Systems Biology (Methods in Molecular Biology)

transformations [14] the two types of agents in the shown simula-

tions have been characterized by both different color (yellow/blue)

and shape (regular/spiky). Due to the crucial influence on the cells

behavior attributed to a manifold of exogenous (environmental)

factors, it also appears of special interest the easy reproduction of

that influence by means of external force-fields, as exemplified in

Fig. 3. The aggregation induced by different force-fields on a

specific cell type is just one of the many relevant effects which

could be made more and more realistic as far as their type and

specificity is concerned. As a matter of fact, some relatively slight

improvements in the simulator would produce relevant predictions,

amenable to experimental tests. Such improvements mainly deal

with a precise modeling the influence of gravitational-fields, cell

density, and various chemical factors on the conformational switch.

2.2 Synchronized
Neurons

2.2.1 The Problem

A depolarizing wave moving at a 3 mm/min speed in the rabbits

cortex has been observed since a long time by Leao [15] and named

Cortical Spreading Depression (CSD), since after its passage the

cortex remained inactive for some time. In 1994, however, Laur-

itzen [16] showed that associated with the visual aura in human

migraine was a high-activity wave moving in the anterior direction

from the occipital region at speed from 2 to 6 mm/min. The

synchronous activity of large neuron patterns is triggered by the

synchronous activity in a relatively restricted area, which represents

the “epileptic focus.” From that area, the synchronous activity

spreads throughout the whole brain, so that an increasing number

of neurons become active at the same time. CSD is not limited to

the occipital area: its starting point may be observed most

Fig. 3Clustering of “regular” and “spiky” agents induced by specific force-

fields. The agents simulate a mixture of two (yellowandblue) cell types in a Petri

dish and the sources of the force-fields are indicated bysmalldots of the

correspondingcolor, outside the Petri dish

312 Alfredo Colosimo