Novel MRI-compatible tactile stimulator for cortical mapping of foot sole pressure stimuli with fMRI.

Foot sole somatosensory feedback is critical to motor control and declines with aging and disease. To enable study of cortical networks underlying foot sole somatosensation, we developed a pneumatic tactile stimulator capable of producing one degree-of-freedom (DOF) oscillations with preset waveform, frequency (≤10 Hz), force magnitude (5-500 N), duty cycle (20-100%), and contacted surface area over which pressures are applied to the foot sole. Image tests (anatomical/functional/field map) of a phantom demonstrated that the device is compatible with 3 T MRI. Gradient-recalled echo-planar images of seven healthy young adults using a typical block-designed 1 Hz sinusoidal stimulation protocol revealed significant activation contralaterally within the primary somatosensory cortex and paracentral gyrus, and bilaterally within the secondary somatosensory cortex. The stimulation system may therefore serve as a research tool to study functional brain networks involved in the perception and modulation of foot sole somatosensation and its relationship to motor control.