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separated touches were delivered to the left or right hand or foot of the subject. In the
second experiment, closely spaced touches were delivered to three fingers on the right
hand and to the right foot. Our analyses focused on three regions of the somatosensory
network: primary somatosensory cortex {S1), secondary somatosensory cortex {S2), and
a region of lateral occipital-temporal cortex, MST∕STP, that has traditionally been
labeled as visual association cortex but also responds to touch (Beauchamp, et al. 2008;
Beauchamp, et al. 2007; Blake, et al. 2004; Hagen, et al. 2002; Ricciardi, et al. 2007).

Most MVPA studies have used blocked designs, in which stimuli from the same
category are grouped. Block designs are problematic in the somatosensory system,
where adaptation is pronounced both peripherally and centrally (Leung, et al. 2005;
Tommerdahl, et al. 2005). Rapid event-related designs are an efficient way to present
many different stimuli while minimizing adaptation. We developed a simple technique
to analyze single trials of somatosensory stimulation presented in a rapid event-related
design using support vector machines (SVMs), a supervised learning method that
performs efficiently at high-dimensional classification tasks like those found in fMRI (Cox
and Savoy 2003; LaConte, et al. 2005).

Methods

Subjects were recruited and informed consent was obtained in accordance with
the University of Texas Committee for the Protection of Human Subjects. Subjects were
scanned using a 3 tesla whole-body MR scanner (Phillips Medical Systems, Bothell, WA).

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