The Physiologists FriendChip A product of the Institute of Neuroinformatics The only FriendChip...
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Transcript of The Physiologists FriendChip A product of the Institute of Neuroinformatics The only FriendChip...
![Page 1: The Physiologists FriendChip A product of the Institute of Neuroinformatics The only FriendChip youll ever need.](https://reader033.fdocuments.in/reader033/viewer/2022051613/55167600550346a2698b59bd/html5/thumbnails/1.jpg)
The Physiologist’s FriendChip A product of the Institute of Neuroinformatics
“The only FriendChip you’ll ever need”
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A Typical Visual Physiology Setup
Several communicating machines, custom software.Months of development and debugging…
Stimulus
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Goal
To make a practical chip that acts as a substitute animal for experiment design or demonstration.
• It should provide spiking neurons from retina and early visual cortex.
• It should be plug and play: •battery power
•no computer
•no knobs.
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Chip + LensChip + Lens
BNC connectorBNC connector
Volume Volume controlcontrol
Onboard speakerOnboard speaker
Output selectorOutput selector
External External speaker jackspeaker jack
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Chip schematic
Photoreceptors
Horizontal/Bipolar
GanglionSynapses
Photodiodes
Bias generator
34
1
25
6
7
8On Off
Excitatory
Inhibitory
Average
Brighter thanaverage
Darker thanaverage
Simplecells
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Layout
Photoreceptors
Bipolar/Horizontal cellsGanglion & Simple cells
Synapses
Photodiodes
2.2mm
Biases
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Photoreceptor layer
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Photoreceptor has low DC gain, high transient gain
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Adaptive Photoreceptor Circuit
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Vp
Vfb
Iphoto log I
V
Vp
Vfb
-UT/e-fold
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log I
V
Vp
Vfb Vout
Ib
Vp
Vout transient
Vfb
In steady state (DC)
V=0
TUC
CC
1
21 C2
C1
Long term history
of brightness
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Bipolar and Horizontal Layer
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Horizontal cell
Averages photoreceptor output
Vavg
Vphoto Vphoto Vphoto Vphoto Vphoto Vphoto Vphoto
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Horizontal cell
Using Deweerth’s follower aggegratorVphoto Vphoto Vphoto Vphoto Vphoto Vphoto Vphoto
Vavg
Averages photoreceptor output
Transconductanceamplifiers
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Bipolar CellRectifies into ON and OFF currents
Steals center part of diff pair current
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Ganglion cell layer
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Dendritic Trees of Simple Cells
ExcitatoryInhibitory
Are arranged to make orientation tuned simple cells with push-pull inputs
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PCBChip + LensChip + Lens
BNC connectorBNC connector
Volume Volume controlcontrol
Onboard speakerOnboard speaker
Output selectorOutput selector
External External speaker jackspeaker jack
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Spatial RFs of simple cellsMeasured by reverse spike correlation using
random orientation stimuli
Thanks to Matteo Carrandini
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Temporal and spatial frequency tunings of a simple cell
Thanks to Matteo Carrandini
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Chip design notes
• Chip simulation: 1s real time takes about 10h on P3 866MHz (TSPICE) – Simulations are very stiff numerically
• Cost: Chip ~$220, system ~$360. (dominated by cost of small quantity chip prototypes)
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SpecificationsPower supply 9V battery
9V DC supply (- on inside)
Power consumption External speaker: 2.5mA
Internal Speaker: 5 to 20mA
Lens 8mm focal length
Neutral density filter 1 decade filter behind lens temporally lowpass filters signal so chip can be used with monitor input
Tripod mount Standard 1/4” by 20 tripod thread
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Quick user guide 1Cell # Cell Type Output type
3 ON ganglion cell Spike
4 OFF ganglion cell Spike
7 ODD simple cell Spike
8 EVEN simple cell Spike
5 ODD simple cell Vmem
6 EVEN simple cell Vmem
1 Center Photoreceptor Vmem
2 Side Ganglion cell Vmem
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Quick user guide 2
• Things to be careful about:– Watch out for static electricity (ground yourself
before picking up the friendchip). Static can kill the chip!
– Store the friendchip in an anti-static bag– The lens holder is only attached with double
stick tape, it can be pulled off.
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What we plan
Complex cells
Direction selective cells
Production of ~100 systems for no-profit distribution to labs and teachers
(We have orders for about 30)
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