Mobile electroencephalography captures differences of walking over even and uneven terrain but not of single and dual-task gait

Abstract

Walking on natural terrain while performing a dual-task, such as typing on a smartphone is a common behavior. Since dual-tasking and terrain change gait characteristics, it is of interest to understand how altered gait is reflected by changes in gait-associated neural signatures. A study was performed with 64-channel electroencephalography (EEG) of healthy volunteers, which was recorded while they walked over uneven and even terrain outdoors with and without performing a concurrent task (self-paced button pressing with both thumbs). Data from n = 19 participants (M = 24 years, 13 females) were analyzed regarding gait-phase related power modulations (GPM) and gait performance (stride time and stride time-variability). GPMs changed significantly with terrain, but not with the task. Descriptively, a greater beta power decrease following right-heel strikes was observed on uneven compared to even terrain. No evidence of an interaction was observed. Beta band power reduction following the initial contact of the right foot was more pronounced on uneven than on even terrain. Stride times were longer on uneven compared to even terrain and during dual- compared to single-task gait, but no significant interaction was observed. Stride time variability increased on uneven terrain compared to even terrain but not during single- compared to dual-tasking. The results reflect that as the terrain difficulty increases, the strides become slower and more irregular, whereas a secondary task slows stride duration only. Mobile EEG captures GPM differences linked to terrain changes, suggesting that the altered gait control demands and associated cortical processes can be identified. This and further studies may help to lay the foundation for protocols assessing the cognitive demand of natural gait on the motor system.

Keywords: ERSP; dual-task; gait; mobile EEG; terrain.

Figure 1

(A) Map of the two routes with different terrain (B) picture of the even terrain (C) experimental structure outdoors (D) picture of the uneven terrain.

Figure 2

EEG preprocessing and artifact attenuation pipeline.

Figure 3

Mean stride time (A) and stride time variability (B) across subjects. Error bars indicate the standard error of the mean.

Figure 4

(A) Gait artifact-related footprint without (dashed) and with (solid) artifact attenuation with the following features: (feature B) explained variance across frequencies, (feature C) lateral to medial channel power ratio, (feature D) neck channel power ratio, (feature E) double support power ratio, (feature F) standing/walking power ratio. (B) Raincloud plots (80) of euclidean distances of footprint feature vectors with and without artifact attenuation. Single subjects represented by dots.

Figure 5

ERSPs at Cz without (A) and with (B) artifact attenuation. (C) Comparison of ERSP spectral power at Cz without (orange) and with (blue) artifact attenuation. Mean beta power (20 to 30 Hz, across the gait cycle) topographies and source activity without (D) and with (E) artifact attenuation. GPMs at Cz without (F) and with (G) artifact attenuation. (H) Comparison of GPM absolute spectral power at Cz without (orange) and with (blue) artifact attenuation. Mean absolute beta power (20 to 30 Hz, across the gait cycle) topographies and source activity without (I) and with (J) artifact attenuation.

Figure 6

Grand average GPM at Cz of all conditions from 6 to 40 Hz across the whole gait cycle (0% initial contact right to 100% next initial contact right). Cluster uncovered with nonparametric permutation tests marked with a solid outline. Topography and projected sources of the cluster mean on the right side.