Patrick J. Nasiatka

Restoring lost cognitive function

A prosthetic device that functions in a biomimetic manner to replace information transmission between cortical brain regions is considered. In such a prosthesis, damaged CNS neurons is replaced with a biomimetic system comprised of silicon neurons. The replacement silicon neurons would have functional properties specific to those of the damaged neurons and would both receive as inputs and send as outputs electrical activity to regions of the brain with which the damaged region previously communicated. Thus, the class of prosthesis proposed is one that would replace the computational function of the damaged brain and restore the transmission of that computational result to other regions of the nervous system.

Attention biased speeded up robust featureS (AB-SURF): A neurally-inspired object recognition algorithm for a wearable aid for the visually-impaired

Humans recognize objects effortlessly, in spite of changes in scale, position, and illumination. Emulating human recognition in machines remains a challenge. This paper describes computer vision algorithms aimed at helping visually-impaired people locate and recognize objects. Our neurally-inspired computer vision algorithm, called Attention Biased Speeded Up Robust Features (AB-SURF), harnesses features that characterize human visual attention to make the recognition task more tractable. An attention biasing algorithm selects the most task-driven salient regions in an image. Next, the SURF object recognition algorithm is applied on this narrowed subsection of the original image. Testing on images containing 5 different objects exhibits accuracies ranging from 80% to 100%. Furthermore, testing on images containing 10 objects yields accuracies between 63% and 96% for the 5 objects that occupy the largest area within the image subwindows chosen by attention biasing. A five-fold speed-up is attained using AB-SURF as compared to the time estimated for sliding window recognition on the same images.

High density electrical interconnections in liquid crystal polymer (LCP) substrates for retinal and neural prosthesis applications

Retinal prostheses implemented by means of electrical stimulation of retinal ganglion cells have been previously demonstrated with 16 and 60 channel microstimulator arrays. Blind patients with severe retinal degeneration (e.g., retinitis pigmentosa (RP) have been able to use these devices to navigate and read large letters. However, to dramatically improve the effectiveness of such prostheses, and to enable a variety of neural stimulation implants, channel densities of 1000 per cm2 and higher are highly desirable. This paper reports on a novel approach to an integrated bioelectronic package with high density electrical feedthroughs, capable of 1024 stimulator channels in a 5 mm × 5 mm area using liquid crystal polymer (LCP) substrates to enable implantable retinal prostheses. A novel fusion bonding process was demonstrated to achieve fine pitch interconnections with high adhesion strength and biocompatible metal-polymer interfaces. Helium leak rates of 1 × 10−9 mbar-1/sec were measured for LCP samples without feedthroughs, representative of penetration through the bulk LCP film, and leak rates of < 5 × 10−8 mbar-1/sec were measured for feedthrough array samples, comparable to leak rates demonstrated for glass substrates with metallized vias.

Chip-scale packaging for bioelectronic implants

Next generation miniaturized bioelectronic implants will require improved hermetic packaging technology to achieve the system requirements for treating complex neurological conditions. We describe herein three key advances towards enabling chip-scale packaging for bioelectronic implants. First, we demonstrate multilayer, multi-material films that have improved barrier properties to contaminating ions and can be deposited conformally on three-dimensional structures. Second, we characterize integrated sensors capable of detecting contaminants, to serve both as tests of deposited coating hermeticity and as an early warning system to predict implant failure. Third, a high-density hermetic feedthrough is described that will enable long-term deployment of state-of-the-art neural interface arrays. Collectively, this work represents a significant advance in packaging technologies for medical implants.

Intraocular camera for retinal prostheses: Design constraints based on visual psychophysics

Optical system design constraints for an intraocular camera are determined by visual psychophysics techniques, including pixellation limits adequate for navigation and object identification, optimal pre- and post-pixellation blurring, and the elimination of gridding artifacts.