Current Projects

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.

Isolated Retina Calcium Imaging

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

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

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.

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.

Weiland JD, Anderson DJ. Chronic neural stimulation with Thin-Film, Iridium Oxide Electrodes. IEEE Trans Biomed Eng. 2000 Jul;47(7):911-18.

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.

Whalen III JJ, Weiland JD, Searson PC. Electrochemical Deposition of Platinum from Aqueous Ammonium Hexachloroplatinate Solution. J Electrochem Soc. 2005 152(11):C738-C743.

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

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.

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

Aminat Adebiyi, Nii Mante, Carey Zhang, Furkan E. Sahin, Gerard G. Medioni, Armand R. Tanguay Jr., and James D. Weiland. Evaluation of Feedback Mechanisms for Wearable Visual Aids. Proceedings of the MAP4VIP Workshop, San Jose, CA, July 2013

Adebiyi, Aminat, Paige Sorrentino, Shadi Bohlool, Carey Zhang, Mort Arditti, Gregory Goodrich, and James D. Weiland. “Assessment of feedback modalities for wearable visual aids in blind mobility.” PloS one 12, no. 2 (2017): e0170531.