Restoring function after neuromuscular trauma: novel paradigms for enhancing volitional control of neural activity in untethered environments and vHAB, a gamified therapy platform

Thesis (Ph.D.)--University of Washington, 2016-08

Individuals suffering from neuromuscular traumas, such as stroke and spinal cord injury, face limited options in regaining motor function after injury. Emerging methods in brain-machine interfaces aim to assist individuals by directly connecting brain signals with assistive technologies. Human BMI studies are limited, leaving most studies to rely on models. Monkey studies are typically conducted in constrained booths under controlled conditions using brain areas that modulate with motor behavior. These approaches present challenges in translating to human populations with varying motor mappings, residual movement abilities, and cortical damage. These methods require years of work before seeing widespread adoption, leaving traditional methods as the leading treatment for most patients. Here, we present four novel approaches to these problems. First, we present a rewarding brain-stimulation paradigm in unconstrained primates. To reward increases in cell activity, we sought sites in nucleus accumbens (NAc) whose stimulation reinforced operant responding. Spikes occurring above baseline rates triggered electrical pulses to the reinforcement site. In-booth conditioning produced increases in neuron firing in 48 of 58 cells. In-cage conditioning produced significant increases in 21 of 33 sessions. Second we developed a feeder and behavior monitoring system specifically designed for BMI applications. This system interfaces existing untethered recording equipment with a hub that controls a cage-mounted feeder. The behavior monitoring system uses a depth camera to provide real-time, easy to analyze, gross movement data streams. In a proof-of-concept experiment we demonstrated robust control and learning of the system over 14 sessions. Next we describe the development of a gamified therapy system, vHAB, designed to enhance traditional recovery methods. vHAB consists of engaging games based on therapy tasks, automated analytics that describe patient progress, and carefully selected commodity hardware. Developing versions of the vHAB system were used at multiple pilot sites and two studies. Finally, we relate initial promising results of the use of the prefrontal cortex as a non-motor area for BMI applications. Single neurons and local field potentials of the prefrontal cortex were conditioned in a constrained environment with three monkeys. Initial results were limited due to hardware complications, but monkeys showed signs of learning the task.