Acute electrocorticographic signal recording at the operating room

Evidence from electrophysiological studies suggests that brain functions are a
result of the connectivity between collections of neurons performing specific
tasks, so-called neural ensembles or functional units. In the last decades, an
increasing number of papers have been published on the neurophysiological
underpinnings of human cognition and behavior at this level of detail, in
particular using electrode grids (silicon sheets with embedded platinum discs)
positioned under the dura in surgery patients. This technique, named
electrocorticography or ECoG, has empowered the study of neurophysiological
mechanisms and consequently improved the treatment of neurological and
psychiatric brain disorders. At the UMC Utrecht, a combination of favorable
factors such as 1) the excellent reputation in research on brain function
involving implanted ECoG grids in the epilepsy surgery program, 2) the
increasing number of surgeons at the UMC who are skilled in awake surgery (now
4), and 3) the increasing number of performed awake surgeries in the last years
(50+ per year), has reinforced the fact that intraoperative recordings (awake
and sleep) are a unique opportunity for research on brain function. In the last
four years, we have conducted a pilot study with high-density ECoG grid
recordings in epilepsy and tumor patients during awake surgeries (approved MREC
14-622). We introduced small high-density ECoG grids as a tool to study the
detail of functional units. These grids promise to extract more detailed
information from a smaller patch of the human cortex, potentially providing an
advance in the field of human cognition and behaviour. In the pilot study we
have determined whether awake surgery on patients with a brain tumor or other
lesions allows for ECoG data collection of adequate quality to address research
questions, which yielded exceptionally encouraging results. Optimal
investigation of human brain functions at that level of detail is only feasible
with highly resolved ECoG grids and is essential to increase the understanding
about the human brain and can contribute to future improvement of
neurotechnology devices, such as Brain Computer Interfaces (BCIs) and possibly
in the long-run close-loop deep-brain stimulation systems.

In the current study we expand on the knowledge previously learned in the pilot
study and address a wider range of neuroscientific questions related to brain
electrophysiological and hemodynamic responses. Because of the rarity and
richness of this type of data we will combine multiple objectives in one study,
such that we can efficiently address multiple research questions using one
single setup. The main goal of this study is, therefore, to use high-density
ECoG grids to address two main objectives:
1. Investigate the possibilities for high-dimensional brain decoding for
ECoG-based Brain Computer Interfaces (BCIs);
2. Assess the precise relationship between hemodynamics and neuronal activity;

Subjects are included in an observational study, which includes intraoperative
ECoG recordings with a high-density grid, intraoperative optical imaging and
pre- or post-surgery structural and functional Magnetic Resonance Imaging (MRI,
fMRI) scans.

During the surgery we will ask the neurosurgeon to temporarily position a
high-density electrode grid on exposed or closely accessible brain surface, at
a time that is convenient. ECoG grids are frequently used during epilepsy
surgery and there are no known risks associated with their intraoperative use.
All hardware used for the ECoG recordings is CE or MTKF certified and is safe.
The ECoG measurements are not required for the surgery. There is no immediate
benefit to the participants. There are no known risks associated with
intraoperative optical imaging and pre- or post-surgical MRI/fMRI acquisition.
Intraoperative ECoG and/or optical recordings may slightly increase the
duration of surgery (several minutes). Including all procedures, the burden can
be considered minimal.*