Brain states such as sleep, anesthesia, wakefulness, or coma are characterized by specific patterns of cortical activity dynamics, ranging from local circuits to whole-brain emergent properties. We have previously demonstrated that full-spectrum signals, including infraslow components (DC, direct-coupled), can be recorded acutely at multiple sites using flexible arrays of graphene solution-gated field-effect transistors (gSGFETs). Here, we performed chronic implantation of a 16-channel gSGFET array in the rat cerebral cortex and recorded full-band neural activity for two purposes. (1) Test the long-term stability of the implanted device. (2) Examine full-spectrum activity during transitions across different anesthesia levels. First, we show that chronic epithelial gSGFET implants can be used to record full-band signals with stability, fidelity, and spatiotemporal resolution for up to 5.5 months. Second, brain states produced by gradual changes in anesthesia levels can be identified, from synchronous slow oscillations in deep anesthesia to asynchronous activity in the awake state, traditionally using high-pass filtered (AC, alternating-coupled) spectrograms. However, DC signals have led to very significant improvements in brain state identification. The DC band provided a nearly linear informative prediction of anesthesia depth with a precision of approximately 85% using the trained algorithm. The accuracy of this prediction increased to approximately 95% when considering the full-band (AC + DC) spectrogram. We conclude that recording infrared activity using a gSGFET interface is superior for brain state identification and further supports the preclinical and clinical use of graphene neural interfaces for long-term recording of cortical activity.
Chronic full-band recordings with graphene microtransistors as neural interfaces for discrimination of brain states
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