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Using Nanotechnology to Understand
How the Brain Computes Jacob T. Robinson
Rice University
Electrical and Computer Engineering
Bioengineering
The scales of neural computation!
Single cells Micro circuits 10 µm T. Branco et al., Science 329: 1671 (2010) 1 neuron robinsonlab.com
Macro circuits 1 mm 100 μm D. Schubert, et al., Brain Struct.& Func. 212, 107 (2007) 10 – 10,000 neurons Desai M et al., J Neurophysiol 105, 1393 (2011) 1 voxel ≈ 10,000 neurons Neural computation for mental health!
April, 2nd 2013 robinsonlab.com
Neural computation for technological
inspiration!
Deep Blue: 1997!
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Watson: 2011!
Watson vs. human!
Waston’s “brain” Ken Jennings’ brain Power consumpFon ~350kW ~150W Switching speed ~3GHz ~100kHz Fits in a… Room Bucket Number of switches ~1015 ~1011 Gates per switch 1 ~104 Architecture Sta9c Dynamic robinsonlab.com
Dynamic neural connections !
Steve Smith’s Lab, Stanford!
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Changes in neural connections underlie
learning & memory!
•  Hebb’s Postulate (1949): When cell A repeatedly
excites cell B and participates in firing it, the
connection between A and B becomes stronger.!
a
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wab
b
dwab
τw
= ab
dt
Learning in artificial networks!
u1
u
w
w
u2
v
dw
τw
= vu
dt
Adapted from Dayan and Abbott!
# +1 if
v =%
% −1 if
$
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w•u −γ ≥ 0 &
(
w • u − γ ≥ 0 ('
Do real networks learn according to
Hebbian learning rules?!
u
Need to measure: w
v
Adapted from Dayan and Abbott!
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v(u)
What has the network “learned”? w(t)
How did the synapses adapt to encode this memory? Synaptic “weight”!
u1
w1
… wn
un
PresynapFc v
Action Potential!
PostsynapFc Vth current Challenge: How to measure and manipulate voltage in hundreds of cells?!
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Scale of cells and cell networks!
Cell!
~101-106 cells!
~1011 cells!
Network!
Organ!
~1013 cells!
System!
1!
Transistor!
Integrated circuit!
Processor!
~101-106 transistors!
~109 transistors!
Laptop!
~1010 transistors!
Silicon nanotechnology: ideal platform for next-generation neural interfaces!
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Vertical silicon nanowires (NWs)!
Small and Scalable!
Tunable geometry!
Scalable production!
(Length, Density, Diameter)!
(4” & 6”wafer-scale)!
NW diameter << Cell diameter!
10 µm 2 µm 25 mm 2 µm robinsonlab.com
0.1 µm A.K. Shalek, J.T. Robinson et al., PNAS 107, 1870 (2010)!
Vertical silicon NWs penetrate cells!
1 µm!
P. Yang Lab, Berkeley!
L. Samuelson Lab, Lund!
Kim et al., J. Am. Chem. Soc., 129, (2007)!
Hällström et al., Nano Lett, 7, (2007)!
C. Lieber Lab, Harvard!
H. Park Lab, Harvard!
Tian et al., Science 329, 831 (2010)!
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A.K. Shalek, J.T. Robinson et al., PNAS 107, 1870 (2010)!
NWs: intracellular interface!
Electrical probes!
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NW electrode arrays in silicon!
1µm Metal-tipped NWs!
10µm Highly-doped SOI!
Insulated pads!
100µm 16 individual
electrode pads!
Rat corFcal neuron J. T. Robinson, M. Jorgolli, et al. Nature Nano 7, 180 (2012)!
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Excite & measure activity of
individual neurons!
Rat Cortical Neuron!
NW stimulation!
NW recording!
10 µm Scalable intracellular neural interface!
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J. T. Robinson, M. Jorgolli, et al.
Nature Nano 7, 180 (2012)!
Determine neural connectivity!
Excitatory Not connected t0 t0 t1 t2 1 t1 t2 2 VNW Inhibitory t0 t1 t2 3 VNW 4 VNW 16 VNW NW sFmulaFon “output” neuron t0 t1 t2… Patch recording robinsonlab.com
VNW Reconstructing neural circuits!
Record one “output” neuron!
Systematically stim 16 inputs!
35 µm Direct connection
(monosynaptic) !
Record PSPs!
120 µm Polysynaptic or!
spontaneous PSPs!
Functional connectivity map!
05 NW pad!
12 13 14 15 05 12 13 14 15 5 ms 15 ms PSP Latency!
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25 ms J. T. Robinson, M.
Jorgolli, et al. Nature
Nano 7, 180 (2012)!
Efficient circuit reconstruction!
Stimuli!
cell #!
1
2
w
N!
trials!
v
trial #!
u
N
M<N
trials!
trial #!
cell #!
Pooled Stimuli!
Measured
Response!
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Patterned Activation of Neurons!
Optical Stimulation of APs!
F. Zhang et al., Nat Rev Neurosci 8, 557 (2007) robinsonlab.com
Patterned Activation of Neurons!
Optical Stimulation of APs!
Digital
Micromirror
Device
F. Zhang et al., Nat Rev Neurosci 8, 557 (2007) robinsonlab.com
Dichroic
filter cube
Objective
Lens
z
y
Neuron culture
x
Toward in vivo network studies!
Zebrafish Larvae!
C. Elegans!
1 mm!
A. Pan, Harvard!
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0.25 mm!
J. Scholey, UC Davis!
Neural Connectivity Map of C. Elegans !
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Toward in vivo network studies!
NW electrodes robinsonlab.com
Acknowledgments!
Harvard:!
!
Hongkun Park!
Marsela Jorgolli!
Alex Shalek!
Rona Gertner!
Jellert Gaublomme!
!
Thorsten Schlaeger (HSCI)!
!
James MacArthur (Physics Electronics Shop)!
Louie DeFeo (SEAS Machine Shop)!
Edward Soucy (Center for Brain Science)!
Joel Greenwood (Center for Brain Science)!
Funding:!
NIH Pioneer!
NSF EFRICOPN!
SPARC!
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Rice:!
!
Ben Avants!
Martin Bell!
Marissa Garcia!
Spencer Kent!
Dan Murphy!
Rahul Roy!
Daniel Vercosa!
!
Rich Baraniuk!
Eva Dyer!
!
Gary Woods!
!
Others:!
Eun Yang (KIST, Korea)!
H. Sebastian Seung (MIT)!
Neville Sanjana (MIT)!
!
Senior Design Team:!
Duffy Elmer !
Dong Kyu Kim !
Carolyne Ma!
Storm Slivkoff !
CJ Williams!
!
!
WeiWei Zhong!