The name is absent

104

a two-alternative, forced-choice (2AFC) tactile discrimination paradigm. For Experiment
3, we developed a somatosensory stimulation apparatus that used piezoelectric
vibrators to allow for precise control of Vibrotactile stimulation frequency and to extend
our results from the previous two experiments to other types of somatosensory stimuli.

Methods

After informed consent, nineteen undergraduate students (9 males; 10 females;
mean age =19.9 years) from Rice University participated in this experiment in exchange
for course credit. All subjects reported having no auditory or somatosensory deficits.

Somatosensory stimuli were delivered using a piezoelectric bending element
(bender). The element was affixed to the dorsal surface of the left hand in each subject
using a cloth bandage wrap. A100 or 200 Hz sinusoidal voltage was applied to the
bender, causing it to oscillate at one of these two frequencies. The duration of the
oscillation was 250 ms, producing the percept of a brief "buzz" Similarto that of a cell
phone in vibrate mode. Because of the low intensity of the tactile stimulus and the
further attenuation of any sounds from the bandage wrap, the piezoelectric bender did
not produce audible vibrations (undetectable increase in sound pressure level as
measured with a SPL meter).

For each subject, the amplitude of the applied voltage to the bender was
adjusted to near-threshold levels and the perceived intensities of the two stimulation
frequencies were equated. The voltage for the 100 Hz vibration was first adjusted to
produce a moderately intense percept. Then, the 200 Hz and the 100 Hz vibrations were

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