The ability to learn and produce skilled movements is required for humans to successfully engage with each other and their environment. A principal role of the brain is to guide current, and plan future, movements based on past actions and potential rewards. In this talk, I will describe ongoing work in our lab employing multiple approaches to investigate the functional contributions of brain activity to normal and abnormal human movement. I will discuss how transcranial magnetic stimulation (TMS), a form of non-invasive brain stimulation, can be used both characterize and modulate cortical activity and connectivity during movement. I will also describe our recent findings showing abnormal TMS-evoked cortical reactivity post-stroke that is related to persistent paretic arm impairment. Lastly, I will discuss preliminary work applying alternative perturbation paradigms to study brain-behavior relationships in health and disease.
Up to 80% of stroke survivors have persistent motor impairment of the paretic arm that interferes with performing functional activities and limits activity participation. Stroke can trigger maladaptive changes in the strength and organization of structural and functional connections between brain regions. During paretic arm movement, there is exaggerated interhemispheric inhibition (IHI) from the contralesional hemisphere to the ipsilesional hemisphere. Exaggerated IHI creates an abnormal activity imbalance between brain hemispheres and this imbalance seems to be a primary contributor to motor impairment of the paretic arm after stroke. Although restoring the balance of activity between brain hemispheres has been a primary target of many novel rehabilitation strategies, limited progress has been made to improve arm motor function and reduce persistent disability for stroke survivors.
In this talk, I will describe work in our lab using transcranial magnetic stimulation (TMS), a form of non-invasive brain stimulation, to both characterize and modulate cortical activity and connectivity in the brain after stroke. In the first part of my talk, I will describe how abnormal cortical excitability after stroke has been traditionally characterized using standalone TMS techniques. In the second part of my talk, I will discuss current findings from our lab using concurrent EEG recordings of TMS-evoked cortical activity that demonstrate abnormal interhemispheric interactions are present in the human brain after stroke and these abnormal interactions are related to arm motor impairment. Finally, I will introduce an upcoming project in our lab investigating the use of bifocal TMS to transiently modulate local cortical excitability and IHI in the human brain in an effort to restore the balance of activity between the hemispheres and improve arm motor function after stroke.