The overall goal of this project is to advance the understanding of how cortical microstimulation information can be interpreted and used by primates. The project will test the hypothesis that cortical microstimulation cues can be properly discriminated and utilized by primates, and that discriminations can be made according to such microstimulation parameters as amplitude, temporal frequency/pattern, and spatial frequency/pattern. This hypothesis will be tested by monitoring learning and performance of a choice task, while the animal is delivered cortical microstimulation cues that differ along one, or several, of the aforementioned parameters. The animal will first be trained on the task using other sensory cues, vibration or visual information. The task will start out as a choice task in which stimulation waveforms differ along a single parameter space, but will be expanded to a task in which stimulation waveforms differ along several parameter spaces. In this expanded task, the primates will have a bank of stimuli that makes up their vocabulary, and discriminations will be performed along a single parameter space that changes between experimental sessions. Thus, the project will test higher information flow rates and probe the limits of microstimulation based information delivery. Then, chronic electrode array recording technology will be used in concurrence with our developed stimulation discrimination task to probe the nature of microstimulation's effects on the various cortical structures involved in interpreting the microstimulation cues. Specifically, the project will explore the synchronous activity incited by microstimulation as it spreads into the surrounding cortical areas, as well as the cortical activity underlying the subsequent decision making process. Finally, the findings of the microstimulation and recording based probing will be integrated to build a closed-loop brain machine interface (BMI) in which continuous microstimulation feedback will be delivered as the primates' mental exploration of a reward space is decoded from neural recordings. This project as a whole will provide valuable information about conscious interpretation of direct cortical microstimulation, which will expand the necessary knowledge base for building future neuroprosthetics. BMIs offer the possibility of a therapeutic treatment for paralysis, an impairment affecting millions throughout the world that while well understood, has limited options for alleviation. By decoding activity at the level of the cortex and feeding information directly back from a prosthetic, BMIs are able to bypass many of the underlying conditions that result in paralysis. It is the source of feedback that this research seeks to address, explore, and develop in the form of direct cortical microstimulation.
