Biomedical Engineering Reference
In-Depth Information
g
K
K
+
conductance
g
L
Leak conductance
g
Na
N a
+
conductance
MWNT
Multi-walled carbon nanotube
R
a
Axial cytoplasmic resistance
R
cnt
CNT equivalent resistance
R
in
Amplifi er input resistance
R
s
Seal resistance
R
sp
Spread resistance
SWNT
Single-walled carbon nanotube
V
cnt
CNT potential
V
m
Membrane potential
1
Introduction
Translating basic neuroscience research into experimental neurology applications
often requires functional interfacing of the central nervous system (CNS) with arti-
fi cial devices designed to monitor and/or stimulate brain electrical activity. Ideally,
such interfaces should provide a high temporal and spatial resolution over a large
area of tissue during stimulation and/or recording of neuronal activity, with the
ultimate goal to elicit/detect the electrical excitation at the single-cell level and to
observe the emerging spatiotemporal correlations within a given functional area.
Activity patterns generated by CNS neurons have been typically correlated with a
sensory stimulus, a motor response, or a potentially cognitive process.
The growing interest in interfacing CNS structures to artifi cial devices is related
to the possible improvements in our ability to decode and interpret brain signals. This
achievement might be of critical importance not only for elucidating how the brain
works, but also to reach a control of prosthetic devices by pure thought. The progress
in neuronal activity recording and/or stimulation strongly relies on the optimization
of neuron-electrode functional interface, transducing ion fl uxes related to neuronal
electrical activity into electron fl uxes within the electrode-conducing material. Such
a functional coupling has been traditionally achieved by means of metal electrodes,
which allow variable degrees of neuronal target selectivity, signal sensitivity, and
recording distortions. The ongoing amelioration of these important features is addressed
by optimizing the mechanical and physical properties of the electrodes.
In basic neuroscience research, the application of neuronal recordings contrib-
uted a great deal to the global comprehension of CNS operation, and each technical
achievement or improvement has been rewarded by signifi cant scientifi c discover-
ies. For instance, advances in recording technologies, such as the development of
the glass micropipette, have provided researchers with excellent and cheap trans-
duction interfaces whose size matches that of subcellular structures. This has
allowed the quantitative study of the ionic basis of nerve transmission. Thus,
although the evolution of electrode/CNS interfaces is likely to remain driven by
