Natural Translating Locomotion Modulates Cortical Activity at Action Observation.

Thierry Pozzo,Claudio Campus,Ghislain Saunier,Stefano Panzeri,Alejo Keuroghlanian,Alberto Inuggi

doi:10.3389/fnsys.2017.00083

Abstract

The present study verified if the translational component of locomotion modulated cortical activity recorded at action observation. Previous studies focusing on visual processing of biological motion mainly presented point light walker that were fixed on a spot, thus removing the net translation toward a goal that yet remains a critical feature of locomotor behavior. We hypothesized that if biological motion recognition relies on the transformation of seeing in doing and its expected sensory consequences, a significant effect of translation compared to centered displays on sensorimotor cortical activity is expected. To this aim, we explored whether EEG activity in the theta (4–8 Hz), alpha (8–12 Hz), beta 1 (14–20 Hz) and beta 2 (20–32 Hz) frequency bands exhibited selectivity as participants viewed four types of stimuli: a centered walker, a centered scrambled, a translating walker and a translating scrambled. We found higher theta synchronizations for observed stimulus with familiar shape. Higher power decreases in the beta 1 and beta 2 bands, indicating a stronger motor resonance was elicited by translating compared to centered stimuli. Finally, beta bands modulation in Superior Parietal areas showed that the translational component of locomotion induced greater motor resonance than human shape. Using a Multinomial Logistic Regression classifier we found that Dorsal-Parietal and Inferior-Frontal regions of interest (ROIs), constituting the core of action-observation system, were the only areas capable to discriminate all the four conditions, as reflected by beta activities. Our findings suggest that the embodiment elicited by an observed scenario is strongly mediated by horizontal body displacement.

Highlights

Human locomotion is possible thanks to central pattern generators allowing a reciprocal activation of flexors and extensors muscle (Grillner and Wallen, 1985)
Cyclical locomotor skill became a decisive step in species evolution when displacement started to be oriented and goal directed
If motion recognition relies on the transformation of seeing in doing and its expected sensory consequences, a significant effect of translation compared to centered displays on sensorimotor cortical activity is expected

Summary

Introduction

Human locomotion is possible thanks to central pattern generators allowing a reciprocal activation of flexors and extensors muscle (Grillner and Wallen, 1985). Backward or forward displacements to avoid a predator or Cortical Correlates of a Translating Point-Light Walker to reach a prey include a variety of related cognitive processes. Instance of this is spatial navigation toward a goal and the ability to integrate body translation over time that originates from visual flow and vestibular input. As a teleokinetic behavior (Hess, 1943) is much more than central pattern generator activation producing limb oscillation as when walking on the spot. At the perceptual level, a walker on the spot corresponds to an erratic walker without goal, as someone can do for fun in the reverse direction of an airport treadmill, that is a rather atypical visual stimulus

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