Observation of multichannel activity or stimulation with probes in the periphery is particularly challenging. First, simple penetration of a nerve track is much more difficult than brain tissue. We have solved this problem by fabricating probes with very sharp tips formed using shallow boron diffusion. These probes have been shown to penetrate much more readily than those with standard deep diffused tips. """"""""Sieve"""""""" electrodes can also be used when to record from regenerated nerve fibers (Highstein and Bradley). This type of probe has holes through which the fibers can regenerate, and recording sites which surround the holes. The second challenge involves motion with respect to surrounding fixation points is larger then in the cortex or brainstem. The device must somehow be fixed within the nerve track and a cable or transmission system which allows large motions relative to the interconnect area must be provided. We have included barbs and suture loops/holes on several of the custom designs to enhance positional stability. Cables on these designs have been slotted to increase flexibility. Third, in many peripheral situations signals must be transmitted a relatively long distance to reach (or be sent from) the external world. We continue to work with PI Medical in Portland, Oregon to develop a combined system for Dr. Highstein (see collaborative project on Post-processing and Packaging).
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