Figure 2.

A, Phase-encoded stimulation procedure. The tip of the index finger (red, d2), middle finger (green, d3), ring finger (blue, d4), and little finger (yellow, d5) was stimulated in succession, in repeated cycles (12 cycles per run). To reduce scanning time, the homologous fingers of the right and left hands were stimulated simultaneously. B, Illustrative phase-encoded response to periodic fingertip stimulation. The figure shows the raw BOLD response in four voxels of interest (thin lines; data were motion-corrected and the linear trend removed). The locations of the voxels are marked with a star on the cortical surface of the left primary somatosensory cortex of 1 participant. Thicker lines indicate the average of the raw BOLD response across 12 cycles of stimulation. The vertical, dashed, white line is displayed to facilitate the visualization of the shift of the phase of the BOLD response across the four voxels. The F statistics of the signal at different phases are rendered on the inflated cortical surface and color-coded as in A (cluster-corrected p < 0.01). Phases corresponding to rest have been truncated.