Examination of visual reliance and the exploitation of visual information in old adults’ postural control and navigation abilities

Absctract: Healthy aging is characterized by a decline in many perceptual, cognitive and motor abilities. Although not exacerbated to the point of pathology, such age-related deficits are considered to affect daily living tasks in old adults, ultimately leading to loss of autonomy and health risks, most notably falls. Postural control and safe/successful navigation require the integration of sensory information (visual, vestibular and kinesthetic) that are associated with multiple executive functions (e.g. attention, planning, memory). Sensory signals must be appropriately weighed depending on the environment and motor task difficulty (for example when walking in a crowded setting or on hazardous ground surfaces), in order to maximise their reliability and, consequently, modulate their contribution to postural control for stance and locomotion. Among the factors contributing to daily living risks in old age, some may be associated with a degradation in sensory (re)weighting, leading to a greater reliance on visual cues. Indeed, with old age, there is a greater reliance on visual feedback for postural control, especially with regards to the ground surface (Agathos et al., 2017a). Visual reliance however implies a lack of adaptability (Isableu et al., 2010) and an exploitation of visual cues that may not always be optimal given that old adults are less able to ignore disorienting visual contextual information and to allocate and share visual attention resources (Agathos et al., 2015). Postural control is therefore a greater challenge for old adults whilst in unfamiliar, complex or dynamically changing environments. Faced with such challenges, old adults’ visual reliance leads to postural alterations by adopting more rigid strategies (Agathos et al., 2017b) which can increase fall risk (Barr et al., 2016). In a counter-intuitive fashion, however, old adults are less able to use visual landmarks for reorientation in spatial navigation. Indeed, work in our laboratory has demonstrated that old adults preferentially use geometry to reorient themselves and tend to direct their gaze toward the ground (Bécu et al., 2017). This may be a strategy to minimize the attentional resources required to both explore a visual environment and guide action. Such a strategy can be characterized by old adults’ gaze-postural dynamics during learning and reorienting in a novel ecological environment.