Biomedical Engineering Reference
In-Depth Information
4.7
Microneurography: Measurements and Stimulation
of a Single Peripheral Nerve Fiber
4.7.1
Introduction
One of the most important key techniques used in our research (the genera-
tion of artificial sensations by microstimulation [138] and the control of an
artificial heart system using sympathetic signals [139]) is microneurography
or microstimulation. This is probably the only technique that allows recor-
ding of the activities of a single sensory nerve fiber or stimulation of a single
sensory nerve fiber of a human subject who is awake.
In this chapter, we will briefly explain the techniques for microneurogra-
phy and microstimulation, which basically use the same procedure.
4.7.2
The History of Microneurography
Microneurography was developed by Hagbarth and Vallbo [140] in Uppsala,
Sweden, in the late 1960s. The technique makes use of a very thin tung-
sten microelectrode that is inserted into a peripheral nerve percutaneously
to measure the signals of the nerve fibers attached to the tip of the electrode.
Microstimulation of the nerve fiber, but not recording of the signal of the
nerve fiber, can be performed with the same microelectrode.
Initially, this technique was used to record the activities of Ia afferent
nerve fibers from a muscle spindle, which helped demonstrate the existence
of
α
-
γ
linkage in voluntary muscle contraction by showing that the activities
of the Ia fibers were altered in accordance with the degree of extension of
the involved muscle [141]. Next, the technique was applied to record the
activities of sensory nerve fibers and those of sympathetic nerve fibers (e.g.,
Toreb jork and Wallin [142]). This allowed analyses of the response of a single
sensory nerve fiber to stimulation of the involved mechanoreceptor unit and
contributed to classify the kinds of mechanoreceptors according to the speed
of adaptation or the pattern of the response to the given stimulation [143].
With respect to sympathetic nerve activities, the technique allowed for the
classification of skin (activities of the vasomotor and sudomotor functions)
and muscle sympathetic nerve activity (activities that control the tonus of
the vessels in the involved muscle), and a vast amount of research has focused
on these two sympathetic activities [142,144].
There have been far fewer studies on “microstimulation,” which uses ins-
erted microelectrodes for stimulating nerve fibers [145,146], than on recording
nerve activities.
Thus, microneurography has achieved excellent results in the field of basic
medical science. In the clinical field as well, many attempts have been made
to elucidate the pathophysiology of neurological diseases by recording the
activities of the involved nerves, although the technique has not yet been
used as a method of medical treatment.
