1/16. Interhemispheric transfer of visual motion information after a posterior callosal lesion: a neuropsychological and fMRI study.Interhemispheric transfer of visual information was investigated behaviourally and with functional magnetic resonance imaging (fMRI) 6 months after a lesion of the posterior two-thirds of the corpus callosum. On tachistoscopical left hemifield presentation, the patient was severely impaired in reading letters, words and geographical names and moderately impaired in naming pictures and colours. In contrast, interhemispheric transfer of visual motion information, tested by verbal report of the direction of short sequences of coherent dot motion presented within the left hemifield, was preserved. The pattern of cerebral activation elicited by apparent motion stimuli was studied with fMRI and compared to that of normal subjects. In normal subjects, apparent motion stimuli, as compared to darkness, activated strongly striate and extrastriate cortex. When presented to one hemifield only, the contralateral calcarine region was activated while regions on the occipital convexity, including putative area V5, were activated bilaterally. A similar activation pattern was found in the patient with a posterior callosal lesion; unilateral left or right hemifield stimulation was accompanied by activation in the contralateral and ipsilateral occipital convexity. Ipsilateral hemifield representation in the extrastriate visual cortex is believed to depend on callosal input. Our observation suggests that this is not the case for visual motion representation and that other, probably parallel, pathways may mediate visual motion transfer after posterior callosotomy.- - - - - - - - - - ranking = 1keywords = behaviour (Clic here for more details about this article) |
2/16. Primary neonatal thalamic haemorrhage and epilepsy with continuous spike-wave during sleep: a longitudinal follow-up of a possible significant relation.epilepsy with continuous spike-waves during sleep was diagnosed in a child who suffered primary neonatal thalamic haemorrhage, and who was followed from birth to 17 years of age. Early cognitive development was normal. Acquired behavioural problems and cognitive stagnation could be directly related to the epilepsy and not to the initial lesion and posthaemorrhagic hydrocephalus. This case and long-term follow-up data on a few children who suffered primary neonatal thalamic haemorrhage suggest that epilepsy with continuous spike-waves during sleep can be a sequel. Disturbances of thalamocortical interactions could play a role in the still poorly understood syndrome of epilepsy with continuous spike-waves during sleep.- - - - - - - - - - ranking = 1keywords = behaviour (Clic here for more details about this article) |
3/16. Two types of auditory neglect.Auditory neglect, defined as inattention to stimuli within the left hemispace, is mostly reported in association with left ear extinction in dichotic listening. However, it remains disputed as to how far dichotic extinction reflects a primary attentional deficit and is thus appropriate for the diagnosis of auditory neglect. We report here on four patients who presented left ear extinction in dichotic listening following right unilateral hemispheric lesions. Auditory spatial attention was assessed with two additional tasks: (i) diotic test by means of interaural time differences (ITDs), simulating bilateral simultaneous spatial presentation of the dichotic tasks without the inconvenience of interaural intensity or content difference; and (ii) sound localization. A hemispatial asymmetry on the ITD diotic test or a spatial bias on sound localization were found to be part of auditory neglect. Two patients (J.C.N. and M.B.) presented a marked hemispatial asymmetry favouring the ipsilesional hemispace in the ITD diotic test, but did not show any spatial bias in sound localization. Two other patients (A.J. and E.S.) had the reverse profile: no hemispatial asymmetry in the ITD diotic test, but a severe spatial bias directed to the ipsilesional side in sound localization. J.C.N. and M.B. had mainly subcortical lesions affecting the basal ganglia. A.J. and E.S. had cortical lesions in the prefrontal, superior temporal and inferior parietal areas. Thus, there are two behaviourally and anatomically distinct types of auditory neglect characterized by: (i) deficit in allocation of auditory spatial attention following lesions centred on basal ganglia; or (ii) distortion of auditory spatial representation following frontotemporoparietal lesions.- - - - - - - - - - ranking = 1keywords = behaviour (Clic here for more details about this article) |
4/16. Acute diquat poisoning with intracerebral bleeding.A case of severe diquat poisoning complicated by the development of aggressive behaviour, oliguric renal failure, and intracerebral bleeding is described. The patient was successfully managed and made a complete recovery. In this paper special attention has been given to the major clinical differences between diquat and paraquat intoxication.- - - - - - - - - - ranking = 1keywords = behaviour (Clic here for more details about this article) |
5/16. Haemorrhage into an arachnoid cyst: a serious complication of minor head trauma.arachnoid cysts are infra-arachnoidal cerebrospinal fluid collections that are usually asymptomatic. However, they can become acutely symptomatic because of haemorrhage and cyst enlargement, which may result from minor head trauma. The range of symptoms is wide and many are "soft" signs. diagnosis is important as cysts causing mass effect require surgery. A case is reported of a child presenting with localised headaches after minor head trauma. Computed tomography demonstrated an arachnoid cyst with evidence of haemorrhage, which required surgical intervention. Other cases of arachnoid cyst presenting to our hospital or reported in the literature are reviewed with respect to presenting symptoms and signs. Localised headaches, behavioural or cognitive changes and ataxia are more commonly associated with this disorder than nausea, vomiting, visual disturbances or seizures. This range of symptomatology following minor head trauma may warrant computed tomography when other criteria for this investigation are not met.- - - - - - - - - - ranking = 1keywords = behaviour (Clic here for more details about this article) |
6/16. Neuropsychological consequences of right thalamic haemorrhage: case study and review.The neuropsychological performance of a right-handed man is examined following haemorrhage from the anterior sections of the right thalamus. A pattern of temporally graded retrograde amnesia, global anterograde amnesia, impaired short-term memory, behavioural changes, and severe executive deficits were identified. The deficits evident in this case are discussed in reference to existing neuropsychological literature regarding the consequences of thalamic infarction. It is proposed that damage to the anterior thalamic nuclei results in a frontal dysexecutive syndrome and that such a dysexecutive syndrome can explain the neuropsychological deficits observed in this case.- - - - - - - - - - ranking = 1keywords = behaviour (Clic here for more details about this article) |
7/16. A new sign of callosal disconnection syndrome: agonistic dyspraxia. A case study.We report a patient with callosal haemorrhage and no extracallosal involvement who developed a unique form of intermanual conflict. In the acute phase the patient showed a mild speech disturbance and right hemiparesis, and in her right hand, a grasp reflex and compulsive manipulation of tools, all attributable to transient frontal involvement. In the chronic phase there was intermanual conflict occasionally associated with the sensation of a second left hand. The patient also presented a sign consisting of compulsive, automatic execution of orders by one hand (the left or the right) when the patient was specifically asked to perform the movement with the other hand (the right or the left, respectively). There was no left-right confusion in this patient. We call this condition agonistic dyspraxia. In contrast with diagonistic dyspraxia, this consists of the agonistic behaviour of the other hand under conditions in which the hand that has been instructed to respond cannot execute the request.- - - - - - - - - - ranking = 1keywords = behaviour (Clic here for more details about this article) |
8/16. Failure of metacontrol: breakdown in behavioural unity after lesion of the corpus callosum and inferomedial frontal lobes.A right-handed man suffered aneurysmal haemorrhage with lesions of the genu and body of the corpus callosum and the inferomedial frontal lobes bilaterally (right more than left). He exhibited remarkable breakdown in behavioural unity characterized by conflict between the two sides of the body, actions inconsistent with verbalizations, and internal conflict over control of the left hand. A major feature of the deficit was its temporal variability. This is interpreted as reflecting intermittent failure of metacontrol processes, which are neural mechanisms for maintaining behavioural unity. Medial frontal structures and their interconnections through the corpus callosum appear particularly important in the maintenance of metacontrol.- - - - - - - - - - ranking = 6keywords = behaviour (Clic here for more details about this article) |
9/16. Dissociated perceptual-sensory and exploratory-motor neglect.A patient with a right sided parietal lobe infarction manifested left sided sensory extinction in the visual, auditory, and tactile modalities but had only mild exploratory-motor neglect. In contrast, another patient with a right frontal haemorrhage demonstrated only left sided exploratory-motor hemispatial neglect. Tasks that combined perceptual and exploratory features elicited varying degrees of neglect in each patient. These two cases with dissociated neglect behaviour lend further evidence for behavioural specialisation within components of a cortical network for directed attention: sensory-representational aspects mediated primarily by the parietal component, motor-exploratory primarily by the frontal component. These cases also highlight the need to include and distinguish among several different measures of neglect in the clinical investigation of patients with hemispatial inattention.- - - - - - - - - - ranking = 2keywords = behaviour (Clic here for more details about this article) |
10/16. The comportmental learning disabilities of early frontal lobe damage.Two adult patients are described who suffered bilateral prefrontal damage early in life and who subsequently came to psychiatric attention because of severely aberrant behaviour. A battery of developmental psychology paradigms (not previously used to assess neurologically impaired individuals) showed that social and moral development of these 2 patients was arrested at an immature stage. In comparison with other types of brain damage which disrupt cognitive development, frontal damage acquired early in life appears to provide the neurological substrate for a special type of learning disability in the realms of insight, foresight, social judgement, empathy, and complex reasoning.- - - - - - - - - - ranking = 1keywords = behaviour (Clic here for more details about this article) |
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