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  • 1
    ISSN: 0942-0940
    Keywords: Cortical dysplasias ; epilepsy ; callosotomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Four patients suffering for severe drug-resistant epilepsy from bihemispheric cortical dysplasias underwent anterior callosotomy. One of these patients also presented mental retardation of mild degree associated with the epileptic syndrome. There were no operative complications in this series. Clinical signs of interhemispheric disconnection were not detectable postoperatively. Twenty-eight to 53 months after surgery, the generalized seizures were completely suppressed in 2 cases, and were reduced by 89–97% in frequency in the other 2 cases. Partial seizures were less affected by callosotomy being reduced by 14–87%. In an additional fifth case of intractable epilepsy from bihemispheric cortical dysplasias with associated severe mental retardation operated upon elsewhere for callosotomy and followed at our institution, the outcome for seizures was completely unsatisfactory. Neurophysiological studies revealed that the interhemispheric transfer (IHT) of visuo-motor responses was functionally impaired after callosotomy only in one patient who harboured bilateral cortical dysplasias in the occipital lobes. This malformation might affect the pattern of axonal projection to the posterior portion of the corpus callosum which is considered of crucial importance for the integration of crossed visuo-motor responses. From this paper the following conclusions can be drawn: a) epileptic patients with severe drug-resistant epilepsy due to bihemispheric cortical dysplasias are good candidates for callosotomy, b) one-stage extensive anterior callosotomy sparing the splenium is the procedure of choice, c) associated severe mental retardation seems to contra-indicate callosotomy, d) the neurophysiological study of the IHT can yield information on the functional status of the corpus callosum.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 13 (2001), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Two patients with corpus callosum resection, one complete and the other sparing the genu and the rostrum, were tested for discrimination of three basic taste stimuli (sour, bitter, salty) applied to the right or left sides of the tongue. Responses were made by pointing with either hand to written words or images of visual objects corresponding to the stimuli, a language-based discrimination. In both patients, response accuracy was significantly above chance for both hemitongues but there was a significant advantage for the left side. Reaction time was shorter for left stimuli than for right stimuli but the difference was not significant. Eight normal controls matched for age with the patients performed equally well with right and left hemitongue stimuli and so did a third callosotomy patient with sparing of the posterior callosum, including the splenium. Tactile and visual tests showed that the left hemisphere was responsible for language-based responses in the first two patients. The results confirm and extend previous findings in another callosotomy patient, indicating that: (i) taste information from either side of the tongue can reach the left hemisphere in the absence of the corpus callosum; (ii) the ipsilateral input from the tongue to the left hemisphere is more potent functionally than the contralateral input and (iii) in the normal brain, the corpus callosum, specifically its posterior part including the splenium, appears to equalize the effects of the ipsilateral and contralateral gustatory inputs on the left hemisphere. Taken together with evidence about lateralized taste deficits following unilateral cortical lesions, the results also suggest that the gustatory pathways from tongue to cortex are bilaterally-distributed with an ipsilateral predominance that may be subject to individual variations.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0028-3932
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Psychology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Neuropsychologia 24 (1986), S. 749-758 
    ISSN: 0028-3932
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Psychology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1106
    Keywords: Visuomotor integration ; Interhemispheric communication ; Callosotomy ; Callosal agenesis ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Normally, simple digital or manual responses to a light stimulus in the right or left visual hemifields are performed faster with uncrossed hand-field combinations than with crossed hand-field combinations. Because of the organization of visual and motor pathways, the integration of uncrossed responses is assumed to occur within a single hemisphere, whereas a time-consuming inter-hemispheric transfer via the corpus callosum is considered to be necessary for the integration of crossed responses. However, callosal transfer may be dispensable for those crossed responses which can be controlled through ipsilaterally descending motor pathways by the hemisphere receiving the visual stimulus. We investigated crossed-uncrossed differences (CUDs) in speed of simple visuomotor responses to lateralized flashes in one subject with total section of the corpus callosum and two subjects with complete callosal agenesis. We recorded the reaction times as well as the premotor times, as indicated by the electromyographic latencies of the prime movers, of three types of responses: a distal response involving a thumb flexion, a proximal response chiefly involving a forearm flexion and an axial response involving a shoulder elevation. Further, the three types of responses to a single lateralised flash were performed both unilaterally and bilaterally. The three acallosal subjects showed CUDs greatly exceeding normal values on distal responses, either unilateral or bilateral, and on unilateral proximal responses. These abnormally long CUDs stood in sharp contrast to the insignificant CUDs exhibited by the same subjects on bilateral proximal responses and on unilateral and bilateral axial responses in agreement with correspondingly insignificant CUDs reported for normal subjects. These results confirm that a callosal contribution is important for the execution of fast distal and unilateral proximal responses to a visual stimulus directed to the hemisphere ipsilateral to the responding hand. By contrast, the other types of crossed responses appear to be efficiently coordinated across the midline without the aid of the corpus callosum. This is in keeping with the hypothesis that they are governed by a bilaterally distributed motor system which is preferentially activated for the execution of symmetrical bilateral movements, employing axial and proximal limb muscles.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1590-3478
    Keywords: Functional MR ; Motor-premotor cortex ; Simple-complex movements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Sommario Scopo di questo studio è stato quello di dimostrare la possibile differenza di attivazione bilaterale per i movimenti delta mano non-dominants nei confronti di quella dominante come pure il diverso coinvolgimento delle aree corticali motorie durante l'esecuzione di movimenti complessi della mano rispetto ai movimenti semplici. È stato utilizzato un apparecchio standard di risonanza magnetica di 1,5 T, per tocalizzare le aree corticali motorie delta mano, utilizzando la tecnica BOLDc ed immagini FLASH a singola sezione. 10 soggetti destrimani sani sono stati utilizzati come volontari per to studio; gli stimoli motori consistevano nell'esecuzione di movimenti semplici (flesso-estensione delle dita) da parte sia delta mano dominante the di quella non dominante, e di movimenti complessi (opposizione delle 4 dita al pollice in maniera ripetuta secondo una sequenza stabilita, 2,4,3,5) da parte delta mano non-dominants. L'esecuzione dei movimenti semplici ha determinato l'attivazione controlaterale dell'area motoria primaria (MA); attivazione ipsilaterale è stata osservata solo per la mano non dominante. Anche l'area supplementare motoria (SMA) è stata attivata, con chiara prevalenza per quella controlaterale. L'entità di attivazione bilaterale delta MA non cambiava con l'esecuzione di movimenti complessi, mentre la SMA, così come l'area premotoria laterale (LPA), erano maggiormente attivate in entrambi i lati con questo tipo di stimolo. In conclusione, la MA ipsilaterale è attivata per movimenti — anche se semplici — eseguiti con la mano non-dominants; esiste una notevole attività funzionale, comprendente la SMA sia controlaterale che ipsilaterale, durante l'esecuzione di movimenti complessi.
    Notes: Abstract The purpose of this study was to show a gradient of possible bilateral activation for movements of the non-dominant vs. dominant hand, as well as for areas involved in complex vs. simple hand movements. A standard 1.5 T magnetic resonance imaging (MRI) system has been utilized to localize the cortical motor hand areas, using the blood oxygen level dependent contrast (BOLDc) technique and single-section fast low-angle shot (FLASH) imaging. Ten normal right-handed subjects volunteered for the study. The motor tasks consisted of simple (flexion-extension) finger movements of either hand, and complex movements (finger-to-thumb opposition in a repeating, pre-planned sequence) of the non-dominant hand. Simple movements caused contralateral activation of the primary motor area (MA); ipsilateral activation was observed for the non-dominant hand only. Supplementary motor area (SMA) was also activated, with a clear contralateral prevalence. The ratio of bilateral activation of MA did not change with complex movements of the non-dominant hand, while SMA as well as lateral premotor area were largely bilaterally activated in this task. In conclusion, the ipsilateral MA is activated for movements — even simple — performed with the non-dominant hand. There is widespread functional activity, involving both contralateral and ipsilateral SMA, for complex movements.
    Type of Medium: Electronic Resource
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