Polymer skulls with integrated transparent electrode arrays for cortex-wide opto-electrophysiological recordings

Abstract

Electrophysiological and optical imaging provide complementary neural sensing capabilities – electrophysiological recordings have the highest temporal resolution, while optical imaging allows recording the activities of genetically defined populations at high spatial resolution. Combining these complementary, yet orthogonal modalities to perform simultaneous large-scale, multimodal sensing of neural activity across multiple brain regions would be very powerful. Here we show that transparent, inkjet-printed electrocorticography (ECoG) electrode arrays can be seamlessly integrated with morphologically conformant transparent polymer skulls for multimodal recordings across the cortex. These ‘eSee-Shells’ were implanted on transgenic mice expressing the Ca2+ indicator GCaMP6f in cortical excitatory cells and provided a robust opto-electrophysiological interface for over 100 days. eSee-Shells enable simultaneous mesoscale Ca2+ imaging and ECoG acquisition under anesthesia as well as in awake animals presented with sensory stimuli. eSee-Shells further show sufficient clarity and transparency to observe single-cell Ca2+ signals directly below the electrodes and interconnects. Simultaneous multimodal measurement of cortical dynamics reveals changes in both ECoG and Ca2+ signals that depend on the behavioral state.

Fully Desktop Fabricated Flexible Graphene Electrocorticography (ECoG) Arrays

“…As an alternative, photonic sintering can be used instead of thermal annealing, allowing the use of other materials as substrates. For instance, the electrodes could be patterned on transparent polymers such as polyethylene terephthalate (PET) to create devices for simultaneous imaging and ECoG recording [11]. Though transparent graphene ECoG has been developed, it still requires cleanroom equipment [49].…”

“…Several directions can be pursued in the future, building upon the graphene ECoG devices presented in this work. The size of the implant can be extended to much larger regions of the brain [26], [27] so that the whole visual cortex and motor cortex can be included for performing ECoG recording over most of the cortical surface of the mouse brain [11]. The low and stable impedance of the electrodes can be leveraged for precise cortical micro-stimulation [14].…”

“…To simplify the fabrication procedure, inkjet printing conductive materials such as silver nanoparticle inks [9] and conductive polymers like PEDOT:PSS [10] has been used to create flexible and reconfigurable ECoG electrode arrays. Currently, these approaches require expensive printers and still rely on specialized or microfabrication techniques to insulate the electrode [11].…”

Transparent, Low‐Impedance Inkjet‐Printed PEDOT:PSS Microelectrodes for Multimodal Neuroscience

“…[51] The integration of these microelectrodes into such cranial windows has proven to be a reliable, chronically implantable interface for simultaneously monitoring ECoG and calcium fluorescence signals in transgenic mice, allowing the relationship between these modalities to be studied. [39] 2.5. Future Outlook…”

“…These ring-shaped electrodes have also been shown in separate experiments to be reliable during chronic implantations, allowing them to be used in longitudinal studies of multimodal dynamics. [39] 2. Results and Discussion…”