People with developmental dyslexia (DD) have been shown to be impaired in tasks that require the processing of multiple visual elements in parallel. It has been suggested that this deficit originates from disturbed visual attentional functions. The parameter-based assessment of visual attention based on Bundesen's () theory of visual attention allows one to identify and quantify the underlying deficits. The present study provides the first groupwise comparison between children with DD (n = 12; mean age 9.84 years) and typically developing children (n = 12; mean age 9.87 years) with regard to intact and disturbed components of visual attention. From the performance on whole- and partial-report tasks, we derived individual parameter estimates of four different parameters: visual processing speed, storage capacity of visual short-term memory (VSTM), laterality of attentional weighting and efficiency of top-down control. Groupwise comparisons revealed that general attentional resources, processing speed and VSTM storage capacity, are impaired in children with DD compared to typically developing children. In contrast, selectivity parameters, laterality of attentional selection and attentional top-down control did not differ between these groups. Relating the current findings to previous results, obtained in highly comparable methodological settings, from single cases of children with DD, and from a group of adults with DD, we conclude that slowed perceptual processing speed is a primary visual attentional deficit in DD. Furthermore, reduced VSTM storage capacity seems to modulate the difficulties in written language processing imposed by the disorder.
Several lines of evidence suggest that during processing of events, the features of these events become connected via episodic bindings. Such bindings have been demonstrated for a large number of visual and auditory stimulus features, like color and orientation, or pitch and loudness. Importantly, most visual and auditory events typically also involve temporal features, like onset time or duration. So far, however, whether temporal stimulus features are also bound into event representations has never been tested directly. The aim of the present study was to investigate possible binding between stimulus duration and other features of auditory events. In Experiment 1, participants had to respond with two keys to a low or high pitch sinus tone. Critically, the tones were presented with two different presentation durations. Sequential analysis of RT data indicated binding of stimulus duration into the event representation: at pitch repetitions, performance was better when both pitch and duration repeated, relative to when only pitch repeated and duration switched. This finding was replicated with loudness as relevant stimulus feature in Experiment 2. In sum, the results demonstrate that temporal features are bound into auditory event representations. This finding is an important advancement for binding theory in general, and raises several new questions for future research.
Re-encountering a stimulus retrieves nominally relevant, categorical response features related to previous action decisions in response to this stimulus. Whether binding and retrieval extend to nominally irrelevant, metric features relating to an actual body movement is unknown, however. In two experiments, we thus tested whether repeating target or distractor stimuli across trials retrieves the irrelevant duration of spatial responses to these stimuli. We found subtle indication of such retrieval by task-relevant target stimuli, suggesting that binding and retrieval also operate on metric features of a motor response. In contrast, there was no sign of binding and retrieval of metric features for distractor stimuli. We discuss these observations regarding the representation of action episodes during action-related decision making and during actual movement initiation and control.
There is an ongoing debate whether an impairment of visual attentional functions constitutes an additional or even an isolated deficit of developmental dyslexia (DD). Especially performance in tasks that require the processing of multiple visual elements in parallel has been reported to be impaired in DD. We review studies that used parameter-based assessment for identifying and quantifying impaired aspect(s) of visual attention that underlie this multi-element processing deficit in DD. These studies used the mathematical framework provided by the “theory of visual attention” (Bundesen, 1990) to derive quantitative measures of general attentional resources and attentional weighting aspects on the basis of behavioral performance in whole- and partial-report tasks. Based on parameter estimates in children and adults with DD, the reviewed studies support a slowed perceptual processing speed as an underlying primary deficit in DD. Moreover, a reduction in visual short term memory storage capacity seems to present a modulating component, contributing to difficulties in written language processing. Furthermore, comparing the spatial distributions of attentional weights in children and adults suggests that having limited reading and writing skills might impair the development of a slight leftward bias, that is typical for unimpaired adult readers.
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