So far, the work has been focused towards the following objectives:
i) Develop electronic technologies for brain mapping to record from large number of active sites over large areas of the cortex. We have been developing the technology roadmap. The g-SGFET technology has reached high maturity, reaching very yields over 80% and high homogeneity, and reducing the 1/f electronic noise; we have validated in vitro and in vivo the recording capabilities of g-SGFETs; we have performed an in vitro assessment of g-SGFETs devices (8×8 arrays) for multiplexing strategies. We have successfully validated: (i) 2 different multiplexing strategies with arrays of 8×8 g-SGFET in acute in vivo experiments using discrete electronics, and (ii) the g-SGFETs in an in vivo chronic setting using a wireless headstage.
A first ASIC has been full-custom designed for a novel switch-less multiplexing strategy of g-SGFET arrays. The design of a 1024-channel ASIC with digital output for the switch-less multiplexing of 32×32-arrays of GFET sensors has been completed and is currently being fabricated.
ii) Advance the fundamental understanding of the link between surface and intracortical signals and dynamics in cortical circuits. We have developed flexible cranial interface and performed first of a kind distributed recordings together with 3D behaviour, and a Green-function-based frequency domain procedure for LFP decomposition, and we have identified sparse and distributed anatomical basis for decoding of spatial representation from hippocampal LFP in theta frequency band. We have established joined depth and ECoG recordings in motor cortex combined with 3D limb analysis in locomoting head-fixed mice and identified contribution of theta dynamics to motor cortex activity; we have performed first recordings in minipigs with 256 channel wireless recording system combined with vocalization analysis.
iii) Gain new fundamental understanding of the distributed brain circuits of speech and their plastic flexibility before and after lesions. We have started to characterize the brain dynamics underlying overt and inner speech production in humans, both at the whole brain level using non-invasive, and more locally using invasive large-scale electrophysiology. We have collected several datasets in patients with ECoG electrodes for word level speech production, characterizing the covert speech network. We have also developed original decoding methods, and characterization of best neural signals to be decoded (high and low frequency signals, inter-site correlations).
iv) Development of speech BCI proof of concept. We have developed a versatile software framework to allow customizable real-time processing of any type of data streams (including neural recordings from different recording systems), incorporating real-time DNN-based speech synthesis for closed-loop BCI applications. A first closed-loop speech BCI paradigm was tested in a new epileptic patient. We developed a neuromorphic approach to perform online spike sorting that anticipates the advent of very large scale neural recordings with BrainCom implants that will need to be processed at very low-power for a wireless usage.
v) Develop a solid ethics framework to identify and explore issues linked to the use of brain implants. Collaborative research has continued on questions generated by neural decoding techniques, including the prospect for involuntary speech and inadvertent ‘mind reading’. Further work has addressed questions concerning user responsibility, control of devices, and the status of brain data.
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