Our research has several main thrusts. These focus on the use of devices that interface between computers and muscles or directly between computers and the brain. We use these powerful interfaces as paradigms to try to improve our understanding of brain function. In addition, our ultimate goal is to use them to improve our treatment of neurologic disorders.
Myoelectric interfaces for neurorehabilitation (MINT)
Stroke is one of the leading causes of chronic disability worldwide. One of the main contributors to impaired arm or leg function after stroke is abnormal coordination between limb muscles. For example, abnormal co-activation between biceps and anterior deltoid muscles prevents the ability to reach out and straighten the arm. We are developing a new therapy for stroke using a wearable device (a myoelectric interface for neurorehabilitation, or MINT) to improve motor function by decoupling abnormally co-activating muscles. MINT conditioning allows participants to control customized video games using the electrical activity produced by their co-activating muscles. The games are designed to train the participants to reduce abnormal co-activation in an entertaining and motivating fashion. The goal is to produce an affordable, wearable version that can be used in the home with portable devices to enable high-intensity, highly customizable treatment. Our initial studies suggest that MINT can reduce co-activation and improve arm movement. Our randomized, controlled clinical trials are testing this with home-based training in chronic and acute stages after stroke. We are also investigating some mechanisms behind improvement.
Enhancing MINT with sleep-based training
Learning a new memory or a new skill involves more than just practice; learning continues to occur “offline,” and in particular during sleep. This process is called consolidation. This process can be enhanced by pairing a given memory with a sound and then playing back the sounds during sleep – this is called targeted memory reactivation (TMR). We recently partnered with the Paller lab at Northwestern, where TMR was pioneered, to show that TMR can also enhance training with a myoelectric interface motor learning in healthy participants. We are now testing the ability of TMR to improve MINT conditioning in stroke survivors. MINT conditioning and TMR are both done at home with wearable devices, with the goal of reactivating memories of the training while participants sleep. We are testing its effects on co-activation and arm function. We are also investigating the mechanisms behind MINT and TMR enhancement using MRI, transcranial magnetic stimulation, and startle responses.
Brain machine interfaces to restore communication
Many neurological disorders, such as stroke, ALS, and cerebral palsy, can severely impair people’s ability to speak or communicate in any manner. For these individuals, the ability to restore communication is paramount. Brain machine interfaces (BMIs; also called brain computer interfaces), which decode electrical signals recorded from the brain, offer one way to restore communication to these individuals. One way to do this in an efficient, high-throughput manner would be to decode the patient’s intended speech from the speech and language network of the brain. That is, the patient would attempt to speak and the BMI would directly decode entire words and sentences, with minimal delays. This is essential to restoring autonomy to patients with these impairments. We have been working toward this goal of decoding speech with BMIs, primarily using brain signals recorded intracranially from people with intact speech who require brain surgery for treatment of epilepsy or brain tumors. 
Words in a language are composed of groups of sounds, or phonemes. Signals recorded from the surface of the cortex contain information about phonemes based on the location of phoneme production by articulators (e.g., tongue vs. lips).We have shown that different areas of the brain may be optimal for decoding phonemes vs. the movements of articulator muscles (Mugler et al, J Neuroscience, 2018). In addition, we have shown the ability to decode directly the participants produced audio signals as well (Angrick et al, J Neural Engineering 2019). We are continuing to investigate how the brain controls speech and language production. We anticipate that this will ultimately enable us to restore intuitive communication to patients with severe communication impairment.
Understanding electrocortical stimulation used in functional brain mapping
Current treatment of neurological disorders like epilepsy, brain tumors, and chronic pain (among others) often involves “mapping” brain function using electrocortical stimulation (ECS). This method of exploring brain function dates back well over 100 years and has been accepted clinical practice for many decades. Surprisingly, and in spite of this long history, the precise mechanisms of ECS are not well understood. How exactly does ECS impact individual neurons in the cerebral cortex? Is it having purely local effects, or do its effects at a given location depend upon the connectivity between that location and other brain areas? We are currently undertaking a project to examine these questions using graph theory, cortical cooling, and calcium imaging. A better understanding of the impact of ECS could enable doctors and hospitals to refine their use of this common tool, potentially improving diagnosis and treatment of highly debilitating neurological disorders.
