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The SBEs, as a trade mark of cultured networks activity, reflect the diversity
and complexity of the neuronal network. In most cases SBEs are a collective
phenomenon that involves the participation of almost all of the recorded neurons
and it is reasonable to assume that the whole network is activated. The internal
and spontaneous initiation of SBEs may be regarded as "natural" stimulation of
the network, as opposed to artificial stimulation such as by electrical pulses.
When there are multiple motifs of SBEs, such as often observed in large or
dissected cultures, each SBE motif may be treated as an outcome of a different
natural stimulation.
As was noted, most of the recorded cultures exhibited at least two sets of
propagation motifs. Patterned networks with large distances between culture
sections distinctively exhibit more burst motifs, proportional to the number of
sub-sections (Raichman and Ben-Jacob, 2008; Baruchi et al . In press). One clear
result of our analysis is the understanding of the contribution of spatial distance
between electrodes and the attribution of SBEs to different motifs, where
clustered networks significantly exhibit more motifs.
Previous works have shown that mature cultured networks exhibit a rich
repertoire of bursting patterns, where bursts vary largely in duration, intensity
and in the number of participating neurons (Kamioka et al . 1996; Mukai et al.
2003; Wagenaar et al . 2006). Large variations in network activity may also be
achieved by stimulation of the network (Gross et al. 1997; Jimbo et al . 1998;
Jimbo et al. 1999; Bi and Poo, 1999; Eytan et al . 2003; Bonifazi et al . 2005;
Chiappalone et al. 2007). This diverse form of activity may indicate that the
networks fire bursts repeatedly in different states, which are associated with the
different relaxation times and amount of accumulated neurotransmitters between
bursts.
We have also applied cold on our cultures in order to investigate methods for
neuro-protection. Low temperatures are a common tool used to protect the brain
during traumatic injury, patient recovery and surgical procedures. However, it is
known that some damage is caused to the cells under these procedures. Our
cultured networks offer a well controlled system for testing the effect of cold.
Our experiments, in which cold was applied to cultures for several hours,
show major and important results. The experiments clearly demonstrate that the
network survived hypothermia with little if any detectable changes to the
underlying neural network connectivity, exhibited by the protection of SBE
motifs by number and by structure. The same motifs that appeared before the
application of cold were also seen after the network stimulation. The strong
inhibition of our network activity during hypothermia may support and may help
to explain recent experiments in which cooling was used to arrest epileptic
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