Biomedical Engineering Reference
In-Depth Information
The Intrafascicular Electrode.
Lefurge and co-workers [156] reported
their measurement of signals from the radial nerve of cats by intrafascicular
electrodes for six months. The intrafascicular electrode is a type of wire elec-
trode.Itsrecordingsiteiscreatedbyremovingsomeinsulation,bymeansof
heat, from the wires at some distance from one end, and then platinum black
is deposited in the uninsulated region. A tungsten needle is used to insert the
electrode into the nerve fascicle (Fig. 4.40).
The Tungsten Microelectrode.
In the method of microneurography
[157,158], insulated tungsten microelectrodes are used. The most typical type
of electrodes is 120-200 micro meters in diameter, and only the tip of the el-
ectrode is uninsulated. They can be inserted percutaneously into the median
nerve of awake human subjects, because the shaft is suciently rigid. Thus
they are capable of recording from and stimulating a single nerve fiber. We
use this type of electrode to stimulate the sensory nerve fiber that comes
from a cutaneous receptor and generate an artificial touch sensation [159].
However, this type of electrode is only good for acute experiments, and is
dicult to use in multi-channel interfaces.
A Summary of the Handmade Electrodes.
The handmade electrodes
mentioned above are still used as fundamental tools in a lot of basic research
areas. There are also some applications in which compound signals from the
nerve bundle are useful. Moreover, if the number of neurons in the compound
signal could be made small enough by selecting the implant position, useful
information could be extracted by suitable signal-processing methods. On
the other hand, the tungsten electrode has sucient properties to record
single unit activity, although it is limited to acute experiments. However,
these handmade electrodes have limitations in the feasibility of multi-channel
chronic interfacing, which is necessary to realize the applications mentioned
Fig. 4.40.
The intrafascicular electrode. A needle is used to insert the electrode
into the nerve fascicle
