Ground surface configuration for focal
extracellular electrical stimulation of a
living tissue
CONTEXT
Notre référence :
01131-01
Status des brevets
French patent
application FR0707369
filed on October 22nd,
2007
entitled "Configurations
de matrices de
microélectrodes pour
une stimulation focale
d'un tissu vivant"
Inventeurs
Blaise YVERT
Sébastien JOUCLA
Lionel ROUSSEAU
Status Commercial
Exclusive or nonexclusive licenses,
Collaborative
agreement
Laboratoires
Institute for Cognitive
and Integrative
Electrical extracellular stimulation of the nervous system has been used empirically for
several decades, with peripheral nerve, cochlear, deep brain, or spinal cord stimulation
paradigms used routinely to find rehabilitation strategies or alleviate symptoms in case of
neurological disorders such as neuropathic pain, hearing loss, movement disorders,
Parkinson disease, or epilepsy. Nowadays, electrical microstimulation using
microelectrode arrays (MEAs) undergoes a strong interest for the development of refined
neural prosthesis, such as retinal, sub-cortical or cortical implants relying on the precise
activation of localized neuronal pools. An important issue for achieving the best efficacy of
such device is thus to achieve a precise control of the spatial extent of electrical stimuli.
Although multipolar configurations combining several electrodes can yield more focal
stimulations than classical monopolar stimulations, they are difficult to implement in the
case of high-density MEAs due to the number of electrode combinations to handle. For
this reason, currently most microstimulation approaches using MEAs (e.g., clinical trials
retinal implants) still rely on monopolar stimulations despite their lack of spatial selectivity.
TECHNICAL DESCRIPTION
Here, we propose a new electrode configuration that improves the focality of electrical
stimulation without the need to consider multipolar electrodes. The idea of this
configuration consists in introducing a ground surface surrounding all the electrodes of the
array, which ensures the return of the current i delivered by any of the electrodes: This
ground surface can be embedded in either planar MEAs (Figure A, top scheme, for details
see Joucla and Yvert, 2009) or penetrating probes (Figure B, top scheme, for details see
Joucla et al., 2012) for either in vitro or in vivo applications. With this approach, stimulation
focality is much higher than with the classical monopolar configuration (M, black, in bottom
panels) or with in concentric configuration (CB, gray, bottom left panel).
Neuroscience (INCIA),
UMR5287, in Talence,
France.
Mots clés :
Electrical neural
stimulation Electrical
microstimulation
Functional electrical
stimulation Stimulating
device Microelectrodes
Microelectrode Array
(MEA) Implants Neural
probes Neural
Prostheses BrainComputer Interfaces
Brain-Machine
Interfaces Stimulation
Focality Stimulation
Threshold Central
Nervous System (CNS)
Periheral Nervous
System Motor System
Sensory Systems, Brain
Cortex, Spinal Cord
Retina Cochlea Nerves,
Muscles Heart Muscular
system Cardiovascular
system
Moreover, stimulations are all the more focal that the surface conductance of the ground
surface with respect to the extracellular medium is high. This better focalization is shown
in the above figures by the profiles of electrical potential field obtained for surface
conductance of increasing values, starting from a few hundred of S/m2, corresponding to
the surface conductance of Platinum at 1 kHz, to several hundreds of S/m2,
corresponding to low-impedance porous materials such as black platinum, carbon
nanotubes or conductive polymers.
The figure below shows two realizations of this ground surface configuration for in vitro
MEAs (A) and for a penetrating probe (B). In the first case, the ground surface is a grid
surrounding the electrodes. In the second case, the ground surface is a plane.
The modeling predictions shown above were confirmed experimentally in the case of a
simple non porous ground surface, already providing a better focality of the potential
field than a monopolar configuration (Rousseau et al., 2009).
Importantly, regarding microfabrication, the realization of this configuration does not bring
significant additional costs for it requires only one subsequent mask.
BENEFITS
Beyond the benefit that it does not require the combination of multiple electrodes, another
important practical advantage of the proposed configuration is the trade-off it offers
between stimulation focality and required current. Indeed, better focality can be achieved
with currents less than twice those required by a monopolar configuration, while much
stronger currents (about 20 times stronger) are needed with a concentric bipolar
configuration (Joucla and Yvert, 2009). This gain in current amplitude is important to
reduce electrode deterioration and to achieve low-consumption implantable devices for
which battery life is an important practical issue.
INDUSTRIAL APPLICATIONS
In vitro microelectrode arrays, in vivo neural probes, clinical neural prostheses and
implants (e.g., deep brain, cochlear, retinal, spinal cord, or cortical implants), braincomputer interfaces.
DEVELOPMENT STAGE
Prototypes of ground surface configurations have been realized for in vitro or in vivo
applications. First prototypes have also been achieved on flexible substrates. As shown in
the first figure above, stimulation focality is best for highest conductance of the ground
surface. Current developments thus focus on the achievement of very low impedance
materials (Heim et al., 2012) for the ground surface.
PUBLICATIONS
Joucla S, Yvert B. (2009) Improved focalization of electrical microstimulation using
microelectrode
arrays:
a
modeling
study.
PLoS
One,
4(3):
e4828.
doi:10.1371/journal.pone.0004828.
Rousseau L, Joucla S, Lissorgues G, Yvert B. (2009) Microfabrication of new
microelectrode arrays equipped with a ground surface configuration for focal neural
microstimulation.
J
Micromech
Microeng,
19
–
074010,
doi:10.1088/0960-1317/19/7/074010.
Joucla S, Rousseau L, Yvert B. (2012) Focalizing electrical neural microstimulation with
penetrating microelectrode arrays: a modeling study. J Neurosci Methods, 209(1):250-4.
Heim M, Rousseau L, Reculusa S, Urbanova V, Mazzocco C, Joucla S, Bouffier L,
Vytras K, Bartlett P, Kuhn A, Yvert B. (2012) Combined macro-/mesoporous
microelectrode arrays for low-noise extracellular recordings of neural networks. J
Neurophysiol, 108(6):1793-803.
For further information, please contact us (Ref 01131-01)
Powered by TCPDF (www.tcpdf.org)