Visuomotor Prosthetic for Paralysis

The investigators objective is to run human clinical trials in which brain activity recorded through a "brain-chip" implanted in the human brain can be used to provide novel communication capabilities to severely paralyzed individuals by allowing direct brain-control of a computer interface. A prospective, longitudinal, single-arm early feasibility study will be used to examine the safety and effectiveness of using a neural communication system to control a simple computer interface and a tablet computer. Initial brain control training will occur in simplified computer environments, however, the ultimate objective of the clinical trial is to allow the human patient autonomous control over the Google Android tablet operating system. Tablet computers offer a balance of ease of use and functionality that should facilitate fusion with the BMI. The tablet interface could potentially allow the patient population to make a phone call, manage personal finances, watch movies, paint pictures, play videogames, program applications, and interact with a variety of "smart" devices such as televisions, kitchen appliances, and perhaps in time, devices such as robotic limbs and smart cars. Brain control of tablet computers has the potential to greatly improve the quality of life of severely paralyzed individuals. Five subjects will be enrolled, each implanted with the NCS for a period of at least 53 weeks and up to 313 weeks. The study is expected to take at least one year and up to six years in total.

The objective of the proposed research is to obtain scientific knowledge of visuomotor transformations in posterior parietal cortex (PPC) and primary motor cortex (M1) from tetraplegic subjects in a clinical trial to advance the development of neural prosthetics. We have shown in clinical trials conducted over the past 6 years that PPC can control neural prosthetics for assisting tetraplegic subjects. Other groups have concentrated on M1 and likewise find control for neural prosthetics. In our studies of PPC we have found that besides trajectory signals to move robotic limbs or control computer cursors, there are a plethora of visuomotor signals that represent intended movements of most of the body, movement goals, cognitive strategies, and even memory signals. Our central hypothesis is that PPC and M1 will encode visuomotor parameters in both similar and different ways, and that algorithms can be developed to leverage those signals from the two areas that are complimentary to improve prosthetic range and performance. Implants will be made in both M1 and PPC, enabling simultaneous recording in the same subjects, elevating concerns of comparing data from different labs collected in different individuals with different implants and different tasks.

This central hypothesis will be tested in two broad aims, for which we have substantial preliminary data. Aim 1 will examine the control of the body by the two areas. It is hypothesized that M1 will demonstrate strong specificity for the contralateral limb (implants will be made in the hand knob) whereas PPC will code movements for most of the body and on both contra and ipsilateral sides by leveraging its partially mixed encoding of parameters (subaim 1a). Whereas M1 is hypothesized to code spatial variables exclusively during attempted or imagined actions, it is hypothesized that PPC also encodes cognitive spatial variables in task appropriate reference frames (subaim 1b). In subaim 1c we will examine how multiple body parts are combined in movement representations, hypothesizing that M1 and PPC will employ a diverse set of mechanisms including linear summation, non-linear combinations, and movement suppression expressed in different ways as a function of brain area and the specific movement set.

Aim 2 will examine the temporal aspects of encoding in the two areas. In subaim 2a we will test the hypothesis that the neural dynamics during sustained periods of movement are largely unchanging in both areas. In subaim 2b we hypothesize that, during sequential movements, M1 codes only the ongoing movement whereas PPC codes both the current and subsequent movements. Finally, in subaim 2c we will examine the coding of movement speed, with the hypothesis that there are separate subspaces in both M1 and PPC for direction and speed of movement.