Biomedical Engineering Reference
In-Depth Information
Fig. 4.56.
The manner in which the experiment for the measurements and stimu-
lations were performed. The position of the inserted electrode was fixed so that it
allowed recording and stimulation of a single nerve fiber from a single mechanore-
ceptor unit
movement; these receptors are suitable for detecting slow vibrations whose
frequency is less than 40 Hz.
The Pacinian type shows very sensitive responses and very fast adapta-
tion to the stimuli and corresponds to the signals from Pacinian corpuscles,
which detect the acceleration of the skin movement; this type of receptor is
suitable for detecting vibration.
Ochoa et al. have reported that a pressure sensation is evoked by stimu-
lating an SA I mechanoreceptor unit, and that the magnitude of the evoked
sensation is influenced by the frequency of the stimulus but not by the am-
plitude of the stimulus [188].
Our results basically confirm the results reported by Ochoa et al. With
respect to sensory nerve fibers from the SA I mechanoreceptor unit, our re-
sults showed that the electrical microstimulation evoked pressure sensations,
and that the magnitude of the evoked sensation increased with the stimulus
frequency and seemed to be a positive power of the frequency (Fig. 4.59).
This type of response is often observed in the field of sensation, as in the case
of the relationship given by the Weber-Fechner law or Stevens's law.
Combined Evoked Sensation due to the Simultaneous Electrical
Stimulation of Multiple Single Mechanoreceptor Units.
So far, we
have mentioned the methods of evoking artificial sensation by electrically sti-
mulating a single mechanoreceptor unit. However, when we actually touch
something, it is impossible for only one mechanoreceptor unit to be stimu-
lated; in fact, both a large number and various kinds of nerve fibers are
