The document summarizes retinal anatomy and modeling. It discusses the layers of the retina including photoreceptors, bipolar cells, horizontal cells, amacrine cells, and ganglion cells. It describes the connections between these cells, including chemical synapses and electrical gap junctions. The goal of the author's PhD is to improve an existing retinal model to produce synchronized spike outputs from ganglion cells by adding connections between ganglion cells and between ganglion and amacrine cells.
Anatomy of the Eye: Human Eye Anatomy | Aakash Eye HospitalAakash Eye Hospital
Aakash Eye Hospital - Descriptions and pictures of Anatomy of the Eye, Human Eye Anatomy, Parts of the Eye Explained, physiology nad how the eye and vision work information.
Anatomy of the Eye: Human Eye Anatomy | Aakash Eye HospitalAakash Eye Hospital
Aakash Eye Hospital - Descriptions and pictures of Anatomy of the Eye, Human Eye Anatomy, Parts of the Eye Explained, physiology nad how the eye and vision work information.
Aakash Eye Hospital is one of the largest eye hospital in Ahmedabad, Visnagar and Bharuch.
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"Understanding Social Movements with Case Studies about Vegan Animal Advocacy...Roger Yates
The Vegan Information Project presented an Informal lecture/workshop on "Understanding Social Movements with Case Studies about Vegan Animal Advocacy" by Dr. Roger Yates, at The Outhouse, Dublin, 11th November, 2013.
This is part of VIP's World Vegan Month programme of events.
This presentation addresses 9 common barriers to change in the educational field. It will be beneficial to anyone contemplating making a change as it allows you to view the effects of the change from several different viewpoints.
Aakash Eye Hospital is one of the largest eye hospital in Ahmedabad, Visnagar and Bharuch.
our expertise in Cataract Surgery ,Glaucoma, Bladeless Lasik Surgery,
Squint Surgery, Pterygium, eye Treatment and Conjunctivitis Treatment.
"Understanding Social Movements with Case Studies about Vegan Animal Advocacy...Roger Yates
The Vegan Information Project presented an Informal lecture/workshop on "Understanding Social Movements with Case Studies about Vegan Animal Advocacy" by Dr. Roger Yates, at The Outhouse, Dublin, 11th November, 2013.
This is part of VIP's World Vegan Month programme of events.
This presentation addresses 9 common barriers to change in the educational field. It will be beneficial to anyone contemplating making a change as it allows you to view the effects of the change from several different viewpoints.
Many small businesses do not understand why it is that the net profit for a month does not represent the amount of money in the checking account. The question is, "Where is the money if I made that much profit?" This Tom Shay provides insight to the solution. www.profitsplus.org
Leger Marketing, with its Members of WIN, presents the 3rd wave of the WIN Crisis Index.
WIN, a network which brings together the greatest independent firms of Market Research throughout the world, presents the third wave of the WIN Crisis Index. The survey evaluates people’s perception and behaviours due to the Economic Crisis.
Learn how individuals’ economic perceptions, spending behaviours and psychological health have changed because of the Economic Crisis over the year.
Anatomy of the Human Eye ( PDFDrive ).pdfRockyIslam5
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ARTIFICIAL RETINA USING THIN FILM TRANSISTORS DRIVEN BY WIRELESS POWER SUPPLYManiroop Badam
Artificial retinas have been ardently desired to recover the sight sense for sight-handicapped people. We have verified that an artificial retina using poly-Si TFTs can be driven by wireless power supply. It is confirmed that the irradiated light distribution can be reproduced as the output voltage distribution owing to the parameter optimization of the wireless power supply system.
Analysis of large scale spiking networks dynamics with spatio-temporal constr...Hassan Nasser
Recent experimental advances have made it possible to record up to several hundreds of neurons simultaneously in the cortex or in the retina. Analysing such data requires mathematical and numerical methods to describe the spatio-temporal correlations in population activity. This can be done thanks to Maximum Entropy method. Here, a crucial parameter is the product NxR where N is the number of neurons and R the memory depth of correlations (how far in the past does the spike activity affects the current state). Standard statistical mechanics methods are limited to spatial correlation structure with
R = 1 (e.g. Ising model) whereas methods based on transfer matrices, allowing the analysis of spatio-temporal correlations, are limited to NR = 20.
In the first part of the thesis we propose a modified version of the transfer matrix method, based on the parallel version of the Montecarlo algorithm, allowing us to go to NR = 100.
In the second part we present EnaS, a C++ library with a Graphical User Interface developed for neuroscientists. EnaS offers highly interactive tools that allow users to manage data, perform empirical statistics, modeling and visualizing results.
Finally, in a third part, we test our method on synthetic and real data sets. Real data set correspond to retina data provided by neuroscientists partners. Our non extensive analysis shows the advantages of considering spatio-temporal correlations for the analysis of retina spike trains, but it also outlines the limits of Maximum Entropy methods.
For more information about the software that I co-developed with my colleagues, please visit this page:
https://enas.inria.fr/
For more information about the publications, please visit this page:
https://scholar.google.fr/citations?user=L97ZODwAAAAJ
For the thesis, please visit this link:
https://www.theses.fr/178166669
3. Context
• Presentation of two articles:
– T. Gollisch, M. Meister: Eye Smarter than Scientists
Believed: Neural Computations in Circuits of the
Retina (2009).
– Helga Kolb: How the Retina Works (2003).
• Discussion in the scope of my PhD: How to
reproduce the retinal responses.
4. Visual pathways (2 min) Eye (2 min) Retina (5 min)
Discussion
3 min Model (3 min) Interaction between cells (7 min)
5. What is a Visual pathway?
- It’s a set of cells bodies and
nerves conducting impulses from
the eye to the cerebral cortex
- Reception of external images
and transport of visual
information
Retina Optic nerve Visual Cortex
V1, V2…
(ganglion cells)
light
6. Eye
Three different layers:
1- The external layer, formed
by the sclera, pupil and
cornea.
2- The intermediate layer,
divided into two parts:
anterior (iris, lens and ciliary
body) and posterior (choroid).
3- The internal layer, or the
sensory part of the eye, the
retina.
7. Retina
-The retina is approximately 0.5 mm thick and lines the back of the
eye.
- Optic nerve contains: RGC axons + Blood vessels
8. Retina
Absorption of light
Light direction
All vertebrate retinas are composed of three layers of nerve cell bodies
and two layers of synapses. The retina is designed according to the life
style!. EX: Fish, Frog, Turtle have 5 types of cones Colored vision.
9. • Layers of nerve cells:
– Outer nuclear layer
contains cell bodies of
the rods and cones.
– Inner nuclear layer
contains cell bodies of
the bipolar, horizontal
and amacrine cells.
– Ganglion cell layer
contains cell bodies of
ganglion cells and
displaced amacrine cells
• Layers of synapses:
– Outer plexiform layer (OPL)
where connections between
rod and cones
– Inner plexiform layer (IPL),
and it functions as a relay
station for the vertical-
information-carrying nerve
cells, the bipolar cells, to
connect to ganglion cells.
11. Photoreceptors
• 2-3 types of cones
– Cones are concentrated in the fovea centralis.
– 6-7 millions ("red" cones (64%), "green" cones (32%),
and "blue" cones (2%))
– Sensitive to colors.
– Visual acuity.
• 1 types of Rods.
– ~ 120 millions.
– More sensitive (1000 times) than cones but not
sensitive to the colors Night vision.
15. The retina is:
-A photo transducer that transforms
photons to current?
-The retina is a processor to detect
image features (motion, contrast,
edges)?
-The retina is a sophisticated processor
that exceed the last two expectations?
Retina smarter than scientists believed!
More than 50 types of connected cells.
FM Signal
17. (All-or-none principle)
Chemical Synapse
-The action potential arrives in the Pre synaptic cells (Indicator: Increasing of
calcium concentration inside)
-Releasing of neurotransmitters from their vesicles in the synaptic cleft.
-Fixation of neurotransmitters on the receptor of postsynaptic cleft.
-Triggering of the action potential in the post synaptic cell.
In the retina: Only RGC obeys to All-or-none principle. Others shows graded behavior
(the postsynaptic potential is proportional to the presynaptic potential)
18. Electrical connections – Gap junctions
-Allow direct and faster connection between two cells.
-Resistance for current depends on several parameters (Acidity degree,
Calcium concentration, temperature, …).
-Simple model = Resistance. Complicated model: Current transfer
taking into account the majority of parameters to produce biological
plausibility.
19. Let’s see how retina works:
Connections roles in the information
transport and parallel processing.
22. Functional role of Gap Junction
- Gap junctions exists between cells of
every type in the retina.
Stewart A et al. 2009
23. … Between Photoreceptors
• Blurring of visual signal.
• Reduction in acuity.
• Coupling between photoreceptors sums the
correlated visual signal and attenuates the
asynchronous noise which comes from photo-
chemical transduction (improve the SNR by
80%). Stewart A et al. 2009
24. … Between Ganglion cells
• Ganglion-Ganglion gap junctions (fast
excitation < 2ms narrow spiking frequency
distribution).
• Ganglion-Amacrine gap junctions (slower
connections … broad distribution).
• Synchronization of spike outputs.
25. The aim of my PhD is to improve the
existent retina model (VirtualRetina) in
order to produce the retinal
synchronized output. How? … In the
discussion.
26. Circuit modeling of retinal function:
How to represent the retinal function
in simple electrical circuits?
• Light detection.
• Differential motion.
27. Light detection
At the post-synaptic gate of photoreceptor, we have: Signal + noise.
The synaptic connection between the photoreceptors and the bipolar cell is
equivalent to: A temporal filter followed by a threshold operation.
The filtered signals are given to the bipolar cell each through a dendrite connection:
The potential in the bipolar cell will be the summation of all these signals.
28. Differential motion
- Coding: Making the difference between the periphery signal (fb) and the
center signal.
- Same signal same motion. Different signal differential motion.
29. Virtual Retina
-Large scale simulation (> 10000
cells).
-Implementation of functional
retinal events.
-A compromise between
computational cost and biological
plausibility.
-Spike outputs are not
synchronized.
32. How to implement the
synchronization?
• Adding connection/Gap-Junctions between
Ganglion-Ganglion cells and Ganglion-
Amacrine cells.
• How to add these connection? Study the
statistics of real acquisition for vertebrate
retinas.
33. Adding connection holds two
possibilities
• Black box Add connections at the level of
ganglion cells without take into account the
connection between Ganglion and Amacrine?
• Adding both GG and GA physical connections?
34. Black Box
Rods-Cones
Horizontal
Amacrine
RGC
Adding connection between RGC: These
connection take (in a hidden way) the
connections between the RGC and
Amacrine.
35. Amacrine-RGC
Rods-Cones
Horizontal
Amacrine
RGC
Adding connection between RGC: These
connection take (in a hidden way) the
connections between the RGC and
Amacrine.
39. http://news.softpedia.com/news/Con
nections-Between-Retinal-Cell-
Population-Mapped-159743.shtml
• “Nobody has ever seen the entire input-
output transformation performed by complete
circuits in the retina at single-cell resolution,”
explains expert E.J. Chichilnisky, PhD.
“We think these data will allow us to more
deeply understand neuronal computations in
the visual system and ultimately may help us
construct better retinal implants,” adds the
scientist.