PubMed · 3242478
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N Buchanan. 1988. Epilepsy and learning.. https://doi.org/10.1111/j.1440-1754.1988.tb01381.x
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Although attention plays a significant role in vision, its spatial deployment and spread in the third dimension is not well understood. In visual search experiments we show that we cannot easily focus attention across isodepth loci unless they are part of a well-formed surface with locally coplanar elements. Yet we can easily spread our attention selectively across well-formed surfaces that span an extreme range of stereoscopic depths. In cueing experiments, we show that this spread of attention is, in part, obligatory. Attentional selectivity is reduced when targets and distractors are coplanar with or rest on a common receding stereoscopic plane. We conclude that attention cannot be efficiently allocated to arbitrary depths and extents in space but is linked to and spreads automatically across perceived surfaces.
Positron emission tomography was used to measure changes in the regional cerebral blood flow of normal people while they searched visual displays for targets defined by color, by motion, or by a conjunction of color and motion. A region in the superior parietal cortex was activated only during the conjunction task, at a location that had previously been shown to be engaged by successive shifts of spatial attention. Correspondingly, the time needed to detect a conjunction target increased with the number of items in the display, which is consistent with the use of a mechanism that successively analyzes each item in the visual field.
This study was designed to confirm the presence of a lateralizing deficit in visual-spatial attention in children with ADHD, to further characterize the nature of this deficit and to specify the likely hemispheric locus of dysfunction. Two versions of the covert orienting of attention procedure which evaluated separately endogenous and exogenous cuing effects were administered to 20 unmedicated children aged 9-12 with ADHD and 20 matched controls. Both groups also underwent thorough psychiatric assessment and testing using the TOVA and the Wisconsin Card Sorting Task (WCST). Children with ADHD showed an asymmetrical performance deficit characterized by a loss of costs on controlled (endogenous) attentional orienting to invalidly cured left visual field targets. The degree of cost asymmetry correlated negatively with the number of categories sorted on the WCST. It was concluded that unmedicated children with ADHD show an asymmetrical performance deficit on the covert orienting procedure characterized by a disruption of right hemispheric attentional mechanisms. This deficit may be related to diminished right hemispheric frontal-striatal catecholamine activity.