Biomedical Engineering Reference
In-Depth Information
Despite the latest achievements about the
astrocytes, there is not exact information about
their influence on brain processing or about the
regulation of the astrocyte-neuron communication
and its consequences.
Artificial models of neuroglial circuits have
been developed as an attempt of studying the
effects of the neuroglial activity that have been
observed until now at the Neuroscience labo-
ratories (Pasti et al., 1997; Araque et al., 1999;
Araque et al., 2001; Perea & Araque, 2002; Perea
& Araque, 2005, Martin & Araque, 2006), as
well as of giving expression to the hypothesis
and phenomena of these activity. In that way,
the initially performed works have involved the
elaboration of a ANGNs building methodology
(Porto, 2004). The essence of this methodology,
its application to classification problems and the
latest results achieved after mimicking different
functioning options of the Artificial NeuroGlial
Networks are shown in the present chapter. The
implementation of the mentioned options enables
the study of these networks from the Artificial
Intelligence viewpoint and the application of the
ANGNs for solving real problems.
group from the University of A Coruña performs
two interrelated research works from the view-
point of Computer Science. One of these types
involves the elaboration of “biological” compu-
tational models to reach a better understanding
of the structure and behaviour of both neurons
(LeRay et al., 2004, Fernández et al., 2007), and
astrocytes (Porto, 2004). The second type of works
considers behaviour observed in the brain circuits
and the studied biological phenomena in order to
create CSs; these systems should test if the pres-
ence of such phenomena provides advantages for
information processing (Porto et al., 2005; Porto
et al. 2006, Porto et al. 2007). No actualised
publications of other research groups have been
found regarding the later works, although some
first attempts of incorporating the astrocyte func-
tions are appearing, as the work of Xi Shen &
Philippe De Wilde (2006). These authors model
the increase of the blood flow within the brain
capillary vessels according the neuronal activ-
ity and the neuron-astrocyte pairing; however,
it is only a mathematical modelling that does
not use the knowledge about astrocytes on the
implementation of CSs.
Also Nadkarni et al. (2007) elaborated a math-
ematical framework, apart from the connectionist
models, for modelling the synaptic interactions
between the neurons and the astrocytes, bearing
in mind the tripartite synapse concept (Araque et
al., 1999). This model also includes the quantita-
tive description of the experimental conclusions
related to the synaptic boosting and to the increase
of spontaneous postsynaptic currents that occur
when astrocyte activity is involved (Liu et al.,
2004) (Fiacco et al., 2004). This model tries to
provide a conceptual basis for more complex ex-
perimental protocols, as it quantifies an adaptive
synapses that changes its reliability depending on
the astrocyte behaviour. The intervention of the
astrocytes can modulate a neuron network and its
subsequent activity by providing other capabilities
and an additional plasticity that it would not exist
in absence of the glial cells.
bACkGROUND
The specific association of processes with syn-
apses and the discovery of two-way astrocyte-
neuron communication (Perea & Araque, 2005)
have demonstrated the inadequacy of the previ-
ously held view regarding the purely supportive
role for these glial cells. Instead, future progress
requires rethinking how the dynamics of the
coupled neuron-glial network can store, recall,
and process information.
It is a novel research field that is here covered
from the Artificial Intelligence viewpoint; no CS
considering the glial system had been developed
ever before.
In this regard, the RNASA (Artificial Neural
Networks and Adaptive Systems) laboratory, our
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