Unexpected Terrain Induced Changes in Cortical Activity in Bipedal-Walking Rats.

Honghao Liu,Jiping He,Qiang Huang,Chuankai Dai,Pengcheng Xi,Minjian Zhang,Yafei Liu,Bo Li,Yiran Lang,Rongyu Tang

doi:10.3390/biology11010036

Abstract

Simple SummaryMost studies on cortical dynamics during walking require subjects to walk stably on specific terrain. In fact, humans or other animals are often disturbed by an abrupt change in terrains during walking. To study the impact of unexpected terrain on cortical activity, we analyzed the kinematics and electroencephalography (EEG) dynamics of bipedal-walking rats after encountering unexpected terrain. We found that the gait of rats after encountering the unexpected terrain were significantly different from normal walking. Furthermore, the activities of the left and right primary motor areas (M1), the left and right primary somatosensory areas (S1), and the retrosplenial area (RSP) are coupled to gait cycle phase and varied with the terrain conditions. These findings suggest that unexpected terrains induced changes in gait and cortical activity, and provide novel insights into cortical dynamics during walking.Humans and other animals can quickly respond to unexpected terrains during walking, but little is known about the cortical dynamics in this process. To study the impact of unexpected terrains on brain activity, we allowed rats with blocked vision to walk on a treadmill in a bipedal posture and then walk on an uneven area at a random position on the treadmill belt. Whole brain EEG signals and hind limb kinematics of bipedal-walking rats were recorded. After encountering unexpected terrain, the θ band power of the bilateral M1, the γ band power of the left S1, and the θ to γ band power of the RSP significantly decreased compared with normal walking. Furthermore, when the rats left uneven terrain, the β band power of the bilateral M1 and the α band power of the right M1 decreased, while the γ band power of the left M1 significantly increased compared with normal walking. Compared with the flat terrain, the θ to low β (3–20 Hz) band power of the bilateral S1 increased after the rats contacted the uneven terrain and then decreased in the single- or double- support phase. These results support the hypothesis that unexpected terrains induced changes in cortical activity.

Highlights

When humans and other animals walk, they cannot detect terrain changes in time due to blocked vision such as in low-light environment
There was no significant difference in the kinematic metrics (Figure 3A,E,F) in the right swing phase
Our research investigated the limb kinematics and cortical dynamics of bipedalwalking rats after encountering an unexpected terrain

Summary

Introduction

When humans and other animals walk, they cannot detect terrain changes in time due to blocked vision such as in low-light environment. Humans will consciously maintain posture stability by increasing step time and step width when walking on uneven terrains, especially in low-light environments [2]. Walking is thought to be driven by the spinal cord and subcortical neural circuits, and rarely requires the involvement of the cortex [7,8,9]. As such, these studies show that the brain contributes little to responding to and overcoming unexpected terrains during walking

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