Effect of aging on measures of visual attention using dual tasks and visual search

In Canada, as baby boomers age, there will be an increase in the percentage of seniors within the general population (Statistics Canada, 2006). Seniors often have difficulty in performing certain everyday tasks and have greater risk of having health issues. As such, it becomes increasingly important to understand factors that pose difficulty for this group of people. As people get older, many visual functions such as visual acuity, contrast sensitivity, and glare are known to deteriorate (Haegerstrom-Portnoy, 2005). However, when considering activities that aid mobility such as driving and walking, vision related variables are not the only ones that create difficulty for older individuals. A sensory variable such as attention, in conjunction with vision, has been shown in previous studies to be a good predictor of difficulties encountered by the elderly (McGwin, Owsley, & Ball, 1998; Owsley, McGwin, Sloane, Stalvey, & Wells, 2001). Moreover, inattention and distraction seem to be common causes of automobile accidents as well as falls. The work load imposed on the working memory can impact distractibility and inattention. In mobility related activities such as driving and walking, individuals perceive objects that are increasing in size. Experiments were designed to investigate the factors that affect the perception of targets that are enlarging in size. Size matching of expanding targets to a previously presented static target, was investigated in a group of younger participants with normal vision using central or peripheral vision. The results show that size estimates differ depending on whether the target appears in the central visual field or in the periphery. The participants respond faster to targets that appear in the periphery compared to those in the centre/midline. In the subsequent set of experiments we compared the performance of younger and older participants using a dual task paradigm where individuals had to perform two tasks concurrently, one of which was to match the size of an enlarging target. Attention was modulated in the dual tasks by varying the difficulty of the secondary task. It has been found that older individuals have difficulty processing multiple visual tasks or performing multiple tasks in general (Pashler, 1994a, 1994b, 1998; Verhaeghen et al., 2003). Compared to younger individuals, older individuals were found to have greater performance difficulty in the highly demanding dual tasks. These results are compared to those observed in studies of psychological refractory period effects. The differences between the young and older individuals are discussed with respect to limited capacity and bottle neck models of attention. Furthermore, eye movement measures in the dual tasks seem to provide evidence of difficulty in task switching for the older observers. The thesis also investigated the functional field of view of younger and older individuals. By assessing the functional field of view (FFOV) using a method employed earlier by Coeckelbergh et al., (2004a), significant overall age related differences were found. Multiple characteristics of what might affect the FFOV as measured by the attended field of view (AFOV) were also investigated (e.g., impact of a pop out distracter and divided attention). It was found that differences between the two age groups occurred in all conditions. The presence of irrelevant distracters had a greater impact on the older individuals compared to the younger group, whereas divided attention or the presence of the pop out distracter did not affect either age group. Attention processing seemed to be similar for both the younger and older individuals and, therefore, the differences between the age groups appear to be at a quantitative level rather than a qualitative level

A Study of Saccade Dynamics and Adaptation in Athletes and Non Athletes

Purpose: The aim of the study was to delineate differences in saccade characteristics between a population of athletes and non athletes. Aspects specifically investigated were latency, accuracy, peak velocity, and gain adaptation of saccades using both increasing and decreasing paradigms. Methods: A sample of 28 athletes (varsity badminton and squash players) and 18 non athletes (< 3 hour/week in sports) were studied. Eye movements were recorded at 120Hz using a video based eye tracker (ELMAR 2020). Each subject participated in 2 sessions on separate days. Baseline saccade responses to dot stimuli were measured in both sessions (stimulus size: 5-25 deg). The first session involved a gain decreasing paradigm, induced by displacing the stimulus backwards by 3 degrees from the initial target step (12 deg) for 500 trials. In the 2nd session a gain increase was induced by displacing the stimuli by 3 degrees in the forward direction. The latency and accuracy were calculated from the baseline. The asymptotic peak velocity was calculated from the main sequence (amplitude vs. peak velocity). The amplitude gains, calculated from the adaptation phase, were averaged for every 100 saccade responses. The averaged gains were normalized with respect to the baseline, fitted with a 3rd order polynomial, and differentiated to obtain the rate of change. Differences between the groups were compared using a regression analysis. Results: There were no significant differences in latency, accuracy, and asymptotic peak velocity between athletes and non athletes. No significant differences were seen between the two groups in the magnitude of saccadic adaptation, both for decreasing (- 15% in both groups) and increasing (athletes + 7% and non athletes + 5%) paradigms. However, athletes showed a significantly faster rate of adaptation for the gain increasing paradigm (F = 17. 96[3,6]; p = 0. 002). A significant difference was not observed in the rate of adaptation for the gain decreasing adaptation (F = 0. 856[3,6]; p = 0. 512). Conclusions: The study showed that the athletes do not respond better in terms of reaction time or accuracy of saccades. The significant difference in the rate of change of adaptation between the groups shows that online modification of saccades in the positive direction, although not greater in magnitude, occurs quicker in athletes than non athletes

Game play in virtual reality driving simulation involving head-mounted display and comparison to desktop display

This is a post-peer-review, pre-copyedit version of an article published in Virtual Reality. The final authenticated version is available online at: https://doi.org/10.1007/s10055-019-00412-xPrevious studies have reported the effect of driving simulator games on simulator sickness and eye symptoms experienced by users; however, empirical results regarding the game experience using commercial virtual reality head-mounted displays (VR-HMDs) are lacking. We conducted an experiment where participants played a driving simulator game (Live for Speed) displayed through an Oculus Rift DK2 for up to 120 min. Game play duration was recorded. Game experience was surveyed using questionnaires about simulator sickness, eye symptoms, and game engagement. The results showed that the average game play duration for this specific driving simulation game was approximately 50 min. Simulator sickness was negatively correlated with affordable play duration using the VR-HMD. We also found that age was negatively correlated with game play duration. There were no differences between those who did and did not wear frame glasses. In addition, we compared the VR-HMD game play and traditional desktop LCD game play, in terms of simulator sickness, subjective eye symptoms, game engagement, and game performance. The results showed that VR-HMD game play in the driving simulation game was similar to the experience using the desktop LCD display, except for a moderately increased level of simulator sickness. These findings provide new data about VR-HMD’s impact on game play and will inform game designers, players, and researchers for their choices and decisions on proper game duration and the type of devices.This research was supported by Natural Sciences and Engineering Research Council of Canada (NSERC) Grants RPIN-05394 and RGPAS-477166 to BT, and RGPIN-2015-04134 to SC

Time Course of Dichoptic Masking in Normals and Suppression in Amblyopes

Purpose: To better understand the relationship between dichoptic masking in normal vision and suppression in amblyopia we address three questions: First, what is the time course of dichoptic masking in normals and amblyopes? Second, is interocular suppression low-pass or band-pass in its spatial dependence? And third, in the above two regards, is dichoptic masking in normals different from amblyopic suppression? Methods: We measured the dependence of dichoptic masking in normal controls and amblyopes on the temporal duration of presentation under three conditions; monocular (the nontested eye—i.e., dominant eye of normals or nonamblyopic eye of amblyopes, being patched), dichoptic-luminance (the nontested eye seeing a mean luminance—i.e., a DC component) and dichoptic-contrast (the nontested eye seeing high-contrast visual noise). The subject had to detect a letter in the other eye, the contrast of which was varied. Results: We found that threshold elevation relative to the patched condition occurred in both normals and amblyopes when the nontested eye saw either 1/f or band-pass filtered noise, but not just mean luminance (i.e., there was no masking from the DC component that corresponds to a channel responsive to a spatial frequency of 0 cyc/deg); longer presentation of the target (corresponding to lower temporal frequencies) produced greater threshold elevation. Conclusions: Dichoptic masking exhibits similar properties in both subject groups, being low-pass temporally and band-pass spatially, so that masking was greatest at the longest presentation durations and was not greatly affected by mean luminance in the nontested eye

Effect of age and pop out distracter on attended field of view

Purpose: To investigate the functional field of view (FFOV) of younger and older individuals using the attended field of view (AFOV), a method which allows for eye and head movement. The impact of a pop out distracter and a dual task on the FFOV measure was also investigated. Methods: Nine young adult (25 ± 6 years) and 9 older participants (72 ± 4 years) took part in the experiment. The AFOV test involved the binocular detection and localization of a white target (Landolt-C) in a field of 24 white rings (distracters). The further AFOV tests were modified to include the presence of a pop out distracter, a dual task condition, and a combination of the two. Results: Older observers had lower viewing efficiency (log [1/presentation time]) in all conditions (pooled mean across conditions: older: 0.05 ± 0.02; younger: 0.48 ± 0.04) than the younger group. The addition of dual or a pop out distracter did not affect the older group (mean difference ∼104 ± 150 ms and ∼124 ± 122 ms respectively) but the additional pop out distracter reduced the efficiency of the younger group for targets near fixation (mean difference ∼68 ± 35 ms). Conclusion: Better viewing efficiency was observed in younger individuals compared to older individuals. Difficulty in disregarding irrelevant stimuli and thereby resorting to inefficient search strategy is proposed as the reason for the differences. The finding that both older and younger individuals are not affected significantly by the presence of the irrelevant pop out distracter has implications in situations such as driving or hazard avoidance. In such scenarios, search performance is likely not impaired beyond what is found with distracters (visual clutter) in the environment

Binocular treatment of amblyopia using videogames (BRAVO): study protocol for a randomised controlled trial

Amblyopia is a common neurodevelopmental disorder of vision that is characterised by visual impairment in one eye and compromised binocular visual function. Existing evidence-based treatments for children include patching the nonamblyopic eye to encourage use of the amblyopic eye. Currently there are no widely accepted treatments available for adults with amblyopia. The aim of this trial is to assess the efficacy of a new binocular, videogame-based treatment for amblyopia in older children and adults. We hypothesise that binocular treatment will significantly improve amblyopic eye visual acuity relative to placebo treatment.The BRAVO trial is funded by a project grant from the Health Research Council of New Zealand (13/169) and the Hong Kong Health and Medical Research Fund (11122991). Centre for Eye Research Australia receives Operational Infrastructure Support from the Victorian Government