Visual System Response to Electrical Simulation
The long-term goal of this project is investigate safe and effective retinal stimulation paradigms. We conduct experiments in animal models, including models of inherited outer retinal degeneration, and in humans with Argus II retinal implants. In animals, we use single cell electrophysiology and calcium imaging to assess the response at cellular resolution. We also use optical coherence tomography to measure the safety of high-intensity, continuous stimulation. To assess visual receptive fields, we measure visual cortex responses in small animals. Human testing focuses on the shape and other perceptual characteristics of single and multi-channel stimulation.
Chang Y-C, Haji-Ghaffari D, Chow RH, Weiland JD . Stimulation strategies for selective activation of retinal ganglion cell soma and threshold reduction. 2019 J. Neural Eng. 16 026017
Walston ST, Chow RH, Weiland JD. Direct measurement of bipolar cell responses to electrical stimulation in wholemount mouse retina. Journal of neural engineering 15, no. 4 (2018): 046003.
Weitz AC, Nanduri D, Behrend MR, Gonzalez-Calle A, Greenberg RJ, Humayun MS, Chow RH, Weiland JD. Improving the spatial resolution of epiretinal implants by increasing stimulus pulse duration.Science Translational Medicine, 16 Dec 2015: Vol. 7, Issue 318, pp. 318ra203. DOI: 10.1126/scitranslmed.aac4877
Behrend MR, Ahuja A, Humayun MS, Chow R, Weiland JD. Resolution of the Epiretinal Prosthesis is not Limited by Electrode Size. IEEE Trans Neural Syst Rehabil Eng. 2011 Aug;19(4):436-42. Epub 2011 Apr 19.
Ahuja AK, Behrend MR, Kuroda M, Humayun MS, Weiland JD. An In Vitro Model of a Retinal Prosthesis. IEEE Trans Biomed Eng. 2008 June 55(6):1744-53.
Chan L, Lee EJ, Humayun MS, Weiland JD. Both Electrical Stimulation Thresholds and SMI-32 Immunoreactive Retinal Ganglion Cell Density Correlate with age in S334ter line 3 Rat Retina. Journal of Neurophysiology AJP – JN Physiol June 2011 vol. 105 no. 6 2687-2697
Yanai, D., Weiland, J.D., Mahadevappa, M., Greenberg, R.J., Fine, I. & Humayun, M.S. (2007). Visual performance using a retinal prosthesis in three subjects with retinitis pigmentosa. American Journal of Ophthalmology, 143, 820-827.
de Balthasar C, Patel S, Roy A, Freda R, Greenwald S, Horsager A, Mahadevappa M, Yanai D, Mcmahon MJ, Humayun MS, Greenberg RJ, Weiland JD, Fine I. Factors affecting perceptual thresholds in epiretinal prostheses. Invest Ophthalmol Vis Sci. 2008 Jun; 49(6):2303-14.
Nanduri D, Horasager A, Boynton G, Humayun MS, Greenberg RJ, Weiland JD. Frequency and Amplitude Modulation Have Different Effects on the Percepts Elicited by Retinal Stimulation. Invest. Ophthalmol. Vis. Sci. January 20, 2012 vol. 53 no. 1 205-214
Brain Imaging in Humans with Retinal Implants
The long-term goal of this project is to study how the human brain responds to sight recovery. Prior work has shown that even in the adult brain, whereas structural plasticity is limited, functional plasticity results in profound changes in how the brain processes sensory input. The visual cortex of people who lost vision in adulthood can become active in response to tactile input, a phenomenon known as cross-modal plasticity. What is unclear is the impact of this functional plasticity on sight recovery therapy such as retinal prostheses. Prior work in our lab (1) has established the feasibility of brain imaging in Argus II retinal prosthesis patients and (2) studied cross-modal activation in patients with retinitis pigmentosa.
Crossmodal plasticity in Blindness. The blue arrows point to V1, which is a activated (as measured by fMRI) during a tactile task. We are investigating whether or not usage of the Argus II retinal implant can reverse this functional reorganization of the brain.
Cunningham SI, Weiland JD, Bao P, Lopez-Jaime GR, Tjan BS. Correlation of vision loss with tactile-evoked V1 responses in retinitis pigmentosa. Vision research, 2015, 111, 197-207.
Cunningham SI, Shi Y, Weiland JD, Falabella P, Olmos de Koo LC, Zacks DN, Tjan BS. Feasibility of Structural and Functional MRI Acquisition in Argus® II Retinal Prosthesis Patients: A Case Study with Unpowered Implants. Translational Vision Science and Technology 4(6), 2015.
Weiland JD, Faraji B, Greenberg RJ, Humayun MS, Shellock F. Assessment of MRI issues for the Argus II retinal prosthesis. Magn Reson Imaging, 2012 Apr;30(3):382-9
Materials for Bioelectronic Implants
We evaluate and create new materials and processes for bioelectronic implants. Electrode materials are critical to making implants safe and efficient. We have created a novel Platinum-Iridium alloy that has high surface area and mechanical robustness. In vivo tests with this material show excellent electrical and neural recording properties. We have also investigated multi-layer, multi-material conformal films for coating electronics prior to implantation.
Uncoated electrode (left) and the same electrode (right) after electrodeposition of Platinum-Iridium nanofractal film. This material has excellent charge transfer properties (Disclosure – Dr. Weiland has a financial interest in Platinum Group Coatings, which is commercializing this material).
Lee CD, Hudak EM, Whalen JJ, Petrossians A, Weiland JD. Low-Impedance, high surface area pt-ir electrodeposited on cochlear implant electrodes. Journal of The Electrochemical Society 165, no. 12 (2018): G3015-G3017.
Petrossians A, Whalen III JJ, Weiland JD, Mansfeld F. Electrodeposition and Characterization of Thin-Film Platinum-Iridium Alloys for Biological Interfaces. Journal of the Electrochemical Society, Journal of the Electrochemical Society, Vol.158, No.6, S15-S15, 2011
Whalen III JJ, Weiland JD, Searson PC. Electrochemical Deposition of Platinum from Aqueous Ammonium Hexachloroplatinate Solution. J Electrochem Soc. 2005 152(11):C738-C743.
Weiland JD, Anderson DJ, Humayun MS. In Vitro Electrical Properties for Iridium Oxide vs. Titanium Nitride Stimulating Electrodes. IEEE Trans Biomed Eng. 2002 Dec;49(12 Pt 2):1574-9.
Weiland JD, Anderson DJ. Chronic neural stimulation with Thin-Film, Iridium Oxide Electrodes. IEEE Trans Biomed Eng. 2000 Jul;47(7):911-18.
Wearable Computer Vision Systems for Blind Navigation
Our team is assessing the ability of computer vision programs to interpret a scene in real-time and use this information to guide a blind person as the search for an object and/or navigate through a neighborhood. We demonstrated that blind people can use simple verbal or vibrotactile cues to direct them to complete reach and grasp as well as navigation tasks.
A video of a blind test subject using our crosswalk navigation system is below. The subject is wearing a head-mounted camera with processing capability and audio output. This prototype system can detect the location and state of a crosswalk sign and guide the user across. In the video below, frames from the headworn camera are shown with superimposed localization parameters and guiding cues (such as “forward” or “veer right” ). Research team member flank the user for safety (not shown in frames). Towards the end of the clip, the subject drifts left and is instructed to “veer right”.
Mante NQ, Weiland JD. Visually impaired users can locate and grasp objects under the guidance of computer vision and non-visual feedback. In 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), pp. 1-4. IEEE, 2018.
Adebiyi A, Sorrentino P, Bohlool S, Zhang C, Arditti M, Goodrich G, Weiland JD. Assessment of feedback modalities for wearable visual aids in blind mobility. PloS one 12, no. 2 (2017): e0170531.
Adebiyi A, Mante NQ, Zhang C, Sahin FE, Medioni GG, Tanguay Jr. AR, Weiland JD. Evaluation of Feedback Mechanisms for Wearable Visual Aids. Proceedings of the MAP4VIP Workshop, San Jose, CA, July 2013
Parikh N, Itti L, Weiland JD. Saliency-based image processing for retinal prostheses. J Neural Eng. 2010 Feb;7(1):16006. Epub 2010 Jan 14.PMID: 20075505
Parikh N, Itti L, Humayun MS and Weiland JD. Performance of visually guided tasks using simulated prosthetic vision and saliency-based cues 2013. J. Neural Eng. 10 026017 doi:10.1088/1741-2560/10/2/026017
Pradeep V, Medioni G, Weiland JD. A Wearable System for the Visually Impaired. International IEEE Engineering in Medicine and Biology (EMBS) Conference 2010