Modeling the cortical response elicited by wrist manipulation via a nonlinear delay differential embedding

Abstract

Regarding motor processes, modeling healthy people's brains is essential to understand people with motor impairments' brain activity. However, little research has been undertaken when external forces disturb limbs, having limited information on physiological pathways. Therefore, in this paper, a nonlinear delay differential embedding model is used to estimate the brain response elicited by externally controlled wrist movement in healthy individuals. The aim is to improve the understanding of the relationship between a controlled wrist movement and the generated cortical activity of healthy people, helping to disclose the underlying mechanisms and physiological relationships involved in the motor event. To evaluate the model, a public database from the Delft University of Technology is used, which contains electroencephalographic recordings of ten healthy subjects while wrist movement was externally provoked by a robotic system. In this work, the cortical response related to movement is identified via Independent Component Analysis and estimated based on a nonlinear delay differential embedding model. To validate the model, a cross-validation analysis is performed, achieving 90.21% ➧ 4.46% Variance Accounted For, and Correlation 95.14% ➧ 2.31%. The proposed methodology allows to select the model degree, to estimate a general predominant operation mode of the cortical response elicited by wrist movement. The obtained results revealed two facts that had not previously been reported: the movement's acceleration affects the cortical response, and a common delayed activity is shared among subjects. Going forward, this approach may pave the way for further analysis of various treatments effectiveness for people with upper limbs motor impairments.