82 References
will alleviate the tissue reaction. Surface modification of electrodes with anti-
inflammatory compounds
102
appears to lessen the glial encapsulation, but some
gliosis is still present, so research in electrode surface modification remains an
important topic for the realization of successful chronic neural electrodes.
The insertion of probes into the brain can be done quickly or slowly. Faster in-
sertion speeds and sharper needles result in less strain to the surrounding tissue.
103
This reduced strain may minimize tissue damage due to insertion, because pro-
cesses and cells near the electrode remain relatively undisturbed while those in
the electrode’s path are completely severed.
92
However, some investigators insist
that slower insertions lead to greater longevity in chronic recordings.
104
This may
be because slow insertions allow cells and their processes time to be displaced and
moved, rather than impaled, by microelectrodes.
92
Insertion technique is far from
standardized in the neural interfacing fields, and no one technique may be best for
all MEMs devices, so insertion method will probably continue to be chosen on a
device-by-device basis.
4.4 CONCLUDING REMARKS
MEMs devices hold immense promise for future neuroprosthetics and inves-
tigative biological studies. In vitro devices allow the observation of individual
cell types and their reactions to environmental stimuli; the small volumes used,
inexpensive materials, and ability to batch fabricate devices reduces the cost to
perform such studies. In vivo microdevices are less damaging to neural tissues
than larger devices, some can be batch fabricated, and most are electrically or
chemically active. Such devices may one day allow patients who have lost normal
neural function to regain it.
Neuronal interfacing technology is far from completely optimized, but new
developments are always refining existing processes and opening new frontiers.
The implications for improved understanding of the nervous system and the
ability to improve patient quality of life are some of the strongest factors driving
thefieldtoday,andbecausethepromiseisevident,wecanexpecttoseeimportant
strides being made towards seamless integration of sensor and actuator technol-
ogy with the human nervous system in the future.
References
1
Nisch, W., et al., A thin-film microelectrode array for monitoring extracellular neuronal-
activity in vitro. Biosensors & Bioelectronics, 1994, 9(9–10): 737–741.
2
Wagenaar, D. A., J. Pine, and S. M. Potter, An extremely rich repertoire of bursting
patterns during the development of cortical cultures. BMC Neuroscience, 2006, 7: p.17.
3
Hammerle, H., et al., Extracellular recording in neuronal networks with substrate
integrated microelectrode arrays. Biosensors & Bioelectronics, 1994, 9(9–10): 691–696.
4
Meister, M., J. Pine, and D. A. Baylor, Multi-neuronal signals from the retina: Acquisi-
tion and analysis. Journal of Neuroscience Methods, 1994. 51: 95–106.
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