Exploring the Effects of Cognitive Load on Muscle Activation during Functional Upper Extremity Tasks

Abstract

Voluntary movements of reach and grasp are essential in our daily activities. Pathologies such as stroke, spinal cord injury, cerebral palsy, etc. hinder the ability to perform meaningful upper extremity movements, leading to severe reduction of independence and quality of life. Electromyography (EMG) controlled devices are gaining prevalence as clinical rehabilitation and assistive tools. A common controller design used is the threshold crossing method of detecting ‘rest’ and ‘active’ states. Such an overtly simple control scheme is not robust and lacks the ability to account for task specific information in addition to not providing information regarding strategies used by the central nervous system in realizing the desired movements. This causes an increased risk of inducing compensatory behaviors that lead to reduced functional recovery and other health complications. In this study, we explore the influence of task cognitive loads as manifested through the geometric properties of a set of objects on the response features of the EMG signals collected from the biceps and triceps muscles during the reaching phase of a series of tasks performed during a motion analysis study using healthy subjects (N=5). Our preliminary results show the presence of differences that are particular to the geometric properties of each object, suggesting the existence of task specific neural encoding and schemata used by the central nervous system for the control of object manipulation and reach. This study is important as it will help provide some insight with regards to factors that need to be considered during the development of future robust controllers for EMG triggered upper extremity functional rehabilitation tools.