The Reversal Potential of Inhibitory Synapses Strongly Impacts the Dynamics of Neural Networks - Foundations on Natural and Artificial Computation - page 105

Fig. 1. Synchronization properties of pyramidal neurons and FS interneurons in ab-
sence of coupling between the two networks ( g FP = g PF = 0). Left panel: g e =0,

=3 . 5 μA/cm 2 , I F =1 . 3 μA/cm 2 , N PY = 80,

g i

=0, g el =0, I P

N FS = 20. Middle

=0 . 2 mS/cm 2 , g i =0 . 25 mS/cm 2 . Right panel: panel: as the left panel except for g e

=0 . 5 mS/cm 2 , =0 . 25 mS/cm 2 , =0 . 1 mS/cm 2 .

as the left panel except for g e g i g el

η P = η F =0 . 2 μA/cm 2 . For all panels the gray vertical bars
represent the firing times of the pyramidal cells, while the black ones those of the FS
interneurons.

The noise amplitudes are

discharges of the inhibitory cells increases. The results plotted on the middle
panel of figure 2 show that not appreciable change on the firing activities of
pyramidal cells occurs when the inhibitory synapses from FS interneurons to
the excitatory network are set on (see for comparison the results reported in the
right panel of figure 1). When it is g FP

= 0 the bursting activity
in the network of excitatory cells in almost abolished and the cells fire nearly
synchronously. The effect of the reciprocal coupling between the two networks
leads to a little increase of the synchrony levels among inhibitory cells. Moreover
there is a partial phase locking regime between excitatory and inhibitory cells
and this behavior arises as a consequence of the reciprocal coupling between the
two networks.

=0and g PF

3.2 Reversal Potential of the Inhibitory Synapses and Networks

Dynamics

The results of several experimental investigations have shown that seizure af-
terdischarges induced by electrical stimulation promotes the accumulation of
intracellular Cl − . In these conditions inhibitory GABAergic synapses on pyra-
midal cells exert a depolarizing action. This phenomenon also occurs among FS
interneurons: i.e. the inhibitory synapses connecting the cells of this network
become depolarizing [6,7]. This phenomenon is driven by the reversal potential
value of GABAergic synapses [7]. In our computational approach we studied
how the change of the reversal potential value of GABAergic synapses affects
the dynamics of the pyramidal and FS cells networks.