Direct and indirect effects of attention and visual function on gait impairment in Parkinson's disease: influence of task and turning

Abstract

Gait impairment is a core feature of Parkinson's disease (PD) which has been linked to cognitive and visual deficits, but interactions between these features are poorly understood. Monitoring saccades allows investigation of real-time cognitive and visual processes and their impact on gait when walking. This study explored: (i) saccade frequency when walking under different attentional manipulations of turning and dual-task; and (ii) direct and indirect relationships between saccades, gait impairment, vision and attention. Saccade frequency (number of fast eye movements per-second) was measured during gait in 60 PD and 40 agematched control participants using a mobile eye-tracker. Saccade frequency was significantly reduced in PD compared to controls during all conditions. However, saccade frequency increased with a turn and decreased under dual-task for both groups. Poorer attention directly related to saccade frequency, visual function and gait impairment in PD, but not controls. Saccade frequency did not directly relate to gait in PD, but did in controls. Instead, saccade frequency and visual function deficit indirectly impacted gait impairment in PD, which was underpinned by their relationship with attention. In conclusion, our results suggest a vital role for attention with direct and indirect influences on gait impairment in PD. Attention directly impacted saccade frequency, visual function and gait impairment in PD, with connotations for falls. It also underpinned indirect impact of visual and saccadic impairment on gait. Attention therefore represents a key therapeutic target that should be considered in future research.

Peer Review #1 of "Eye movement control during visual pursuit in Parkinson’s disease (v0.1)"

“…The lack of correlation between UPDRS score with gaze position difference is comparable to what has been found in previous studies (MacAskill et al, 2012;Stuart, Galna, Delicato, Lord, & Rochester, 2017). In addition, no correlation was found between eye gaze position difference and saccade rates ( =0.07, p = 0.85) or between disease duration and saccade rate during pursuit ( =-ρ ρ 0.22, p = 0.54) or between disease duration and other eye movement characteristics ( =0.19 p = ρ 0.6 for pursuit gain; =-0.24, p = 0.51 for eye position difference).…”

Saccade frequency response to visual cues during gait in Parkinson's disease: the selective role of attention

“…The study involved a convenience sample of 55 people with PD and 32 age‐matched healthy older adult controls. Due to the exploratory nature of this study, there were no specific previous cueing examples available to guide sample‐size requirements; therefore, previous eye‐tracking during walking research was used to base our sample‐size on (Galna et al ., ; Stuart et al ., , ). The study adhered to the Declaration of Helsinki and was approved by the ‘ Newcastle and North Tyneside NHS Research Ethics Committee 1 ’ (Ref: 13/NE/0128).…”

“…Saccades, particularly saccade frequency, form the basis of visual exploration and are influenced by both visual and attentional neural processes (Kimmig et al ., ), which provides a means to examine the mechanisms underlying response to visual cues. Our recent work has shown that people with PD make significantly fewer saccades when walking than age‐matched older adults particularly under a dual‐task (Galna et al ., ), with attentional mechanisms underpinning saccadic and gait impairment in PD (Stuart et al ., ). A visual cue intervention may ameliorate deficits by prompting more frequent saccades, as recent studies have shown that cues increase visual exploration (fixation number) during gait in PD (Vitorio et al ., ; Beck et al ., ), but the underlying mechanisms remain unclear.…”

Visual Cues Promote Head First Strategies During Walking Turns in Individuals With Parkinson's Disease

“…Individuals with PD are known to fixate on objects while turning which impedes anticipatory eye movements ahead of the turn, resulting in altered segment coordination during turning (Ambati et al, 2016;Stuart et al, 2017). This was evident, in the pre-trials of our study where anticipatory eye movements were not observed (Figure 1), and the resulting sequence of body reorientation occurred from the pelvis up (Figure 4).…”