79
for foot vs. hand stimulation. The ability of both ROIs to perform two-way classification
(left vs. right) was tested (Fig. 3B,C). Slhand was better at predicting side of hand
stimulation than side of foot stimulation (75% vs. 54%, p < 0.001). Slfootwas
significantly better at predicting side of foot stimulation than side of hand stimulation
A. Performance for four-way classification (right hand, left hand, right foot, left foot). The mean
performance of the classifier when classifying single trials in a scan series not used for training,
averaged across 8 subjects (error bars shows the SEM). The gray bar shows the performance when
the classifier was trained and tested on voxels in all ROIs; colored bars show performance when
classifier was trained and tested only on voxels in a single ROI (SI, S2, MST∕STP). Chance
performance was 25% (dashed line).
B. Accuracy of two-way classification (left hand vs. right) in three ROIs.
C. Accuracy of two-way classification (Ieftfootvs. right foot) in three ROIs.
D. Accuracy of three-way classification in experiment 2 (thumb vs. middle finger vs. pinky finger).
InapreviousstudyjMsTsignificantlypreferredhandstimuIationtofoot
stimulation, perhaps because of a role in eye-hand coordination (Beauchamp, et al.
2007). We hypothesized that the relatively poor MST∕STP performance in 4-way
classification might reflect differential performance on hand and foot classification.
Therefore, the ability of MST∕STP to classify hand stimuli (left vs. right) and foot stimuli
(left vs. right) was also separately tested. MST∕STP classification performance was