Elsevier

Gait & Posture

Volume 40, Issue 1, May 2014, Pages 182-186
Gait & Posture

Attentional costs of visually guided walking: Effects of age, executive function and stepping-task demands

https://doi.org/10.1016/j.gaitpost.2014.03.183Get rights and content

Highlights

  • Attentional costs of walking were assessed as a function of age and executive function.

  • Task demands were manipulated using visual stepping targets.

  • Increased task demands induced increased attentional costs in young adults.

  • Increased task demands had less effect on attention allocation in elderly adults.

  • This finding was more prominent for elderly with lower executive function.

Abstract

During walking, attention needs to be flexibly allocated to deal with varying environmental constraints. This ability may be affected by aging and lower overall executive function. The present study examined the influence of aging and executive function on the attentional costs of visually guided walking under different task demands. Three groups, young adults (n = 15) and elderly adults with higher (n = 16) and lower (n = 10) executive function, walked on a treadmill in three conditions: uncued walking and walking with regular and irregular patterns of visual stepping targets projected onto the belt. Attentional costs were assessed using a secondary probe reaction time task and corrected by subtracting baseline single-task reaction time, yielding an estimate of the additional attentional costs of each walking condition. We found that uncued walking was more attentionally demanding for elderly than for young participants. In young participants, the attentional costs increased significantly from uncued to regularly cued to irregularly cued walking, whereas for the higher executive function group, attentional costs only increased significantly from regularly cued to irregularly cued walking. For the group with lower executive function, no significant differences were observed. The observed decreased flexibility of elderly, especially those with lower executive function, to allocate additional attentional resources to more challenging walking conditions may be attributed to the already increased attentional costs of uncued walking, presumably required for visuomotor and/or balance control of walking.

Introduction

Accurate foot placement, especially under challenging environmental conditions, is essential to prevent slips, trips or misplaced steps that are common causes of falls in elderly individuals [1]. Various intrinsic factors contribute to successful stepping performance, including higher-level cognitive functions, such as attention [2]. Assessing residual processing capacity during visually guided walking helps to reveal the amount of attention required for accurate stepping. Excessive cognitive effort invested in foot placement can limit an individual's ability to attend to environmental hazards leading to increased fall risk. Dual-task paradigms have demonstrated that increased age is associated with greater attention allocation to foot placement during walking [3], particularly in elderly individuals with a higher risk of falling [4].

While the ability to adapt stepping behavior has been assessed in relation to various environmental constraints such as an obstacle [5] or a curb [6], other studies have exploited visual or auditory cues to assess gait adaptability, especially in neurological [7], orthopedic [8] and geriatric [9], [10] populations. Compared to uncued walking, attentional costs increased when steps were adjusted to external cues, with visual cues (projected stepping stones) demanding more attention than auditory cues (metronome beeps) [10]. This result highlights the predominant role of visual information in gait control, particularly in environments that demand visually guided step adjustments [11].

Several factors may influence the relationship between visually guided step adjustments and associated attentional demands. To unravel the effect of age on this relationship, Peper et al. [10] examined the attentional demands of visually cued walking in young and elderly adults. The attentional demands were higher for elderly participants for all cued and uncued conditions, but the increase in attentional demands over the conditions was comparable for both age groups. In addition, decreased functioning of specific cognitive domains, such as executive function (EF) [12] may affect age-related deficits in attentional demands of walking. EF represents coordinated action of cognitive processes such as attention, planning, response monitoring and response inhibition, and is essential for successful performance of goal-directed activities in a flexible manner [13]. Impairment of one or more of these processes may decrease the ability to efficiently deal with changes in walking task demands [13]. Indeed, EF is a predictive factor for fall risk among older adults [14] and is associated with stepping performance, particularly under increased environmental complexity [15]. A third important factor in visually guided stepping is terrain complexity [11]. Visually guided stepping becomes less accurate with increased environmental complexity [8] and this effect is more prominent in elderly individuals [16].

To date, the roles of age, EF, and terrain complexity in visually guided walking have mostly been studied in relation to stepping performance [8], [15], [16]. In the current study we focused on how these factors influence the attentional demands of visually guided walking. To this end, we recruited elderly participants (considerably older than those in [10]) with lower EF (LEF) or higher EF (HEF) and a group of young adults. Because attentional demands of walking appear to be minimal at one's preferred speed and gait pattern [17], [18], all participants walked at their self-selected comfortable walking speed under three conditions: uncued walking and walking onto regular and irregular patterns of stepping targets, with the patterns of stepping targets being based on each individual's preferred gait pattern. In this way we created comparable conditions for all participants. We used a probe reaction time (RT) task to assess the associated attentional demands and hypothesized that RT would be higher for cued than uncued walking, in particular when the stepping stones were irregularly spaced. These differences were expected to be larger for elderly participants, especially for those with LEF, compared with young participants. In line with previous findings [3], we also expected higher attentional costs for the elderly groups compared to young participants for uncued walking. Furthermore, visually guided stepping was hypothesized to be less accurate for walking onto an irregular than a regular sequence of stepping targets, again most markedly so for older adults and particularly those with LEF.

Section snippets

Participants

Fifteen young adults and two groups of elderly adults with either HEF (n = 16) or LEF (n = 10) participated (see Table 1). Exclusion criteria were self-reported cardiovascular or cardiopulmonary problems, orthopedic conditions, uncorrected visual or auditory impairments, neurological diseases, other conditions limiting mobility, use of walking aids and Mini Mental State Exam (MMSE) score below 19 (actual scores all ≥26; Table 1). The older adults were selected from a cohort of 148 elderly who had

Group characteristics

Table 1 presents the participants’ characteristics for the three groups. Age, height, weight, TUG, and MMSE were similar for the HEF and LEF groups, but compared to young participants age was higher in both elderly groups and height was lower in the HEF group. Regarding EF, the HEF group scored better than the LEF group on both the TMT (B/A ratio) and SCWT, while the young participants outperformed both elderly groups on the SCWT. Young participants walked faster than both elderly groups,

Discussion

As expected, the attentional costs of uncued walking were significantly lower for young participants compared to both elderly groups. Moreover, cued walking, in particular stepping onto irregularly spaced stepping targets, required more attention than uncued walking. However, the effect of increased stepping-task demands on attentional costs differed between the three groups in a way that deviated from our hypothesis. Whereas in the young group, ΔRT indeed increased from uncued to regularly

Acknowledgments

The authors thank Niels Waterval and Femke Bijen for their generous assistance in the data collection and Mirjam Pijnappels, Kim van Schooten, and Miek de Dreu for their invaluable contribution to the recruitment of elderly participants. This research was conducted as part of MOVE-AGE, an Erasmus Mundus Joint Doctorate programme (2011–2015) funded by the European Commission.
Conflict of interest

We are not aware of any conflicts of interest that may have affected the outcomes of our study.

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