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DARPA Autonomous Vehicle
Grand Challenge 2003-2005
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BioRC Biomimetic Real-Time
Cortex 2006-
Reliable and Fault-Tolerant
Safety-Critical Systems
Nanoscale technologies can result in devices with
variable behavior
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Biological neurons do not fire with certainty and
sometimes fire spontaneously: outcomes can vary
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Ion Channel Variability in Axon Hillock
Synaptic Variability: Neurotransmitter Release Variability
In spite of variable behavior (random or chaotic)
individual biological neurons can be fault tolerant
Biological neural networks are redundant, reliable
and fault tolerant
WITHIN A NEURON (INTRANEURON):
BIOLOGICAL MECHANISMS LEAD TO
NEUROMORPHIC MECHANISMS
WITH A NEURAL NETWORK (INTERNEURON):
BIOLOGICAL MECHANISMS LEAD TO
NEUROMORPHIC MECHANISMS
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Multiple vesicles and receptors for each synapse
increase the probability of correct behavior even
if some mechanisms fail
NANOTUBE TRANSISTOR
(PARALLEL NANOTUBES FORM THE CHANNEL)
BUILT IN PROF. CHONGWU ZHOU’S NANOLAB
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Neuromorphic synapses can demonstrate
variable behavior that mimics vesicle and
receptor failure
Axon hillocks can demonstrate variable behavior
due to ion channel variability
Synaptic Circuit Results with and
without Variability
Dr. Jason Mahvash
n Synapse with no variability
n V_neuro is constant (750mv)
n Synapse with variability included
n V_neuro is a Gaussian noise
(mean=750mv, σ=50mv)
n PSP peak does not change.
V-neuro(v)
1
0.9
0.8
0.7
0
50
100
Time (ps)
150
200
Reliability of Spike Timing in Axon
Hillock Circuit (Mahvash)
Axon Hillock
(Ion-Channel
Variability
Included)
n Vth=170mv, Refractory period =100ps
n Constant PSP = 180mv
n Gaussian PSP generates spikes with more timing reliable
n Ion-channel variability is included (Gaussian)
Multiple synapses for each
presynaptic/postsynaptic neuron pair increase
the odds that the information is received by
the post synaptic neuron even if some
synapses fail
Redundant synapses, dendrites, axon hillocks can
form a single TMR neuron
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Signal persistence in post-synaptic potentials:
EPSP (excitatory +) and IPSP (inhibitory -) so
precise timing is not absolutely necessary
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Temporal Summation
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Superlinear responses in neurons to specific
input combinations of actively responding
synapses (dendritic spikes) allow a small
number of presynaptic neurons to invoke firing
in the postsynaptic neuron
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Dendritic spikes increase precision of subsequent
neural spiking
Input Jitter Impact on AP Spike Timing in Our Artificial Neuron
Dr. Chih-Chieh Hsu
No input jitter
0
0
20
20
40
40
Trial #
Ø precisely-timed
output spikes and
more resilient to
input jitter
Trial #
Neuron with
active dendrites
20 ps input jitter
60
80
100
0
80
50
100
150
200
250
Time (ps)
100
0
0
0
20
20
40
40
60
100
150
200
250
60
80
80
100
0
50
Time (ps)
Trial #
imprecise spiking
and less tolerant to
input jitter
Trial #
Neuron without
active dendrites
Ø
60
50
100
150
Time (ps)
200
250
100
0
50
100
150
Time (ps)
200
17
250
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Spiking patterns can be designed to ensure
postsynaptic neural response
Identical pathways in neural networks operate
properly even when individual neurons fail
Glial cells (astrocytes) interact with neurons
e.g. to induce synchronous firing that enhances
reliability
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There are 10 times as many glial cells as neurons in the brain
Glial cells control blood flow and propagation speed
Glial cells affect processing and memory
Astrocytes
Neurons
OUR EXCITATORY TRIPARTITE
SYNAPSE INCLUDING ASTROCYTE
WITH SLOW INWARD CURRENTS (SICS)
Postsynaptic
Presynaptic
Synapse Circuit
Presynaptic Side
APs
NT_Conc.
cleft
Postsynaptic Side
+
(3)
Delay
Reuptake
(1)
Receptor
EPSP
Delay
AstroCa2+
Astro_glut_release
Extrasynaptic
Side
Spread
(2)
BLOCK DIAGRAM OF A SMALL 2
NEURON NEURAL NETWORK WITH
ASTROCYTES
AP1_N1
AP2_N1
Presynaptic
Side
Postsynaptic
Side
Presynaptic
Side
Postsynaptic
Side
S1
EPSPs
Dendritic
Arbor
Extrasynaptic
NMDA (Fig.5)
Astrocyte
Microdomain_2
Fig.8
AP3_N2
AP4_N2
Total_EPSP_N1
Astrocyte
glioTs_M1
Astrocyte
glioTs_M2
Total_EPSP_N2
Extrasynaptic
NMDA (Fig.5)
S4
APout_N1
Extrasynaptic_side
S2
Astrocyte
Microdomain_1
Axon
Hillock
S3
Extrasynaptic_side
Presynaptic
Side
Postsynaptic
Side
Presynaptic
Side
Postsynaptic
Side
Dendritic
Arbor
EPSPs
Axon
Hillock
APout_N2
ASTROCYTE TEST BENCH
Two astrocytic microdomains connected to two networks are able to interact with
each other. The network connected to M1 spikes at a higher frequency and is able to trigger SICs (Slow Inward Currents) in both NTs
networks. NTs
N3
N1
SICs
M1
N4
N2
NTs
N7
N5
M2
SICs
N8
N6
NTs
SIMULATION RESULTS FOR NETWORK 2
NEURONS 7 AND 8
First, neurons 7 and 8 are unsynchronized, then we enable the astrocytes
To inject slow inward currents
EPSPs
and they
synchronize
JOSHI STRUCTURAL PLASTICITY
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Biological neural networks provide quasi-redundancy,
with multiple pathways arriving at a destination neuron
through performance of different but related
computations.
For example, recognition of a square shape
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recognition of many edges at specific locations and
orientations, or
recognition of 90 degree corners at specific locations.
Either approach could give provide square recognition,
Both in combination could provide recognition even
when part of the square shape is occluded or the image
is noisy.
WE CAN BUILD ELECTRONIC NEURONS AND PARTS OF NEURONS:
Ø WITH SYNAPTIC PLASTICITY – THE CONNECTIONS BETWEEN NEURONS
CAN CHANGE STRENGTHS
ØWITH STRUCTURAL PLASTICITY – NEW CONNECTIONS CAN FORM AND
OLD ONES CAN DISAPPEAR
ØTHAT DEMONSTRATE VARIABLE BEHAVIOR (STOCHASTIC AND CHAOTIC)
ØTHAT CONTAIN BOTH EXCITATORY AND INHIBITORY INPUTS
ØTHAT MIMIC RETINAL NEURONS WITH GRADED POTENTIALS
ØOUT OF NANOTRANSISTORS – CARBON NANOTUBES
ØTHAT COMMUNICATE WITH ASTROCYTES (A FORM OF GLIAL CELL )
ØWITH
DENDRITIC COMPUTATIONS – WE CAN ADD INPUTS IN
COMPLICATED MANNER, INCLUDING DENDRITIC SPIKING
ØWITH DENDRITIC PLASTICITY – THE ADDITIONS OF INPUTS CAN VARY
A
WE CAN BUILD SMALL NEURAL NETWORKS, INCLUDING MODELING OCD,
MS, SCHZOPHRENIC HALLUCINATIONS, C. ELEGANS TOUCH-SENSITIVE NW
DEMONSTRATE SELF AWARENESS
DEMONSTRATE ABSTRACT REASONING
DEMONSTRATE CONSCIOUSNESS
DEMONSTRATE THE ROLE OF EMOTIONS
DEMONSTRATE ALTRUISM
……..
§ Adam Levine @adamlevine Lead Singer, Maroon 5 on Twitter
§ “how awesome is it gonna be when we are updating the
software.......in our BRAINS.”
THANK YOU
Vref
dspike*
Sodium Spike
bAP*
Threshold
Adjustment
VDD
EPSP1
Vna
Vca-in
EPSP2
Na+
EPSP3
EPSP4
Calvl
6X
EPSP5
Calcium
Influx vss1
EPSP6
Apical/Basal
Branchi
vss2
X0
0.7
Basal1
Basal2
Apical1
Apical2
2X
2X
2X
VDD
VDD
Basalattn
Basal
VDD
VDD
VDD
2X
EPSPDDNx
IPSPBONy
Apical
Dendritic Potential (V)
VDD
VDD
0.6
VDD
0.5
0.4
4X
0.3
0.2attn
Apical
DD
PSPSOMA
4X
0.1
0
decreasing
spike threshold
V in dendrite
VDD
4X
0
4X
VDD
1
2
3
4
5
Number of Activated Synapses
6