non-Pacinian channel I (NP I channel), generally mediating thresholds
from 10 to 40 Hz, and the Pacinian channel having a U-shaped
contour of displacement sensitivity over the frequency range
40–800 Hz with maximum sensitivity to displacement around 250
or 300 Hz [4–7].
Thresholds for the perception of vibration at the thenar eminence
on the hand decrease at a rate of 3 dB per doubling of contact
area (from 0.02 to 2.9 cm2) at frequencies from 80 to 320 Hz, but
not at 25 and 40 Hz [2]. The different effects of contact areas at
different frequencies are attributed to the differing properties of
the channels mediating the perception of vibration. The Pacinian
channel (i.e., P channel) has the property of spatial summation,
whereas the NP I channel has no spatial summation [2–4]. When
the contact area at the thenar eminence was sufficiently reduced
(from 0.02 cm2 to 0.005 cm2), there was no evidence of spatial summation
at frequencies greater than 80 Hz [2]. Further studies have
found that the perception of vibration with very small contact areas
is determined by the non-Pacinian II channel (i.e., NP II channel),
which does not have the property of spatial summation [5,6].
Spatial summation has also been observed at the fingertips.
Gescheider et al. [7] obtained vibrotactile thresholds with probe
contact areas of 0.025, 0.10, 0.38, and 0.75 cm2 at the fingertip. With
300 Hz vibration, thresholds reduced with a slope of 3 dB per doubling
of contactor area between 0.025 and 0.10 cm2 (probes with
non-Pacinian channel I (NP I channel), generally mediating thresholdsfrom 10 to 40 Hz, and the Pacinian channel having a U-shapedcontour of displacement sensitivity over the frequency range40–800 Hz with maximum sensitivity to displacement around 250or 300 Hz [4–7].Thresholds for the perception of vibration at the thenar eminenceon the hand decrease at a rate of 3 dB per doubling of contactarea (from 0.02 to 2.9 cm2) at frequencies from 80 to 320 Hz, butnot at 25 and 40 Hz [2]. The different effects of contact areas atdifferent frequencies are attributed to the differing properties ofthe channels mediating the perception of vibration. The Pacinianchannel (i.e., P channel) has the property of spatial summation,whereas the NP I channel has no spatial summation [2–4]. Whenthe contact area at the thenar eminence was sufficiently reduced(from 0.02 cm2 to 0.005 cm2), there was no evidence of spatial summationat frequencies greater than 80 Hz [2]. Further studies havefound that the perception of vibration with very small contact areasis determined by the non-Pacinian II channel (i.e., NP II channel),which does not have the property of spatial summation [5,6].Spatial summation has also been observed at the fingertips.Gescheider et al. [7] obtained vibrotactile thresholds with probecontact areas of 0.025, 0.10, 0.38, and 0.75 cm2 at the fingertip. With300 Hz vibration, thresholds reduced with a slope of 3 dB per doublingof contactor area between 0.025 and 0.10 cm2 (probes with
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