A novel experimental setup combining EEG and robotics to investigate brain activity driving controlled reaching movements in chronic stroke survivors

When chronic, hemiparetic stroke survivors make reaching movements while lifting the paretic arm against gravity, their ability to generate the necessary independent joint movements for reaching degrades dramatically due to abnormal muscle coactivation patterns that couple shoulder abduction with elbow flexion. The neural mechanisms behind the appearance of abnormal coordination patterns during post-stroke recovery are largely unknown, but they are possibly related to a loss in cortical resolution and an increased usage of undamaged, indirect descending motor pathways via the brainstem. In order to investigate the underlying mechanisms for this behavior in chronic stroke survivors, we have developed a novel experimental setup that simultaneously records electroencephalographic (EEG) signals while the test subject makes different reaching movements with an ACT^3D robot. This method allows us to map brain activity during controlled reaching movements with different levels of robot-mediated limb support for the first time. Our results provide evidence for changes in cortical activity driving realistic upper-extremity reaching movements as independent joint control becomes compromised in stroke survivors.