Abstract
Cortical maps, which are indicative of cognitive status, are shaped by the organism’s experience. Previous mapping tools, such as penetrating electrodes and imaging techniques, are limited in their ability to be used to assess high-resolution brain maps largely owing to their invasiveness and poor spatiotemporal resolution, respectively. In this study, we developed a flexible graphene-based multichannel electrode array for electrocorticography (ECoG) recording, which enabled us to assess cortical maps in a time- and labor-efficient manner. The flexible electrode array, formed by chemical vapor deposition (CVD)-grown graphene, provided low impedance and electrical noise because a good interface between the graphene and brain tissue was created, which improved the detectability of neural signals. Furthermore, cortical map remodeling was induced upon electrical stimulation at the cortical surface through a subset of graphene spots. This result demonstrated the macroscale plasticity of cortical maps, suggesting perceptual enhancement via electrical rehabilitation at the cortical surface.
Highlights
Cortical sensory maps reflect the spatial organization of neural networks representing sensorimotor behavior and cognition and provide an accessible measure of cognitive learning enforced by experience
The low impedance can suppress electrical noise, allowing the electrode size to be scaled down and increasing the detectability of neural signals through a high signal-to-noise ratio (SNR). With these excellent characteristics of graphene multichannel electrodes for measuring neural signals, we studied cortical map plasticity over an area of several square millimeters
With a small bending radius (5 mm), the graphene electrodes still maintained their impedance value below ~ 100 kΩ. These results indicated that the graphene electrode array could conduct uniform spatial brain mapping with low noise on a nonplanar cortical surface
Summary
Cortical sensory maps reflect the spatial organization of neural networks representing sensorimotor behavior and cognition and provide an accessible measure of cognitive learning enforced by experience. The use of penetrating electrodes or liquid-filled glass micropipettes to acquire decent brain maps for brain mapping requires tremendous amounts of labor and time These techniques are invasive and damage brain tissue, preventing repetition[13]. Alternative brain-mapping tools, such as electroencephalography, positron-emission tomography, magnetoencephalography, and functional magnetic resonance imaging (fMRI), are noninvasive, enabling whole-brain mapping with repeated sampling. These methods are being increasingly used for brain mapping; they have disadvantages, such as low spatial resolution, temporal lag, errors due to unspecified modulatory inputs, and/or prohibitive costs[14,15,16]. Other options include optical techniques, such as calcium imaging and optogenetic
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