Preparation of a neural electrode implantation device for in-vivo surgical use.

An instrument designed for the implantation of neural electrode array devices has been refined in preparation for use in cortical implantation procedures in non-human primates. This instrument has undergone extensive testing to ensure its successful first use in a live surgical setting. This work describes the modifications made to the instrument and the testing performed on it during that preparatory period as well as planned future modifications and augmentations.

Chronic in-vivo testing of a 16-channel implantable wireless neural stimulator.

Here, we report on chronic in-vivo testing of a 16-channel wireless floating microelectrode array (WFMA) in a rat sciatic nerve model. Muscle threshold currents, charge injection levels, and charge density were monitored for electrodes of two WFMA devices implanted into animal subjects over a five month period. This type of wireless stimulation device could eliminate problems associated with percutaneous connectors for a variety of neural prostheses and other medical devices.

Chronic and low charge injection wireless intraneural stimulation in vivo.

Functional stability and in-vivo reliability are significant factors determining the longevity of a neural interface. In this ongoing study, we test the performance of a wireless floating microelectrode array (WFMA) over a period of 143 days. The topography of the microelectrodes has allowed for selective stimulation of different fascicles of the rat sciatic nerve. We confirmed that motor evoked thresholds remain stable over time and that the nerve stimulation charges were within tissue safety limits. Importantly, motor evoked responses were elicited at threshold currents in fully awake animals without causing pain or discomfort. These data validate the use of the WFMA system for intraneural interfacing of peripheral nerves for neuroprosthetic and bioelectronics medical applications.

Device for the implantation of neural electrode arrays.

Electrode arrays used in neural recording and stimulation applications must be implanted carefully to minimize damage to the underlying tissue. A device has been designed to improve a surgeon's control over implantation parameters including depth, insertion velocity, and insertion force. The device has been designed to operate without contacting tissue and to respond to tissue movements in real time during insertion. This device uses an electrical motor to drive electrode arrays into tissue and allows for the monitoring of and response to electrode depth during insertion. A prototype device has been constructed and tests have been performed to determine the velocity and force characteristics of the motor when inside the device housing. Future versions of the device will use a custom-designed motor with longer linear travel, which will allow the insertion device to be held farther from tissue while still ensuring proper array insertion.

Identification and quantification of electrical leakage pathways in floating microelectrode arrays.

The long-term reliability of neural recording and stimulation electrode arrays is becoming the limiting factor for neural interfaces. For effective electrode design, electrical connection to the surrounding neural tissue and fluid should be limited to the electrode tips, with all other leakage currents minimized. It is the goal of this study to identify and quantify electrical leakage within commercially available floating microelectrode arrays (FMAs). Both short term and accelerated stress tests were performed on entire FMAs, as well as on individual electrodes typical of such arrays. Preliminary results of these tests indicate that leakage currents are present due to water penetration of their insulation layer initially, but that prolonged water exposure at high temperature may seal the defects that cause these currents. SEM photos taken of the electrode shafts show extensive defect regions that may correlate with the test data.