Surgery – Diagnostic testing – Structure of body-contacting electrode or electrode inserted...
Reexamination Certificate
2001-11-16
2004-12-07
Cohen, Lee S. (Department: 3739)
Surgery
Diagnostic testing
Structure of body-contacting electrode or electrode inserted...
C607S116000, C029S825000
Reexamination Certificate
active
06829498
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates, generally, to a device for creating a neural interface with the central nervous system and a method for making the same. More particularly, the present invention is directed to a device for creating a multi-channel neural interface for long-term recording or stimulation in the cerebral cortex.
BACKGROUND OF THE INVENTION
Since the advent of the simple intracortical single microelectrode four decades ago, continued technical advances in the biological, materials and electronics fields have fueled a steady advance in the development of neural interfaces. Today, advanced devices that are available for implantation into the brain have multiple electrode sites, are chronically implantable, and can include circuitry for on-board signal processing. These complex structures are ideal for many potential clinical applications and basic research applications. For example, there is continuing evidence that a neural interface providing reliable and stable long-term implant function could be used for the realization of clinically useful cortical prostheses for the blind. In addition, the utility of multi-electrode arrays has already been demonstrated in basic research studies which have provided fundamental insights into parallel processing strategies during sensory coding in the brain. However, the complex neural interfaces available today have not yet demonstrated the necessary longevity required to support greater strides in the basic neurophysiological research or clinical neuroprosthetic fields. These gains will only be possible when electrode systems can be made to function reliably and consistently for the lifetime of the implanted subject.
Development of the first single penetrating electrode device spawned the first of three generations of intracortical neural interfaces. In the first generation, microelectrodes consisted of known electrically conductive materials that were stiff enough to be inserted through either the pia or the dura membrane without buckling. These microelectrodes are still in use today and may consist of simple materials such as a stiff and sharpened insulated metallic wire or a drawn glass pipette filled with an aqueous conductor. Because of their high impedance and small site sizes, these electrodes must be rigorously positioned near their target neurons using precision micromanipulation in order to be effective. Recordings can only be held for several minutes to several hours with these microelectrodes before repositioning is required which reduces their attractiveness for long term chronic implant.
The first generation devices have been upgraded and researchers now routinely employ multiple single microelectrodes aligned into arrays to provide ever-increasing numbers of electrode sites in one device. Some devices have positional electrodes while others have modified single electrodes (with larger site sizes and/or reduced impedances) which are capable of recording neural activity without precise positioning. These devices can remain functional upon implant for one to twelve months but the same individual neurons can not be ‘tracked’ for longer than about six weeks.
The second generation of implantable neural interfaces includes complex electrode designs which allow for batch fabrication of multiple-site devices. These devices are usually monolithic, multi-site devices having the capability for integrated electronics and cabling, and are created by incorporating planar photolithographic and/or silicon micromachining manufacturing techniques from the electronics industry. Devices made of silicon, or devices incorporating molybdenum, that are stiff enough to penetrate the pia upon implantation have been used for recording or stimulation of the cerebral cortex. Like first generation devices, these intracortical interfaces can remain secure in the brain for extended periods of time but recording quality and electrode yield typically diminish with time. Other devices are polyimide-based and have been designed to provide a conformal coverage when placed upon the curved surface of the brain but many of these applications require electrodes to be implanted into the cortex.
A third generation of implantable neural interfaces has developed in the last decade. These latest intracortical electrodes incorporate ‘bioactive’ components and use standard electrically conductive materials in combination with biologically active species in an effort to improve the performance and function of the neural interface. For example, by ‘seeding’ a non-traditional glass microelectrode with the active biospecies nerve growth factor (NGF), Kennedy et al. have succeeded in creating a neural interface which actively promotes neurite growth towards the recording site.
J Neurosci. Methods
, vol. 29, no. 3, pp. 181-193 (September 1989). These so-called ‘cone electrodes’ are only single channel devices but their efficacy is remarkable. The signal to noise ratio of the recorded signals are five to ten times those found in second generation devices and the signals remain stable over extended implant durations. Nevertheless, these third generation devices, like the first and second generation devices, have failed to function reliably and consistently for the lifetime of a subject having the device implanted.
The promise of advanced neuroprosthetic systems to significantly improve the quality of life for a segment of the deaf, blind, or paralyzed population hinges on the development of an efficacious and safe neural interface for the central nervous system. Accordingly, there is a need for a reliable, consistent, and long-term neural interface device for the central nervous system which overcomes the shortcomings of the first, second and third generation devices described above.
SUMMARY OF THE INVENTION
Briefly, the present invention is directed to a thin-film polyimide-based, multi-channel intracortical interface for the central nervous system which is manufactured with standard planar photo-lithographic complementary field-effect transistor (CMOS)-compatible techniques. Electrode sites of the present invention device are preferably gold pads with gold traces (leading to a connector) sandwiched in a mechanically ‘flexible’ and electrically insulating polyimide substrate. The flexibility of the polyimide is intended to provide a strain relief against the forces of ‘micromotion’ between the tissue and the implanted device and also allows for the device to be manipulated into a three-dimensional structure. In addition, the polyimide surface chemistry is amenable to modifications and preparations which allow a host of bioactive organic species to be either adsorbed or covalently bonded to its surface. Device flexibility and bioactivity are intended to provide an optimal implant environment and extend the longevity of the tissue-electrode interface. The device structure may also have an integrated polyimide cable which provides for efficient contact points for a high-density connector.
In accordance with one embodiment of the present invention, an implant device for creating a neural interface with the central nervous system includes at least one electrode sandwiched within a bi-layer polyimide insulating substrate and at least one via formed within the bi-layer polyimide substrate. In accordance with a further aspect of the present invention, the electrode and via are located on a shaft of the device and the device can then be connected to a connector by way of an integrated polyimide cable and feedthrough interconnect system. The device preferably includes more than one shaft with each shaft having at least one electrode thereby forming an array of electrodes. Each shaft may also include more than one via in which a bioactive species is placed to help create the ideal device-tissue interface. Separate vias may contain different and distinct bioactive species.
In accordance with another aspect of the invention, the shafts may be bent to form a three dimensional device wherein only the shafts would be implanted into the corticle mantle. This cap
Kipke Daryl
Pellinen David S.
Pivin David
Rousche Patrick
Williams Justin
Arizona Board of Regents
Cohen Lee S.
Snell & Wilmer L.L.P.
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