Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 13, 1017
eCollection

μECoG Recordings Through a Thinned Skull

Affiliations

μECoG Recordings Through a Thinned Skull

Sarah K Brodnick et al. Front Neurosci.

Abstract

The studies described in this paper for the first time characterize the acute and chronic performance of optically transparent thin-film micro-electrocorticography (μECoG) 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 μECoG arrays. In a longitudinal chronic study, μECoG grids placed on top of a thinned skull maintain impedances comparable to epidurally placed μECoG grids that are stable for periods of at least 1 month. Optogenetic activation of cortex is also reliably demonstrated through the optically transparent μECoG grids acutely placed on the thinned skull. Finally, spatially distinct electrophysiological recordings were evident on μECoG electrodes placed on a thinned skull separated by 500-750 μm, 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.

Keywords: local field potenitals; optogenetics; somatosensory evoked potentials; thinned skull; μECoG.

Figures

FIGURE 1
FIGURE 1
(A) Diagram illustrating chronic placement of 16-channel bilateral μECoG array, and ZIF connector on thinned skull surface over sensorimotor cortex in a rat. (B) Polyimide-based platinum μECoG array with 16 channels (750 μm spacing, 250 μm site diameter). (C) Surgical photograph of bilateral parylene C-based platinum μECoG array being placed over a thinned skull (top of photograph) and on the dural surface (bottom of photograph). Scale bars in panels (B,C) represent 2 mm.
FIGURE 2
FIGURE 2
(A) Illustration of μECoG electrode array placement over a thinned skull in a mouse with optical fiber positioning. (B) Optogenetic stimulation of cortex with optical fiber placed on a μECoG array over thinned skull. (C) Parylene C-based platinum μECoG array with 16 channels (500 μm spacing, 150 μm site diameter) and ZIF connector. Scale bar in panel (C) represents 2 mm.
FIGURE 3
FIGURE 3
Somatosensory evoked potentials (SSEPs) recorded on week 3 post-implantation from a rat implanted with a 16-channel μECoG array placed on thinned skull over left sensorimotor cortex. Biphasic current pulses (1 ms, varied amplitude) were used to stimulate the right hindlimb with surface electrodes over the sciatic nerve. (A) Stainless-steel bone screw, (B) common average, and (C) small Laplacian referencing strategies are shown to increase the signal-to-noise ratio, and to reveal spatial signaling from the predicted hindlimb anatomical region. Dashed lines represent onset of electrical stimulus.
FIGURE 4
FIGURE 4
Somatosensory evoked potentials (SSEPs) on day 38 post-implantation with small Laplacian referencing from forelimb and hindlimb electrical surface stimulation using a 16-channel μECoG array placed over a thinned skull portion of rat sensorimotor cortex. Plots represent spatial recordings from the same electrode array, demonstrating LFPs from (A) biphasic forelimb stimulation and (B) monophasic hindlimb stimulation. Stimuli were applied for 1ms at 1.25 mA. Activity is represented by 2D interpolated heat maps. The portions closer to the red spectrum show evoked activity higher than baseline when averaged over at least 25 trials, and closer to blue shows negative activity. The x scale bar, 20 ms; y scale bar, 20 μV. Dashed lines represent onset of electrical stimulus.
FIGURE 5
FIGURE 5
Chronic impedance spectral data at 1 kHz from thinned skull (blue) and epidurally (red) implanted μECoG electrodes in rats. Each interpolation curve represents three animals per group, and 32 electrode sites per animal. Individual data points represent individual electrode site impedance spectra measurements. Each shape represents an individual animal. Epidural impedances increase until ∼2 weeks and plateau, while thinned skull impedances remain lower and more stable.
FIGURE 6
FIGURE 6
Optically evoked local field potentials from (A) thinned skull and (B) epidurally implanted μECoG arrays in an acute, terminal Thy1-ChR2 mouse. Amplitude heat maps show the 545.5 mW/mm2 optically evoked potentials using small Laplacian referencing from both the (C) thin skull and (D) epidural preparations. Each can be processed to illustrate the spatial resolution of the recordings, although the difference in scale is smaller in the thinned skull preparation by approximately a magnitude of 10. Dashed lines represent onset of electrical stimulus.
FIGURE 7
FIGURE 7
Photostimulus duration vs. amplitude peak potential 2D interpolated contour plot. Stimulus strength is plotted against stimulus duration. Interpolated curves denoting the peak depolarization amplitudes (in μV) for the stimulus strength/duration are shown for (A) epidural and (B) thinned skull μECoG recordings in an acute terminal Thy1-ChR2 mouse. Longer stimulus durations and stimulus strength (power) are needed to evoke similar sized neural signal amplitudes in the thinned skull vs. epidural preparations. The stainless-steel skull screw reference was used for this analysis. No additional software referencing techniques were used.

Similar articles

See all similar articles

References

    1. Akhtari M., Bryant H. C., Mamelak A. N., Flynn E. R., Heller L., Shih J. J., et al. (2002). Conductivities of three-layer live human skull. Brain Topogr. 14 151–167. - PubMed
    1. Bazley F. A., Hu C., Maybhate A., Pourmorteza A., Pashai N., Thakor N. V., et al. (2012). Electrophysiological evaluation of sensory and motor pathways after incomplete unilateral spinal cord contusion. J. Neurosurg. Spine 16 414–423. 10.3171/2012.1.SPINE11684 - DOI - PubMed
    1. Bonder D. E., McCarthy K. D. (2014). Astrocytic Gq-GPCR-Linked IP3R-Dependent Ca2+ signaling does not mediate neurovascular coupling in mouse visual cortex in vivo. J. Neurosci. 34 13139–13150. 10.1523/JNEUROSCI.2591-14.2014 - DOI - PMC - PubMed
    1. Degenhart A. D., Eles J., Dum R., Mischel J. L., Smalianchuk I., Endler B., et al. (2016). Histological evaluation of a chronically-implanted electrocorticographic electrode grid in a non-human primate. J. Neural. Eng. 13:046019. 10.1088/1741-2560/13/4/046019 - DOI - PMC - PubMed
    1. Drew P. J., Shih A. Y., Driscoll J. D., Knutsen P. M., Blinder P., Davalos D., et al. (2010). Chronic optical access through a polished and reinforced thinned skull. Nat. Methods 7 981–984. 10.1038/nmeth.1530 - DOI - PMC - PubMed

LinkOut - more resources

Feedback