Abstract
Currently, the brain-computer interface (BCI) field has demonstrated two distinct device strategies - macroelectrodes
(e.g., surface grids and depth) versus microelectrode arrays, and some are even pushing the field to
smaller, higher density arrays hoping to address the general signal degradation. Both approaches have been in
development for decades. However, BCI devices to treat aphasia, dysarthria, or locked-in syndrome also need
to access deeper brain regions given the very large, parallel networks involved in speech. Consider that two-thirds
of the cortex is buried beyond the reach of most state-of-the-art technologies.
We have designed a novel approach to brain recordings to address the challenge of multi-scale recordings at
any desired depth. Our team presents a novel device whose form is based on the proven safety and utility of the
stereo-EEG (SEEG). We created a directional and scalable local field potential array (DISC) using the
phenomenon of "substrate shielding". This is not the first combination micro/macro device but is the first to
demonstrate stereo-local field potentials using a patent pending design. Our preliminary in vivo data
demonstrates significant improvement when using DISC in many critical factors predictive of future BCI
performance: (i) signal amplitude, (ii) signal-to-noise ratio, and (iii) source separation in classification tasks. This
project will allow us to safely test word decoding performance both offline and online in epilepsy volunteers from
speech regions.
The project's first aim is to develop a robust DISC hybrid assembly with 128 or more recording channels per
implant. Each implanted device will be a commercially available SEEG combined with microelectrodes without
any modification to the clinical function of the device. Aim 1 will include verification, validation, biocompatibility,
and electrical safety testing. Aim 1 will also include functional and safety studies in animals to complete our effort
to provide a safe, reliable system prior to human feasibility studies.
After all milestones are met, including receiving an FDA investigational device exemption, this novel recording
system will demonstrate the effect size and variance of word and speech decoding in humans as compared with
conventional ring electrodes. Typically, 12-20 depth arrays are used in epileptogenic monitoring and we will
replace two depth electrodes with a DISC hybrid assembly in 8 experimental patients and compare decoding
performance to the within-patient controls and with a separate 8 patients having SEEG electrodes only. Enrolled
volunteers will conduct overt and covert speech tasks. Positive results will inform and enable a word and speech
decoder for persons suffering from locked-in syndrome and eventually non-fluent aphasia.