PubMed · 7800032
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R L Gregory. 1995-01-05. Visual perception. Seeing backwards in time.. https://doi.org/10.1038/373021a0
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Visuo-spatial neglect has long been thought of as a disorder of attention, but a recent experiment shows that, when images from the left side are reflected by a mirror into the 'good' hemispace, neglect patients behave as if the object were behind, or in, the mirror - as if the left side of their world did not 'exist'.
Functional transcranial Doppler sonography (fTCD) is used to measure changes in brain perfusion during different states of brain activity by evaluating flow velocities within the major brain arteries. We developed a computer program called AVERAGE which can be used with various TCD devices and allows for subtle quantitative off-line analysis of Doppler flow signals. AVERAGE supports data transformation, heart beat analysis, noise reduction, trigger signal and marker modification, artifact analysis and artifact rejection, as well as data reduction. Perfusion differences and their time course within two different arteries can be analyzed by parametric and non parametric statistical methods. This is important, for instance, in studies on hemispherical dominance during mental task processing. Each data processing step is supported by graphical output. If investigated bilaterally with interhemispheric analysis even minimal activations can reliably be detected and quantified with a sensitivity known from positron emission tomography approaches.
Five patients with left visual neglect after right hemisphere lesions were examined with a line bisection and a reading task under five different conditions: head and trunk straight ahead, head or trunk oriented 20 degrees to the left and head or trunk oriented 20 degrees to the right. Fixation was always straight ahead. Five patients with right hemisphere lesions but without neglect and five normal subjects served as controls. In all neglect patients, turning the head or trunk to the left reduced line bisection and reading errors significantly as compared with the other three conditions and with the control groups. The modulation of neglect behaviour by trunk as well as head position supports the hypothesis of a disturbed egocentric coordinate system leading to neglect.