A central problem in planning and performing sensory-guided actions is the neural conduction delay in propagating a signal from the cortex to the muscles and the delay of sensory feedback indicating that the intended movement was achieved. A purely reactive system would not explain the timing precision achieved during movement because feedback arrives too late to effectively update an ongoing movement. This problem necessitates a learned mapping from an intended movement to a likely motor command that will achieve that intention in a given environment. Understanding how this is done in the cortex will elucidate general cortical computation mechanisms as well as provide a better understanding of how to build neural prosthetics as a therapeutic device for quadriplegia or other movement disorders. Lesion studies and previous electrophysiological studies provide some clue where these models reside in the brain and have suggested that cortico-cortical interactions between posterior parietal cortex (PPC) and motor cortex may compute these models. However, no study has directly linked interactions of cortical areas with these theoretical models. In this study the use of dual multi-electrode arrays will allow the observation of groups of neurons in each of two connected cortical areas simultaneously during pursuit-tracking with the arm. A transient perturbation to hand position will be applied to induce errors in a forward sensory model. We propose that parietal area PE (part of PPC), in concert with motor cortex (MI), calculates a forward sensory model based on motor command, and that error signals computed from this model cause MI to drive corrective movements on a perturbation.
The importance and health relevance of this project are in the direct knowledge of how information is processed in the brain and how this information may be extracted and interpreted. In a clinical setting, the emerging field of brain-machine interfaces has been showing promise as a therapeutic device for patients with quadriplegia brought about by spinal cord injury or motor neuron disease and this type of research provides the science backing these solutions. In 2004, it was demonstrated by our lab that signals correlating with movement intention were observed in human patients that have been paralyzed for years. This knowledge combined with monkey studies of movement planning information in the cortex quickly allowed the decoding of these signals into mouse cursor movements. The science of what information is represented in cortical signals continues to improve decoding of signals for neural prosthetics applications.
|Rao, Naveen G; Donoghue, John P (2014) Cue to action processing in motor cortex populations. J Neurophysiol 111:441-53|