The name is absent

21

The qualitative percept of stimulation was akin to holding a ringing cell phone
set to "vibrate" mode, without any accompanying auditory percept. The vibration of the
benders was inaudible because of its low sound pressure level, the high ambient noise
of the MR scanner, and the hearing protection sound reducers worn by the subjects.

An ultrapure sinusoidal oscillator and high-gain amplifier (both from Krohn-Hite,
Brockton, MA) generated the waveform, which was delivered to the benders by a relay
box under computer control. Allstimuliweresynchronizedtothescannervia a
transistor-transistor logic pulse sent every TR by the MR scanner to a PC running /
Presentationsoftware(Neurobehavioraisystems_fAlbanyzcA)-LargepiezoeIectric
benders (6.6 cm long and 3.3 cm wide) were used to stimulate a large territory of
mechanoreceptors to produce a maximal BOLD functional magnetic resonance imaging
(fMRI) response to the Vibrotactile stimuli. Because fMRI measures neural activity
integrated over time, we attempted to maximize the evoked BOLD response by
delivering stimuli throughout each 2 s trial. Because both central and peripheral
adaptation is observed to Vibrotactile stimulation (Leung, et al. 2005; Tommerdahl, et al.
2005), a pulsed design was used (four repetitions of 250 ms ON/250 ms OFF). The
driving voltage delivered to the benders was 50 V, producing a displacement of 0.5 mm.
Before each experiment, the amplitude of each element was individually adjusted using
the relay box potentiometers (in the range of 40-50 V, 0.4-0.5 mm) to equate the
perceived intensity across benders. This served as a rough control for differences in
efficacy caused by small differences in the placement, attachment, or manufacture of
individual benders.

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