μECoG Recordings Through a Thinned Skull.

The studies described in this paper for the first time characterize the acute and chronic performance of optically transparent thin-film micro-electrocorticography (mu ECoG) grids implanted on a thinned skull as both an electrophysiological complement to existing thinned skull preparation for optical recordings/manipulations, and a less invasive alternative to epidural or subdurally placed mu ECoG arrays. In a longitudinal chronic study, mu ECoG grids placed on top of a thinned skull maintain impedances comparable to epidurally placed mu ECoG grids that are stable for periods of at least 1 month. Optogenetic activation of cortex is also reliably demonstrated through the optically transparent mu ECoG grids acutely placed on the thinned skull. Finally, spatially distinct electrophysiological recordings were evident on mu ECoG electrodes placed on a thinned skull separated by 500-750 mm, as assessed by stimulation evoked responses using optogenetic activation of cortex as well as invasive and epidermal stimulation of the sciatic and median nerve at chronic time points. Neural signals were collected through a thinned skull in mice and rats, demonstrating potential utility in neuroscience research applications such as in vivo imaging and optogenetics.