number of syllables. Naming was worse with increasing number of syllables. Cueing did not help. Kana was read better than kanji (but recall that kana only has one haku and so word length was shorter). In writing, word length was an issue with more errors with longer words. That the patient had superior transcription of kanji than kana (due to absent phonology when writing) and superior oral reading of kana was expected (kana has less haku).
The authors thought the problem was the stability of the acoustic word image and not in concept (blogger note: a Luria idea). However the author credits Saussure (1916) and Dubois (1964) that conduction aphasia is "an efferent disturbance." The ability to represent a distinct acoustic image is lost in the first phase of the motor encoding process. They criticize the term "conduction" aphasia noting errors of naming, oral reading and dictation. The authors suggest "central" aphasia as used by Goldstein (1948) and Conrad (1948). "anomia has never been considered as an integral part, except by Conrad"
Notes: alternative explanations of conduction aphasia include disconnection of the motor speech area from Wernicke's area (Wernicke; Geschwind; Benson); degradation of the concept formation (Goldstein; Conrad, Hacaen); disturbed receptive function (Lieppmann and Pappenheim, 1915) and disturbed auditory short term memory(Warrington and Shallice).
Benson DF, Sheremata WA, Bouchard R, Segarra JM, Price JM, Geschwind N. Conduction aphasia Arch Neurol 1973; 28: 339-346.
Conrad K. Strukturanalysen birnpathologischer Falle. Zum problem der leitungsaphasie. Dtsc Z Nervenheilk 159:188-228.
Dubois J, Hacaen H, Angelergues R et al. Etude neurolinguistique de l'aphasie de conduction. Neuropsychologia 2:944 (1964).
Geschwind.. disconnection syndromes etc.
Goldstein K. Language and language disturbances New York, Grune and Stratton, 1948.
Sasanuma S , Fujimora O (1971). Selective impairment of phonetic and non-phonetic transcripton of words in Japanese aphasic patients: kana v. kanji in visual recognition and writing. Cortex &: 1-18.
ibid. An analysis of writing errors in Japanese aphasic patients. Kanji v. kana words. Cortex 8:265-282 (1972) note-- see other post.
Warrington EK , Shallice T (1969). The selective impairment of auditory verbal short-term memory Brain 92: 885-896.
Korean has an phonogram (Hangul) /ideogram (Hanja) reading system analagous to kana/kanji in Japanese. Unlike Japanese, the Korean system does not depend nearly as much on ideograms. Also in Japanese, the same ideogram can be read phonologically or according to its meaning, which is not the case in Korean. Authors report a double dissociation as one showed more impairment in Hanjul adn the other showed the opposite. Blogger note: does Korean offer a purer model for dissociation of phonologic and orthographic routes since ideograms cannot be read phonologically? Need to check with Korean contacts.
Monday, June 2, 2008
autoscopy- the impression of seeing one's own body from an elevated and distanced visuospatial persepctive.
depersonalization-- the subjective experience of unreality and detachment from the self
disembodiment-- an experience in which the self is perceived as being outside the body
out of body experience-- a brief subjective episode of disembodiment, with or without autoscopy.
Out of body experience was repeatedly elicited with stimulation of the posterior STG on the RIGHT in a subject in whom electrodes had been placed to suppress tinnitus. Brain activation on PET scanning occurred on the right at the junction of the SMG and the angular gyrus and the STG gyrus /sulcus on the right. There also was activation in the right precuneus and posterior thalamus extending into the superior vermis.
Such patients may have a transient inability to integrate the visual, tactile, proprioceptive and vestibular information that converges at the site. These events occur in near death experiences, in epilepsy, migraine, and by electrical stimulation of the temperoparietal junction on the right side in epileptics.
The authors note the right SMG processes vestibular information for head and body orientation in space. The area may embody an internal map of self-perception.
In contrast, during depersonalization and derealization, metabolic activity occurs in the inferior parietal cortex (area 7B) so that mislocalization in space is a slightly more dorsal lesion. The anterior cingulum usually coactivates with the angular gyrus, and precuneus during reflective self-awareness (Cavanna AE and Trimble MR. The precuneus: a review of its functional analtomy and behavioral correlates. Brain 2006; 129:564-583). Penfield found patients with floating feelings with stimulation of the right temporoparietal junction, and Blanke et al (Nature 2002; 419:269-270) found the stimulation target for autoscopy was more posterior at the occipital side of the angular gyrus. Caloric stimulation can also produce a feeling of detachment from the suroundings in healthy subjects and those with vestibular disorders (Sang FY et al. 2006; JNNP;77:760-766).
Th authors bring up that epileptics with atrophy might have altered brain connections or coactivation of two areas that are normally not coactivated.
This article concludes with a hypothesis that disembodiment is mediated by the coactivation of the small area at the junction of the angular and SMG and STG/sulcus. Activation of the posterior part of the superior temporal cortex with its map of self perception, results in altered self-perception. They aren't sure if this is what happens in near death experiences.
Sunday, June 1, 2008
Chinese of course uses orthographic symbols to represent words. Whereas there is little or no difference in clinical characterisitcs of Brocas/Wernicke's aphasias in Chinese, several debates have emerged due to the nature of the written language.
Chinese words are monosyllabic, often, and simple tone differences may cause homophones to have different meanings. Since tone is processed by the right hemisphere, which hemisphere mediates processing of tone in Chinese, which is connected to meaning? H. Cohen et al. (Neuropsychologia, 1989; 27:241-5) studied Chinese and French Canadian subjects, and found that on dichotic listening tasks, both groups had a right ear superiority for consonant-vowel syllables, and a left ear superiority for non linguistic melodies and triple tones. However, Baudoin-Chial showed that in French subjects there is left hemisphere processing for Chinese consonant words, and right hemisphere processing for Chinese tone words; however among Chinese subjects there was no dominance for either task (J Neurolinguitics 1986; 2: 189-200).
Among Chinese left hemisphere-damaged nonfluent aphasics, a tonal production deficit exists that is "qualitatively and quantitatively equivalent" to an inability to produce consonants (Packard, Brain and Language 29:212-223). With right hemisphere damage, Chinese subjects become aprosodic but maintain tonal defferentiation for words (Hughes CP et al. Arch Neurol , 1983). In other words, when tone has a linguistic meaning, the left hemisphere processes it.
Chinese grammar is not built-in to words that do not have transitivity, inflections for tense, gender or plural markers on nouns. Subject-verb-object word order is like other languages and is maintained in Broca's and Wernicke's aphasics. Reading errors in Wernicke's aphasia include phoneme substitution, tone changes, morphological errors, and neologisms, with global reading errors and no differences based on the complexity of the logogram, part of speech, concreteness. Broca's errors are mostly phonologic or unclassifiable. Action naming is preferntially affected in Broca's aphasics (Tzeng and Chen, 1988, AAN poster).
Reading of orthographs is delayed among patients with Chinese word-form dyslexia or occipital strokes (author, unpublished). They found that activating an orthograph also activated semantically connected lexigraphs in the same orthographic string. In a case of alexia without agraphia, Chinese aphasics read out component radicles of the orthograph and then piece the radicles together into a single orthograph, even though that method is not normally used in reading. Reading stimulus activates similar orthographs (simlar morphologically, semantically, or phonologically).
Homophones can be constructed by putting together two real orthographs, and nonwords by putting together two normally unrelated orthographs. In Broca's, patients read bisyllabic real words better than homophones, while Wernicke's aphasics did not show homophone superiority to nonwords. The author has two potential explanations, see text.
Dysgraphia in Chinese in Broca's aphasics usually consist of visual errors wherein subjects write normal Chinese orthographs with either missing or excessive strokes. This compares to Western language in which errors use acceptable letter constraints, but make errors of compound or multiple letters rather than omission or substitution. Evidence suggest Chinese use all 3 routes, visual, semantic and phonologic.
Studies have shown equivalent, overwhelming left hemisphere dominance for speech in Chinese undergoing WADA tests or stimulation (Hung CC et al. , J Neurolinguistics, 1985: 1: 143-164) and Rapport RL, Tan CT and Whitaker HA, Brain and Lang 1983; 18: 342-366). Studies show a right hemisphere superiority for processing Chinese or Kanji logographs and a left hemisphere superiority for kana or syllabic symbols in Japanese. However, the studies that show a right hemisphere superiority in RECOGNIZING orthographs show a left hemisphere superiority for processing them semantically (semantic decision of relatedness) ( Tzeng OJL et al. 1979, Nature 282: 499-501; and Hossain R et al., Neuropsychologia1989; 27: 7-5-712; CK LEong et al, Brain and Lang, 1985). Crossed aphasia has not been found in higher rates among Chinese patients.
Ondo WG, Satija P. Withdrawal of visual feedback improves micrographia in Parkinson's disease. Mov Disorder 2007; 31: 2130-2131.
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Teulings HL, Contreras-Vidal JL, Stelmach GE, Adler CH. Adaptation of handwriting size under distorted visual feedback in patients with Parkinson's disease and elderly and young controls.
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Van Gemmert AW, Teulings HL, Stelmach GE.Parkinsonian patients reduce their stroke size with increased processing demands.
Beversdorf DQ, Anderson JM, Manning SE, Anderson SL, Nordgren RE, Felopulos GJ, Bauman ML. Brief report: macrographia in high-functioning adults with autism spectrum disorder. J Autism Dev Disord. 2001 Feb;31(1):97-101.
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