Electrocorticography on the Micron Scale: Single Units and Enhanced Neural State Estimation

Electrocorticography on the micron scale (micro-ECoG) is an emerging neural sensing modality that provides a high-resolution view of the brain. Micron scale electrodes measure electrical potential propagated to the brain surface from local and distant current sources. Moreover, electrodes spatially sample the surface of the brain at the micron scale over potentially large regions providing both high resolution and large coverage. Micro-ECoG can be likened to HD monitors, whereas classical ECoG grids are more like Hex LED displays. In this dissertation, I demonstrate the value of micro-ECoG both in animal model and in humans. I developed a suite of neural acquisition tools (NACQ), which was used to record from human subjects intraoperatively and in the epilepsy monitoring unit for research purposes. These tools provide an affordable alternative to commercial systems and a safer alternative to existing open source systems. I demonstrate that micro-ECoG electrode can sense physiologically relevant features, including single unit activity in songbird. These physiological features measured from micro-ECoG are compared to gold standard probes including penetrating laminar silicon shanks in songbird and clinical ECoG strips in human. Finally, I explored theoretical and empirical instances in which a high density grid of electrodes outperforms sub-sampled lower density grids in discrete neural state estimation. Empirically, I show that when controlling for area and selecting task informative sub-regions of the complete grid, we observed a consistent increase in mean binary classification accuracy with higher grid density; in particular, 400 μm pitch grids outperforming spatially sub-sampled lower density grids up to 23%. Micro-ECoG is a promising neural sensing modality that may lead to new neuroscientific discoveries and neuroengineering achievements. For example, it may uncover novel neural dynamics from cortical columns or intricate cortical wave patterns important from neural information processing. Micro-ECoG may lead to the development of a high-bandwidth brain machine interface that not only restores abilities of disabled individuals, but augments and enhances abilities of able-bodied people. Neuroscientists and neurotechnologists are poised to make major advances in neuroscience and neuroengineering with the advent of micro-ECoG