Haptics For Neuroprosthetics

Skin-Stretch Feedback for Brain-Computer Interfaces

Haptic feedback can provide brain-computer interface (BCI) users with additional information about their brain activity without taxing the auditory and visual systems on which they heavily rely. To date, however, only vibrotactile feedback - vibrations applied to the skin - and kinesthetic feedback - forces applied to the limbs - have been proposed for BCIs. Although each has advantages, neither form of feedback is ideal for a neurally connected assistive device. The ideal haptic feedback for BCIs should combine the best of vibrotactile and kinesthetic feedback, communicating natural trajectory information - for example, the motion of a computer cursor - in a safe and portable package. By encoding amplitude and direction without the need for large actuators, skin stretch, or cutaneous shear force, is well suited for the task.

You can see a top-down schematic of our skin-stretch device in the figure above. Its five-bar linkage allows for shear force in two (planar) degrees of freedom. The shear force is translated to skin stretch by a frictional tactor at the end of the linkage. Taking advantage of the high density of mechanoreceptors (biological sensors that detect tactile stimuli) in the fingers, the tactor is designed to stay in contact with the user's index fingertip. The nature of the skin stretch provided by the tactor is directly controlled by the user's neural activity, which is monitored by an EEG-based neuroheadset. To assess the impact of this haptic feedback on the user's ability to control his or her neural activity, we have designed a one-dimensional cursor-movement task using the headset. We are currently recruiting "expert" BCI users for a study with the task.



  • Stanford University
  • National Science Foundation GRFP

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