Transparent electrode arrays for visualization, simultaneous imaging, and electrophysiology

Calcium imaging is a versatile tool capable of resolving single neurons and their connectivity with single-cell spatial resolution in the brain. Unfortunately, its coarse temporal resolution limits its ability to detect neural activity with a single spike resolution.

Electrophysiological recordings provide high temporal, but limited spatial resolution, due to the dense 3D architecture and geometrical inaccessibility of the brain.

An approach that integrates the advantages of both techniques could provide new insights into functions of neural circuits.

The Litt Lab has developed a transparent and flexible electrode array that contains graphene electrodes. This electrode array enables simultaneous optical imaging of biological tissue, with high signal-to-noise ratio recordings of electrophysiological activity. Specifically, graphene electrodes provide low electrical noise, which can lead to sensor technologies with increased sensitivities that may enable detection of individual molecules. Graphene also provides flexibility and protection against corrosion, and is optically transparent at wavelengths useful for optical imaging.

Transparent graphene electrodes can simultaneously record neural activity during calcium imaging with confocal or multi-phone microscopy without any laser-induced artifacts in the recordings.

Combination of both techniques has shown temporal and spatial characteristics of high frequency bursting activity and synaptic potentials in hippocampal slices with high precision. 

• Electrodes and wires are all optically transparent.
• The graphene electrode has a maximum dimension ranging from 50-500μm.
• Provides a method for simultaneous optical imaging and electrical sensing