A case study of new assessment and training of unilateral spatial neglect in stroke patients: effect of visual image transformation and visual stimulation by using a head mounted display system (HMD)

<p>Abstract</p> <p>Background</p> <p>Unilateral spatial neglect (USN) is most damaging to an older stroke patient who also has a lower performance in their activities of daily living or those elderly who are still working. The purpose of this study was to understand more accurately pathology of USN using a new HMD system.</p> <p>Methods</p> <p>Two stroke patients (Subject A and B) participated in this study after gaining their informed consent and they all had Left USN as determined by clinical tests. Assessments of USN were performed by using the common clinical test (the line cancellation test) and six special tests by using HMD system in the object-centered coordinates (OC) condition and the egocentric coordinates (EC) condition. OC condition focused the test sheet only by a CCD. EC condition was that CCD can always follow the subject's movement. Moreover, the study focused on the effect of the reduced image condition of real image and the arrows.</p> <p>Results</p> <p>In Patient A who performed the common test and special tests of OC and EC conditions, the results showed that for the line cancellation test under the common condition, both of the percentage of the correct answers at the right and left sides in the test sheet was 100 percent. However, in the OC condition, the percentage of the correct answers at the left side in the test sheet was 44 percent and the right side was 94 percent. In the EC condition, the left side was 61 percent and the right side was 67 percent. In Patient B, according to the result of the use of reduced image condition and the arrows condition by HMD system, these line cancellation scores more increased than the score of the common test.</p> <p>Conclusions</p> <p>The results showed that the assessment of USN using an HMD system may clarify the left neglect area which cannot be easily observed in the clinical evaluation for USN. HMD may be able to produce an artificially versatile environment as compared to the common clinical evaluation and treatment.</p

Blocking Synthesis of the Variant Surface Glycoprotein Coat in Trypanosoma brucei Leads to an Increase in Macrophage Phagocytosis Due to Reduced Clearance of Surface Coat Antibodies

The extracellular bloodstream form parasite Trypanosoma brucei is supremely adapted to escape the host innate and adaptive immune system. Evasion is mediated through an antigenically variable Variant Surface Glycoprotein (VSG) coat, which is recycled at extraordinarily high rates. Blocking VSG synthesis triggers a precytokinesis arrest where stalled cells persist for days in vitro with superficially intact VSG coats, but are rapidly cleared within hours in mice. We therefore investigated the role of VSG synthesis in trypanosome phagocytosis by activated mouse macrophages. T. brucei normally effectively evades macrophages, and induction of VSG RNAi resulted in little change in phagocytosis of the arrested cells. Halting VSG synthesis resulted in stalled cells which swam directionally rather than tumbling, with a significant increase in swim velocity. This is possibly a consequence of increased rigidity of the cells due to a restricted surface coat in the absence of VSG synthesis. However if VSG RNAi was induced in the presence of anti-VSG221 antibodies, phagocytosis increased significantly. Blocking VSG synthesis resulted in reduced clearance of anti-VSG antibodies from the trypanosome surface, possibly as a consequence of the changed motility. This was particularly marked in cells in the G2/ M cell cycle stage, where the half-life of anti-VSG antibody increased from 39.3 ± 4.2 seconds to 99.2 ± 15.9 seconds after induction of VSG RNAi. The rates of internalisation of bulk surface VSG, or endocytic markers like transferrin, tomato lectin or dextran were not significantly affected by the VSG synthesis block. Efficient elimination of anti-VSG-antibody complexes from the trypanosome cell surface is therefore essential for trypanosome evasion of macrophages. These experiments highlight the essentiality of high rates of VSG recycling for the rapid removal of host opsonins from the parasite surface, and identify this process as a key parasite virulence factor during a chronic infection

Attentional competition between modalities: Extinction between touch and vision after right hemisphere damage

The phenomenon of extinction, which occurs frequently after unilateral brain damage, involves a failure to detect the more contralesional of two simultaneously presented stimuli, but with preserved detection of single ipsilesional or contralesional stimuli. Current accounts suggest that the disorder reflects a bias of selective attention, in which ipsilesional stimuli have a competitive advantage. Extinction may be manifested within any one of the major sensory modalities (vision, audition, touch), or it may occur within several modalities in a given individual. Given recent evidence in normals for attentional links between separate sensory modalities, we examined whether extinction can also occur cross-modally, i.e. for double-simultaneous stimuli in separate sensory modalities. We tested whether an ipsilesional event sufficient to extinguish a contralesional stimulus within the same modality may also extinguish a contralesional stimulus in a different modality. Our three patients had right hemisphere damage, and reliable within-modality extinction for visual and tactile stimuli. They also showed significant cross-modal extinction, such that an ipsilesional tactile (or visual) event extinguished awareness of a simultaneous visual (or tactile) event on the contralesional side. These results, which provide the first quantitative evidence for cross-modal extinction, were replicated in a second experiment in which visual and tactile stimuli in the cross-modal conditions were presented at non-homologous elevations within each hemispace. We conclude that after unilateral damage, ipsilesional stimuli have a competitive advantage over contralesional stimuli, and that this affects competition between stimuli from different modalities as well as stimuli within the same modality. These findings are consistent with recent evidence for competitive interactions between tactile and visual events in the control of spatial attention in normals. (C) 1997 Elsevier Science Ltd

Differential production of immune parameters by mouse strains that differ in their susceptibility to Trypanosoma brucei brucei

African trypanosomes are extracellular protozoan haemoparasites causing sleeping sickness to man or nagana to livestock in sub-Saharan Africa. Efforts to control trypanosomiasis have been hampered mainly by the parasites\' ability to constantly undergo antigenic variation. Characterization of immune mechanisms responsible for resistance during trypanosomosis may unravel novel strategies to control the pathogenic consequences of the disease. In the present study, we analyse the severity of infection and immune responses during the acute phase of Trypanosoma b. brucei infection in mouse stains (Balb/c, C57B1/6, C3H/HeNand {Balb/c×C57B1/6} F1 i.e. CB6-F1), that differ in their susceptibility to infection. Mice were intraperitoneally inoculated with 2 Differential productions of immune parameters by mouse strains that differ in their susceptibility to Trypanosoma brucei brucei. Morbidity was quantified by rough coat, reduced activity/movement and anaemia. The kinetics production of plasma level tumor necrosis factor (TNF) and interleukin-4 (IL-4) were evaluated by cytokine-specific sandwich ELISA. Further more, plasma from T.b. brucei-infected mice were tested in antibody-specific ELISAs for variant-specific surface glycoprotein (VSG) reactivity to determine the levels of VSG-specific antibodies. Results showed that T.b. brucei-infected mice differentially produce TNF. Mice (C57B1/6, CB6-FI) that efficiently controlled parasitaemia exhibited significantly higher plasma TNF levels during and after the first peak of parasitaemia than those showing reduced ability to control parasitaemia (C3H/HeN, Balb/c). Furthermore, the production of IL-4 was observed in all mouse strains except for C3H/HeN which exhibited the most susceptible phenotype. Interestingly, infected C3H/HeN mice showed a greatly reduced antibody-searching ability as compared to other strains. Data from this study suggest that resistant in T.b. brucei-infected mice is associated with the production of increased levels of TNF, coupled with low but sufficient le veils of IL-4 and increased antibody levels during the acute phase of infection. The Kenya Veterinarian Vol. 27 2004: pp. 109-11

Prose reading in neglect

Prose reading has been shown to be a very sensitive measure of Unilateral Spatial Neglect. However, little is known about the relationship between prose reading and other measures of neglect and its severity, or between prose reading and single word reading. Thirty participants with a first stroke in the right hemisphere and clear symptoms of spatial neglect in everyday life were assessed with tests of prose reading (text in one column book-like, and in two columns magazine-like), single words reading, and a battery of 13 tests investigating neglect. Seventy percent of these participants omitted words at the beginning of the text (left end), showing Prose Reading Neglect (PRN). The participants showing PRN differed from those not showing PRN only for the overall severity of neglect, and had a lesion centred on the insula, putamen and superior temporal gyrus. Double dissociations emerged between PRN and single word reading neglect, suggesting different cognitive requirements between the two tests: parallel processing in single word reading vs. serial analysis in text reading. Notably, the pattern of neglected text varied dramatically across participants presenting with PRN, including dissociations between reading performance of one and two columns text. Prose reading proved a complex and unique task which should be directly investigated to predict the effects of unilateral neglect. The outcome of this study should also inform clinical assessment and advises given to patients and care-givers