A hybrid micro-ECoG for functionally targeted multi-site and multi-scale investigation

Brain function relies on the coordination of activity across a wide range of spatial and temporal scales. The activity of single neurons depends on their unique pattern of local and long-range connectivity and thus on the coordination of local activity with large-scale patterns of distributed activity across brain-wide networks. Understanding integrated, whole brain function requires new tools capable of recording from anatomically connected populations in distributed brain areas to bridge local and global dynamics. Here, we present high-density, micro-electrocorticography arrays that facilitate multi-scale studies of brain activity. The arrays are hybrid designs that integrate the desirable features of silicone elastomers and polyimide films. The silicone elastomer superstructure provides optical transparency and permits repeated mechanical penetration with rigid linear electrode arrays. The polyimide films provide the capacity for fine feature definition through photolithography. This combination facilitates high-throughput functional mapping of areas of interest to target functionally characterized populations for refined, dense sampling. We demonstrate the suitability of the technique for functional mapping of cortical regions in rats, cats and marmosets and the benefit of the resulting functional maps for targeting functionally defined populations for dense, multi-area laminar recordings. Finally, we demonstrate the utility of the hybrid {micro}ECoG to localize optogenetically evoked feedforward excitation in down-stream cortical regions to investigate cortico-cortical interactions. Together, these capabilities make the hybrid {micro}ECoG a compelling tool for systems neuroscience.