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Neuroscience
Cluster Scientific Retreat |
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Postdoctoral Scholar, Department of Organismal Biology & anatomy Current brain-machine interfaces (BMI) largely rely
on visual feedback to guide cursor or robot movements. It is well known,
however, that patients suffering from the loss of proprioceptive sense
exhibit considerable motor deficits such as slow and uncoordinated
movements. We designed an experiment to test the hypothesis that the
addition of naturalistic proprioceptive feedback would improve the movement
of a cortically-driven cursor. Two monkeys (Macaca mulatta) used a BMI[i]
to move a visual cursor and hit a sequence of randomly placed targets while
resting their arm in a two-link robotic exoskeleton. The experiment
consisted of three different conditions. A micro-electrode array
composed of 100 electrodes was used to record the spiking activity of an
ensemble of neurons in primary motor cortex (MI) neurons under three
different conditions. In the first condition, Visual Feedback Decoding,
the monkeys moved the cursor via the BMI voluntarily maintained a static arm
posture in the robotic exoskeleton and thus did not receive veridical
proprioceptive feedback regarding the cursor location. Next, in the
Visual and Proprioceptive Feedback Decoding condition, the monkeys controlled
the cursor via the BMI while their arm was driven by the exoskeleton through
the visual cursor trajectories, thereby providing the monkeys a veridical
proprioceptive estimate of the cursor position. Lastly, we included a
control condition, Visual and Noisy Proprioceptive Feedback Decoding, in
which the monkeys moved the cursor via the BMI while their arm was moved
through a trajectory uncorrelated to the decoded trajectory of the visual
cursor. We demonstrate for the first time that
proprioceptive feedback can be used together with vision to significantly
improve control of a cursor driven by neural activity in the primary motor
cortex. When the visual and proprioceptive feedback was congruent, the time
to successfully complete the task decreased, and the cursor paths became
straighter when compared with the incongruent feedback conditions.
These findings suggest that BMI control can be significantly improved in
paralyzed patients with residual proprioceptive sense and provide the
groundwork for augmenting cortically-controlled BMIs with multiple forms of
natural or surrogate sensory feedback. 09/16/2009 |