Biomedical Engineering Reference
In-Depth Information
record spatiotemporal maps of signal propagation in the neurites and concluded that the non-
isopotential model deviated from the synaptic conductance estimates of the isopotential theory
by approximately 13%, which is not negligible.
Eshel Ben-Jacob's group from Tel-Aviv University in Israel has been able to induce collec-
tive modes of neuron iring in the activity of cultured (randomly organized) neural networks
(
Figure 6.65
). he recordings are performed via a standard MEA and stimulation of selected
neurons is performed by injecting microdroplets just above the desired locations. According to
Ben-Jacob, previous attempts to trigger memories in neuronal networks in vitro failed because
they focused on excitatory neurons, which resulted in randomly escalated activity that does not
mimic what occurs when new information is learned. In this study, microdroplets of inhibitory
antagonist (picrotoxin, an antagonist of
GABA
, the primary inhibitory neurotransmitter) were
delivered locally instead. he chemical suppression of the inhibitory neuron created a pattern
kicked of by a neighboring excitatory neuron that was now free to ire. Other neurons in the
culture began to ire one by one as they received an electrical signal from one of their neighbors.
his continued in the same pattern, which repeated for over a day. his new sequence of activity
coexisted with the electrical pattern that was spontaneously generated when the neural culture
was initially linked (correlation matrix in
Figure 6.65f
). A day later, they imprinted a third pat-
tern starting at a diferent inhibitory synapse (correlation matrix in
Figure 6.65e
). Surprisingly,
it was able to coexist with the other motifs, showing that chemical signaling might play a crucial
role in memory and learning.
a
Pipette
b
Pipette
200 µm
Stimulated neuron
Stimulation
1
8
15
15
c
d
10
Action
potentials
22
29
36
5
0
0.5
1
1
100 200
Time [min]
300
Time [sec]
e
f
g
1
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
0.8
0.6
0.4
0.2
0
FIGURE 6.65
Using.multielectrode.arrays.to.study.neural.networks.in.vitro..In.(c),.each.row.is.a.
binary.bar.code.representation.of.the.activity.of.a.different.neuron,.and.a.bar.is.plotted.each.time.
the. neuron. ires. an. action. potential.. The. time. axis. is. divided. into. 10-ms. bins.. One. injection. is.
suficient.to.initiate.a.single.synchronized.bursting.event.with.a.distinct.pattern.of.neuronal.iring..
(From.Itay.Baruchi.and.Eshel.Ben-Jacob,.“Towards.neuro-memory-chip:.Imprinting.multiple.memo-
ries.in.cultured.neural.networks,”.
Phy. Rev. E
.75,.050901(R),.2007..Copyrighted.by.the.American.
Physical.Society..Figure.contributed.by.Eshel.Ben-Jacob.)
