A modular high-density 294-channel μECoG system on macaque vlPFC for auditory cognitive decoding

Abstract

OBJECTIVEA fundamental goal of the auditory system is to parse the auditory environment into distinct perceptual representations. Auditory perception is mediated by the ventral auditory pathway, which includes the ventrolateral prefrontal cortex (vlPFC) late. Because large-scale recordings of auditory signals are quite rare, the spatiotemporal resolution of the neuronal code that underlies vlPFCs contribution to auditory perception has not been fully elucidated. Therefore, we developed a modular, chronic, high-resolution, multi-electrode array system with long-term viability.\n\nAPPROACHWe molded three separate ECoG arrays into one and implanted this system in a non-human primate. A custom 3D-printed titanium chamber was mounted on left hemisphere. The molded 294-contact ECoG array was implanted subdurally over vlPFC. ECoG activity was recorded while the monkey participated in a \"hearing-in-noise\" task in which they reported hearing a \"target\" vocalization from a background \"chorus\" of vocalizations. We titrated task difficulty by varying the sound level of the target vocalization, relative to the chorus (target-to-chorus ratio, TCr).\n\nMAIN RESULTSWe decoded the TCr and the monkeys behavioral choices from the ECoG signal. We analyzed decoding capacity as a function of neuronal frequency band, spatial resolution, and time from implantation. Over a one-year period, we were successfully able to record ECoG signals. Although we found significant decoding with as few as two electrodes, we found near-perfect decoding with [~]16 electrodes. Decoding further improved when we included more electrodes. Finally, because the decoding capacity of individual electrodes varied on a day-by-day basis, high-density electrode arrays ensure robust decoding in the long term.\n\nSIGNIFICANCEOur results demonstrate the utility and robustness of high-resolution chronic {micro}ECoG recording. We developed a new high-resolution surface electrode array that can be scaled to cover larger cortical areas without increasing the chamber footprint.