Visual discrimination of shape by humans

Reaction times to tachistoscopic exposure and a card-sorting task are the two methods by which visual discrimination of shape is studied. The results of experiments using both methods tally, i.e. the order of difficulty of the following shapes was: (1) (easiest) circle vs. triangle; (2) circle vs. square; (3) square vs. triangle; (4) (most difficult) triangle vs. diamond. These results are compared with those obtained by Sutherland, using octopus, and it is concluded that it should be possible to establish to what extent the system of visual analysis in humans differs from that postulated for both octopus and rat.     

Neurocognitive outcomes in children with chronic kidney disease: Current findings and contemporary endeavors

Given the rise in chronic kidney disease (CKD) in both children and adults, CKD has recently been targeted as a public health priority. Childhood onset kidney disease is generally a noncurable and progressive condition that leads to kidney failure by early adulthood. Fortunately, improved identification of kidney problems allows for early intervention, which is thought to slow progression toward end-stage renal disease. In addition, medical interventions for pediatric end-stage renal disease have also improved, allowing children to take advantage of lifesaving renal replacement treatments such as dialysis and kidney transplantation. In spite of improvements in identification and treatment, CKD causes both direct and indirect insults to a variety of organ systems. This paper reviews recently published studies pertaining to the neurocognitive and psychosocial impact of CKD on children of various ages and at various stages of kidney failure. Specific attention is focused on summarizing peer reviewed research that describes associations between kidney functioning and cognitive functioning, language acquisition, visual spatial abilities, memory, and executive functioning. In addition, peer reviewed research describing psychosocial outcomes associated with CKD related to academic achievement, social-behavioral functioning, and quality of life are summarized. The authors also identified disease-specific factors that likely mediate neurocognitive outcomes (e.g., anemia, hypertension, cardiovascular) and endorse the importance of continued interdisciplinary research collaborations that will provide a better understanding of the mechanisms responsible for improved neurocognitive functioning after transplantation. The authors conclude this review by describing a multicenter, prospective, longitudinal, National Institutes of Health funded study that is currently examining the developmental outcomes of children with mild to moderate CKD. The authors speculate that the Chronic Kidney Disease in Children Prospective Cohort Study (CKiD) findings will provide additional evidence-based guidance for clinicians and researchers working with children and adolescents with deteriorating kidney function to improve medical and developmental outcomes.     

Fixation identification in centroid versus start-point modes using eye-tracking data

Fixation-identification algorithms, needed for analyses of eye movements, may typically be separated into three categories, viz. (i) velocity-based algorithms, (ii) area-based algorithms, and (iii) dispersion-based algorithms. Dispersion-based algorithms are commonly used but this application introduces some difficulties, one being optimization. Basically, there are two modes to reach this goal of optimization, viz., the start-point mode and the centroid mode. The aim of the present study was to compare and evaluate these two dispersion-based algorithms. Manual inspections were made of 1,400 fixations in each mode. Odds ratios showed that by using the centroid mode for fixation detection, a valid fixation is 2.86 times more likely to be identified than by using the start-point mode. Moreover, the algorithm based on centroid mode dispersion showed a good interpretation speed, accuracy, robustness, and ease of implementation, as well as adequate parameter settings.     

Inattentional blindness for ignored words: Comparison of explicit and implicit memory tasks

Inattentional blindness is described as the failure to perceive a supra-threshold stimulus when attention is directed away from that stimulus. Based on performance on an explicit recognition memory test and concurrent functional imaging data Rees, Russell, Frith, and Driver [Rees, G., Russell, C., Frith, C. D., & Driver, J. (1999). Inattentional blindness versus inattentional amnesia for fixated but ignored words. Science, 286, 2504–2507] reported inattentional blindness for word stimuli that were fixated but ignored. The present study examined both explicit and implicit memory for fixated but ignored words using a selective-attention task in which overlapping picture/word stimuli were presented at fixation. No explicit awareness of the unattended words was apparent on a recognition memory test. Analysis of an implicit memory task, however, indicated that unattended words were perceived at a perceptual level. Thus, the selective-attention task did not result in perfect filtering as suggested by Rees et al. While there was no evidence of conscious perception, subjects were not blind to the implicit perceptual properties of fixated but ignored words.     

Non-lateralised deficits of drawing production in hemispatial neglect

Spatially lateralised deficits that typically define the hemispatial neglect syndrome have been shown to co-occur with other non-lateralised deficits of attention, memory, and drawing. However even a simple graphic task involves multiple planning components, including the specification of drawing start position and drawing direction. In order to investigate the influence of these factors in neglect we presented patients with a circle-copying task, and specified the drawing start point. The ability to draw from the instructed location was strongly related to tests that measure constructional abilities, but not related to start point laterality. In contrast, the direction in which patients drew the circle was affected by start point laterality: patients with neglect were less likely to draw in a typical direction when the cue was on the affected side of space and this was strongly related to severity of the neglect. Patients with neglect consistently produced circles that were smaller than the model; however, the scaling was not affected by the laterality of the start point, nor was the proportion of drawings correctly started at the cue. These findings demonstrate the complex relationship between neglect and even the simplest test for the syndrome.