REALRET · Real-time mammalian retina models
FP6 — Marie Curie Actions (Human Resources and Mobility)
- Duration
- 2005-11-01 → 2007-10-31
- EU contribution
- €183,454
- Participants
- 1
- Scheme
- EIF
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Results in brief
Final Activity Report Summary - REALRET (Real-time mammalian retina models)
The recent advent of genetically encoded optical neuromodulators creates the opportunity for circuit-specific intervention in neurological diseases. One of the diseases most amenable to this approach is retinal degeneration (rd), where the progressive loss of photoreceptors leads to complete and irreversible blindness. We developed a method to specifically activate the ON pathway at the level of the second-order neurons, the bipolar cells. We genetically target a light-activated cation channel, channelrhodopsin-2 (ChR2), selectively to ON bipolar cells of degenerated retinas in vivo. Reporter gene function in retinal neurons was assessed using behavioural experiments, cortical recordings of visual-evoked potentials and extracellular spike recordings with multi-electrode array. We show that in the absence of classical photoreceptors, photosensitive ON bipolar cells induce light-evoked spiking activity in ganglion cells. The rescue of light sensitivity is selective - only circuits that signal light increments are functional, an increase in illumination only stimulates ON ganglion cells. Similar to healthy retinas, parallel processing in the time domain and modification of the information flow by inhibitory circuitry is demonstrated. Sustained and transient ganglion cells are activated in parallel. Although the intensity required stimulating ChR2 is several orders of magnitude greater than that required to stimulate endogenous photo-pigments, many of the response properties are conserved. The surprising functional preservation of the inner retinal synapses in our study suggests that targeting optical neuromodulators to second-order retinal neurons might be a feasible strategy to restore retinal function.
Data: CORDIS, © European Union
Project objective
It has become a standard medical procedure to replace lost body functions with prostheses. Recently some form of visual sensation has been restored in blind patients with the help of retinal implants. Retinal implants use electronics to stimulate retinal g anglion cells based on information recorded with a video camera.It has been known for 50 years that neural circuits in the retina significantly change the space-time properties of the image flow that falls on the photoreceptor cells. Therefore it is desirable to use retinal neural algorithms between the image captured by the video camera and the electronics that stimulate retinal cells.An earlier multi-layer retinal model is far slower than real-time. Based on my experience with retinal modeling in my Ph D thesis lab as well as at the University of California Berkeley and Harvard University my goal is to develop novel spatio-temporal algorithms corresponding to different retinal channels that can be implemented real time.These algorithms are based on state-of-the-art recordings from mammalian retinas. The algorithms use the analog-and-logic cellular wave-computing paradigm called Cellular Nonlinear Networks that was co-invented by my former PhD supervisor.The collaboration with Seville, Spain and two Berkeley, CA laboratories led to existing silicon chips. These chips are integrated into an industrial high-speed camera computer, called Bi-I that was awarded the title `Product of the year at Vision 2003 in Stuttgart.During my postdoctoral training I plan to learn neurobiological methodologies to complement my current engineering knowledge including patch clamping, imaging and confocal microscopy. The host neurobiology laboratory is uncovering the retinal circuit details: Friedrich Miescher Institute, Basel.The project is truly interdisciplinary by its nature; it combines my advanced computer science and engineering background with the host laboratory expertise and facilities in neurobiology.
Original text from CORDIS.
Participants
- NOVARTIS FORSCHUNGSSTIFTUNG, ZWEIGNIEDERLASSUNG FRIEDRICH MIESCHER INSTITUTE FOR BIOMEDICAL RESEARCH · BASELCoordinatorCity levelSwitzerland
Links
Data: CORDIS, © European Union