Incorporating Prediction in Models for Two-Dimensional Smooth Pursuit

A predictive component can contribute to the command signal for smooth pursuit. This is readily demonstrated by the fact that low frequency sinusoidal target motion can be tracked with zero time delay or even with a small lead. The objective of this study was to characterize the predictive contributions to pursuit tracking more precisely by developing analytical models for predictive smooth pursuit. Subjects tracked a small target moving in two dimensions. In the simplest case, the periodic target motion was composed of the sums of two sinusoidal motions (SS), along both the horizontal and the vertical axes. Motions following the same or similar paths, but having a richer spectral composition, were produced by having the target follow the same path but at a constant speed (CS), and by combining the horizontal SS velocity with the vertical CS velocity and vice versa. Several different quantitative models were evaluated. The predictive contribution to the eye tracking command signal could be modeled as a low-pass filtered target acceleration signal with a time delay. This predictive signal, when combined with retinal image velocity at the same time delay, as in classical models for the initiation of pursuit, gave a good fit to the data. The weighting of the predictive acceleration component was different in different experimental conditions, being largest when target motion was simplest, following the SS velocity profiles

Subtle oculomotor difficulties and their relation to motor skill in children with autism spectrum disorder

Objectives Sensorimotor difficulties are often reported in autism spectrum disorders (ASD). Visual and motor skills are linked in that the processing of visual information can help in guiding motor movements. The present study investigated oculomotor skill and its relation to general motor skill in ASD by providing a comprehensive assessment of oculomotor control. Methods Fifty children (25 ASD; 25 typically developing [TD]), aged 7–10 years, completed a motor assessment (comprising fine and gross motor tasks) and oculomotor battery (comprising fixation, smooth pursuit, prosaccade and antisaccade tasks). Results No group differences were found for antisaccade errors, nor saccade latencies in prosaccade and antisaccade tasks, but increased saccade amplitude variability was observed in children with ASD, suggesting a reduced consistency in saccade accuracy. Children with ASD also demonstrated poorer fixation stability than their peers and spent less time in pursuit of a moving target. Motor skill was not correlated with saccade amplitude variability. However, regression analyses revealed that motor skill (and not diagnosis) accounted for variance in fixation performance and fast smooth pursuit. Conclusions The findings highlight the importance of considering oculomotor paradigms to inform the functional impact of neuropathologies in ASD and also assessing the presentation of co-occurring difficulties to further our understanding of ASD. Avenues for future research are suggested

Deciding where to look when there's not much to see

Visually-guided saccades bring items of interest onto the fovea, and have been the subject of intensive study. However, under uncertain visual conditions (e.g., fog, dark, or lack of visual structure), eye movements are guided not only by what is observable in the visual world, but also by prior experience about which locations are likely to provide information or reward. Very little is known about the planning of saccades that are guided by non-visual representations of where to look next. We therefore designed a task in which human subjects searched for a target on either a mean gray screen or a structured noise background (1/f, pink noise). The location of the target in each case did not correspond to any visual element on the screen, but was drawn from a probability distribution with a given center and spread. The subjects were asked to find the target as quickly as possible; an eye movement to the correct location was rewarded with a tone. Eye movements were measured with an ISCAN video-based eye-tracking system. We obtained pilot data from four subjects, including two naive to the purposes of the experiment. Following practice, subjects' eye movements revealed that they had learned both the location of the center of the probability distribution from which the targets were drawn, and information about its spread. Trial duration varied greatly, on average 128ms to 64s, depending on properties of the distribution and probability of the target on each trial. Different eye movement scanning strategies adopted by individual subjects led to differential learning for the pink noise versus the grey background. Subjects seemed to utilize the visual landmarks in the pink noise background despite the fact that they were uncorrelated with target location. We conclude that humans were able to build estimates of where to look even when visual cues did not provide extra information. In addition, our task offers a method for probing how prior information is integrated with visual information

A Review of Serious Games for Children with Autism Spectrum Disorders (ASDs)

This paper reviews 40 serious games designed for children with autism spectrum disorders (ASD) and these games/studies are classified into four categories; technology platform, computer graphics, gaming aspect and user interaction. Moreover, the paper discusses serious games designed for the improvement of communication skills and social behavior, social conversation, imaginative skills, sensory integration and learning accounts in ASD children. The children usually interact with these games by ordinary IO (input/output) e.g. keyboard and mouse or touchscreen tools. Previous researches show the effectiveness of playing serious games on mobiles or tablet devices in helping ASD children to express their feelings and improve the level of engagement with others. However, there are limitations in designing games for helping autistic children with sensory processing disorder (SPD), improving imaginative play, and teaching first aid. Further, there is not much research that addresses repetitive behavior in ASD children