Visual scanning behavior during distracted walking in healthy young adults

Volitional Head Movement Deficits and Alterations in Gait Speed Following Mild Traumatic Brain Injury

OBJECTIVE

Unconstrained head motion is necessary to scan for visual cues during navigation, for minimizing threats, and to allow regulation of balance. Following mild traumatic brain injury (mTBI) people may experience alterations in head movement kinematics, which may be pronounced during gait tasks. Gait speed may also be impacted by the need to turn the head while walking in these individuals. The aim of this study was to examine head kinematics during dynamic gait tasks and the interaction between kinematics and gait speed in people with persistent symptoms after mTBI.

SETTING

A clinical assessment laboratory.

DESIGN

A cross-sectional, matched-cohort study.

PARTICIPANTS

Forty-five individuals with a history of mTBI and 46 age-matched control individuals.

MAIN MEASURES

All participants were tested at a single time point and completed the Functional Gait Assessment (FGA) while wearing a suite of body-mounted inertial measurement units (IMUs). Data collected from the IMUs were gait speed, and peak head rotation speed and amplitude in the yaw and pitch planes during the FGA-1, -3, and -4 tasks.

RESULTS

Participants with mTBI demonstrated significantly slower head rotations in the yaw ( P = .0008) and pitch ( P = .002) planes. They also demonstrated significantly reduced amplitude of yaw plane head rotations ( P < .0001), but not pitch plane head rotations ( P = .84). Participants with mTBI had significantly slower gait speed during normal gait (FGA-1) ( P < .001) and experienced a significantly greater percent decrease in gait speed than healthy controls when walking with yaw plane head rotations (FGA-3) ( P = .02), but not pitch plane head rotations (FGA-4) ( P = .11).

CONCLUSIONS

Participants with mTBI demonstrated smaller amplitudes and slower speeds of yaw plane head rotations and slower speeds of pitch plane head rotations during gait. Additionally, people with mTBI walked slower during normal gait and demonstrated a greater reduction in gait speed while walking with yaw plane head rotations compared with healthy controls.

The effect of mobile phone task and age on gait: A systematic review and meta-analysis

Objective: Mobile phone usage while performing postural-locomotor tasks is everyday activity across persons of all ages in various environmental contexts and health conditions. However, it is also an important factor contributing to accidents. To lower the risk of pedestrian accidents, this meta-analysis aimed to examine how mobile phones affect pedestrian gait and identify how mobile phone tasks and participant age affect gait differently.

Methods: Electronic database searches were performed in The Cochrane Library, PubMed, and Medline. Two examiners evaluated the eligibility and quality of included studies using the Downs and Black checklist. The mean differences (MD) or standardized mean differences (SMD) were calculated for each outcome. Subgroup analyses were used to compare the differential effects of mobile phone task and participant age on gait.

Results: Among 22 eligible studies, 592 participants in 10 countries were analyzed in this meta-analysis. The overall meta-analysis showed that using a mobile phone significantly decreased pedestrian gait velocity (SMD = −1.45; 95% CI: −1.66 to −1.24; p &lt; 0.00001; I2 = 66%), step length (SMD = −1.01; 95% CI: −1.43 to −0.59; p &lt; 0.00001; I2 = 82%), and stride length (SMD = −0.9; 95% CI: −1.19 to −0.60; p &lt; 0.00001; I2 = 79%), significantly increased pedestrian step time (SMD = 0.77; 95% CI: 0.45 to 1.08; p &lt; 0.00001; I2 = 78%), stride time (SMD = 0.87; 95% CI: 0.69 to 1.06; p &lt; 0.00001; I2 = 24%), step width (SMD = 0.79; 95% CI: 0.34 to 1.24; p = 0.0006. I2 = 75%), double support time (SMD = 1.09; 95% CI: 0.86 to 1.31; p &lt; 0.00001; I2 = 42%), and double support (%gait cycle, %GC) (MD = 2.32; 95% CI: 1.75 to 2.88; p &lt; 0.00001; I2 = 26%).

Conclusion: In summary, the effects of mobile phone tasks and participant age on gait were inconsistent. Our study found that resource-intensive tasks (texting and reading) significantly reduced gait velocity, and step time; however, small resource-intensive tasks (calling, talking, and dialing) did not affect these outcomes. In contrast to young adults, step length and step time were not affected by mobile phone use in older adults. Tips: Pedestrians should consider using a mobile phone in their daily lives according to the application scenarios (walking environment, the complexity of mobile phone tasks, pedestrians’ task processing abilities, etc.) as appropriate to avoid dangerous accidents.

Systematic Review Registration: identifier CRD42022358963.

Relationship Between Dual-Task Walking and Level of Conflict Between Gait and Concurrent Tasks in Adolescents

This study aimed to determine the role of resource conflict in dual-task (DT) effects on gait and concurrent tasks in children and adolescents. Gait was evaluated with and without concurrent tasks (visual-manual, visual-vocal and auditory-vocal). The roles of condition (single vs dual) and type of concurrent task in DT effect were tested by Repeated Measured of ANOVA. Relative changes from single to DT conditions were compared using One-Way ANOVA. There were significant reductions in gait speed, cadence, and stride length, and increases in double support time, step time and variability in step time, and no change in variability in stride length, step width, and concurrent task performance from single to DT conditions. DT effects on gait parameters and concurrent tasks were comparable across DT conditions.

The range of visual detection of ground-level cues during distracted walking: Effect of cue contrast and walking speed

Walking while distracted by a smartphone has been a major safety concern for pedestrians. Visual and cognitive attention paid to the smartphone while walking with the head tilted downward would affect the ability to perceive walkway hazards and elevate risks for pedestrian accidents associated with physical contact with obstacles. A laboratory experiment was conducted to evaluate the performance of detecting ground-level visual cues during texting while walking. Forty young smartphone users performed walking trials at faster, preferred, and slower speeds for the dual-task walking on a treadmill and detected approaching cues of three contrast levels. Detection distance was quantified from the location of cue detection to the participants to assess the effects of walking speed and cue contrast on detection performance. Results show that detection distance varied from 1.7 m to 2.9 m for Low to High contrast cues and from 2.3 m to 2.5 m for Slower to Faster walking speeds, and the effects of contrast and speed were statistically significant (p < 0.05). Study findings suggest that higher contrast fixtures or in-ground signals and slower walking would help smartphone users perceive walkway hazards and in-ground safety signals earlier during their distracted walking.

Impact of dual tasking on gaze behaviour and locomotor strategies adopted while circumventing virtual pedestrians during a collision avoidance task

We investigated gaze behaviour and collision avoidance strategies in 16 healthy young individuals walking towards a goal while exposed to virtual pedestrians (VRPs) approaching from different directions (left, middle, right). This locomotor task and an auditory-based cognitive task were performed under single and dual-task conditions. Longer gaze fixation durations were observed on the approaching vs. other VRPs, with longer fixations devoted to the upper trunk and head compared to other body segments. Compared to other pedestrian approaches, the middle pedestrian received longer fixations and elicited faster walking speeds, larger onset distances of trajectory devitation and smaller obstacle clearances. Gaze and locomotor behaviours were similar between single and dual-task conditions but dual-task costs were observed for the cognitive task. The longer gaze fixations on approaching vs. other pedestrians suggest that enhanced visual attention is devoted to pedestrians posing a greater risk of collision. Likewise, longer gaze fixations for the middle pedestrians may be due to the greater collision risk entailed by this condition, and/or to the fact that this pedestrian was positioned in front of the end goal. Longer fixations on approaching VRPs' trunk and head may serve the purpose of anticipating their walking trajectory. Finally, the dual-task effects that were limited to the cognitive task suggest that healthy young adults prioritize the locomotor task and associated acquisition of visual information. The healthy patterns of visuomotor behaviour characterized in this study will serve as a basis for comparison to further understand defective collision avoidance strategies in patient populations.

Peripheral vision in real-world tasks: A systematic review

Peripheral vision is fundamental for many real-world tasks, including walking, driving, and aviation. Nonetheless, there has been no effort to connect these applied literatures to research in peripheral vision in basic vision science or sports science. To close this gap, we analyzed 60 relevant papers, chosen according to objective criteria. Applied research, with its real-world time constraints, complex stimuli, and performance measures, reveals new functions of peripheral vision. Peripheral vision is used to monitor the environment (e.g., road edges, traffic signs, or malfunctioning lights), in ways that differ from basic research. Applied research uncovers new actions that one can perform solely with peripheral vision (e.g., steering a car, climbing stairs). An important use of peripheral vision is that it helps compare the position of one’s body/vehicle to objects in the world. In addition, many real-world tasks require multitasking, and the fact that peripheral vision provides degraded but useful information means that tradeoffs are common in deciding whether to use peripheral vision or move one’s eyes. These tradeoffs are strongly influenced by factors like expertise, age, distraction, emotional state, task importance, and what the observer already knows. These tradeoffs make it hard to infer from eye movements alone what information is gathered from peripheral vision and what tasks we can do without it. Finally, we recommend three ways in which basic, sport, and applied science can benefit each other’s methodology, furthering our understanding of peripheral vision more generally.

Prevalence and dynamics of distracted pedestrian behaviour at railway level crossings: Emerging issues

Recent increases in pedestrian collisions have led to several studies investigating the effects of distraction on pedestrian behaviour at road intersections. Although distraction has been identified as a contributing factor to pedestrian crashes at railway crossings, only limited research is available regarding the prevalence of this behaviour occurring at railway level crossings. It is, therefore, essential to better understand distraction prevalence at railway crossings to support the use of countermeasures to improve safety outcomes. We conducted field observations at a railway crossing in Brisbane, Australia and its adjacent road intersection to gauge the prevalence of distracted pedestrians. Overall, 585 pedestrians were observed and video recorded during the daytime. The video recordings were coded to estimate the prevalence of distraction behaviour that road users engaged in, factors that affected these proportions, and dynamic changes in behaviour. Compliance with signals was also analysed. We found distraction behaviours such as talking and looking at the mobile screen (41.9%) while walking to be prevalent and affected by age. Highly distractive tasks were found to be less commonplace at the railway crossing, accounting for 3% of the observations. Still, pedestrians at the railway crossing engaged in these highly distractive tasks on their phones for a much longer period of time. While most non-compliances (with traffic lights) occurred among attentive pedestrians and are likely to be intentional, non-compliances by distracted pedestrians were also observed, highlighting that distraction can lead to unsafe decisions or lack of decisions that result in unsafe behaviours. Finally, distraction was found to be a dynamic phenomenon as a few pedestrians stopped engaging in distractive tasks once they reached the crossing, while others engaged in more distractive tasks once they were on the road or crossing. Our study shows that pedestrian distraction is a prevalent issue at railway crossings and future research is required to further understand and mitigate this changing behaviour.

Vision, cognition, and walking stability in young adults

Downward gazing is often observed when walking requires guidance. This gaze behavior is thought to promote walking stability through anticipatory stepping control. This study is part of an ongoing effort to investigate whether downward gazing also serves to enhance postural control, which can promote walking stability through a feedback/reactive mechanism. Since gaze behavior alone gives no indication as to what information is gathered and the functions it serves, we aimed to investigate the cognitive demands associated with downward gazing, as they are likely to differ between anticipatory and feedback use of visual input. To do so, we used a novel methodology to compromise walking stability in a manner that could not be resolved through modulation of stepping. Then, using interference methodology and neuroimaging, we tested for (1) interference related to dual tasking, and (2) changes in prefrontal activity. The novel methodology resulted in an increase in the time spent looking at the walking surface. Further, while some dual-task interference was observed, indicating that this gaze behavior is cognitively demanding, several gaze parameters pertaining to downward gazing and prefrontal activity correlated. These correlations revealed that a greater tendency to gaze onto the walking surface was associated with lower PFC activity, as is expected when sensory information is used through highly automatic, and useful, neural circuitry. These results, while not conclusive, do suggest that gazing onto the walking surface can be used for purposes other than anticipatory stepping control, bearing important motor-control and clinical implications.

Testing of path-based visual cues on patterned carpet to assist older adults' gait in a continuing care retirement community

Fall accidents lead to hospitalization and medical costs among all age groups, especially severe for older adults. Both intrinsic (e.g., visual impairment, fear of falling) and extrinsic (e.g., inappropriate carpet design, poor lighting) factors contribute to fall accidents. Older adults increasingly rely on visual perception to maintain balance as their health conditions decline. Patterned carpet is common in the built environment, which is one of the factors contributing to fall accidents among older adults. This study examined the role of path-based visual cues (provide visual guidance while walking along the patterned carpet) in helping older adults maintain safe movement and overcome the fear of falling. The experimental field study was conducted at a Continuing Care Retirement Community. Thirty-two residents were recruited. Within-subjects design was employed to examine the effects of path-based visual cues (light color and brightness) on the gait characteristics of older adults with and without visual impairment while walking on patterned carpet. Wearable sensors collected older adults' gait characteristics and questionnaires were used to evaluate their perceptions of confidence and safety with different visual cues provided. Individual repeated measures analysis results indicated that older adults significantly decreased stride length and stride velocity under 8.3 fc white and 7.3 fc blue lighting conditions compared to the baseline condition. In addition, the principal component analysis also indicated significant differences in gait performance among lighting colors and lighting brightness. The subjective responses indicated that the path-based visual cues were helpful in improving walking confidence, particularly for older adults with visual impairment.

Performance of ground-level signal detection when using a phone while walking

Ground-level traffic lights or safety signs have been introduced recently as a prevention measure for smartphone-related pedestrian accidents. However, quantitative evaluation of smartphone users' detection performance during distracted walking has been scarce. A laboratory experiment was conducted to evaluate the performance of detecting ground-level visual cues during the concurrent use of a smartphone while walking. Thirty-eight young smartphone users performed ground-level visual cue detection trials, 1) while walking upright on a treadmill without using a smartphone; 2) when conducting one-handed browsing while walking; and, 3) when conducting two-handed texting while walking. Visual cues were presented on the ground at 24 locations by a ceiling-mounted projector, and participants were asked to respond verbally when they perceived the appearance of each cue. Study results show that the concurrent use of a smartphone decreased the detection rate significantly (p < 0.05) from 93.5 % to 76.3∼74.1 %, and increased the reaction time from 0.90 s to 1.04∼1.15 s. Among the 24 cue locations, cues that were presented closer to participants were detected significantly (p < 0.05) more often and faster than cues that were shown at further locations. The results of this laboratory-based study imply that the ground-level signals might not be detected well by smartphone users, specifically when they were conducting more demanding tasks such as texting while walking. However, the laboratory conditions were confined to a specific usage environment; therefore, future research should be focused on the situation awareness of smartphone users under various usage scenarios and more realistic environments.

Attentional prioritization in dual-task walking: Effects of stroke, environment, and instructed focus

BACKGROUND

The impact of high distraction, real-world environments on dual-task interference and flexibility of attentional prioritization during dual-task walking in people with stroke is unknown.

RESEARCH QUESTION

How does a real-world environment affect dual-task performance and flexible task prioritization during dual-task walking in adults with and without stroke?

METHODS

Adults with stroke (n = 29) as well as age-, gender-, and education-matched adults without stroke (n = 23) participated. Single and dual-task walking were examined in two different environments (lab hallway, hospital lobby). Two different dual-task combinations were assessed (Stroop-gait, speech-gait). Each dual-task was performed first without explicit instruction about task prioritization (no-priority) and then with gait-priority instruction and Stroop/speech-priority instruction in randomized order.

RESULTS

People with stroke had significantly slower dual-task gait speed (Stroop only) in the lobby than the lab, but the effect was not clinically meaningful. Stroop reaction time for all participants was also slower in the lobby than the lab. All participants slowed their walking speed while generating spontaneous speech, but this effect was not influenced by environment. The dual-task attention allocation strategy was generally inflexible to instructed prioritization in adults with and without stroke in both environments, however, the volitional attention allocation strategy differed for the two dual-task conditions such that speech was prioritized in the speech-gait dual-task and gait appeared to be prioritized in the Stroop-gait dual-task.

SIGNIFICANCE

Although dual-tasking slows walking speed and verbal responses to auditory stimuli in people with stroke, the effects are not considerably impacted by a more complex, distracting environment. Adults with and without stroke may have difficulty overriding the preferred attention allocation strategy during dual-task walking, especially for habitual dual-tasks such as walking while speaking. It may also be that the cognitive control strategy governing task prioritization is influenced by degree of cognitive engagement.

The Effect Of Visual Dual-Tasking Interference On Walking In Healthy Young Adults

BACKGROUND

Visual dual-task skills are essential for stable ambulation in everyday life such as walking while reading text. Gait analysis in a virtual environment can provide insight into altered walking performance while visual dual-tasking.

RESEARCH QUESTION

How visual dual-tasking including cognitive load of reading text and altered optical flow influences walking speed and stability in healthy adults? Also, is there a relationship between the mediolateral centre of mass(CoM) displacement and mediolateral trunk movement?

METHODS

Nineteen able-bodied young adults performed self-selected walking on a treadmill in a virtual environment under the following three conditions; single-task walking, walking while viewing scrolling lines, and walking while reading text scrolling on the screen. Three-dimensional motion analysis was used to measure the effect of dual-tasking on gait velocity, step length, mediolateral CoM displacement, and mediolateral thorax inclination.

RESULTS

The effect of visual dual-tasking showed significantly increased walking speed and longer step length compared to single-tasking. The cognitive load of reading text while walking had a significant impact on reduced step length variability and greater mediolateral CoM displacement. This was related to the mediolateral thorax inclination.

SIGNIFICANCE

A visual dual-task influences gait through altered optical flow and a cognitive load effect. Altered optical flow increased walking speed whilst the visual attention to read text affected foot placement and upright trunk posture, together with greater mediolateral CoM displacement. Thus, dual-tasking of reading text in a virtual environment substantially affected walking stability in healthy young people. This paradigm is therefore useful for assessment of walking stability in daily life and in the clinical setting.

Training or Battling a Monster of a Location-Based Augmented-Reality Game While Descending Stairs: An Observational Study of Inattentional Blindness and Deafness and Risk-Taking Inclinations

Several emerging smartphone location-based augmented-reality (AR) games require three primary tasks: training or battling a monster, capturing a monster, and searching for a monster, which involve different levels of perceptual load. Using the AR game originated from Japan as a single case study, this study examined inattentional blindness and deafness and risk-taking inclinations among participants concurrently descending stairs and engaging in these three tasks. Participants descending stairs in Taipei Medical University were observed through recordings obtained from Wi-Fi cameras to determine whether they engaged in risk-taking behaviors such as hopping, not using the handrail, and stopping suddenly. After the participants descended the stairs, they were interviewed to obtain additional information regarding demographics, game tasks (training or battling a monster, capturing a monster, or searching for a monster), data plan, and screen size. Inattentional blindness and deafness were investigated by determining whether participants saw something unusual, a police ascending the stairs, and heard the national anthem played by the police, respectively. In total, 1036 participants descended the stairs and underwent the interview between August 2016 and July 2018. Logistic regression models revealed that training or battling a monster was most associated with inattentional blindness, deafness, not using the handrail, and stopping suddenly, whereas hopping behavior was the commonest among those capturing a monster. Other contributory factors include a large smartphone screen (≥5 in), unlimited mobile data, being an undergraduate student, and an increase in the daily gaming hours. Development of smartphone apps toward detection of stair locomotion may be beneficial for curbing phone use in general and AR game playing in particular.