Cells probe their surroundings. Gathering of global information.

[See ref 5 ]

Cells do not lose guidance at intersections between 'roads'. Instead, they examine their options

The cells in our guidance assay were not forced to follow the 'roads'. Therefore, we concluded that they were able to detect at least 2 points on the guiding 'road' and derive from their location a new heading. How powerful is their data processing method? Can 2 intersecting 'roads' throw them off course, because the cells would not know which 2 points to connect for a new heading? In order to answer this question, we offered the cells a grid pattern of intersecting 'roads' that were produced similar to our previous guiding assay. In the figure below, the grid pattern can be seen as a disturbance in the gold particle coat that we used to track the cells.

(The illustration is animated.Click here for a minimal strip of frames.)
Clearly, the cells did not lose their guidance at the intersections, but often they changed direction and followed a new road. Obviously, their processing method could distinguish between two different 'roads' and at least 4 different points when they 'computed' their new heading. But their processing system turned out to be much more powerful than that: At most intersections the tracks displayed little 'thorns' that stuck out sideways a short distance in all possible directions of the intersecting roads. Live cell observations like the one below offered the explanation:

(The illustration is animated.Click here for a minimal strip of frames.)
When the cells came to an intersection, they extended pseudopodia tentatively into the optional directions. In this way they removed the gold particles along the short extensions and produced the 'thorns' in their tracks. In other words, the cells were programmed to probe their options if guidance became ambiguous.

Significance for cell intelligence:

Cells are programmed to seek information about their spatial environment.
The probing behavior of the cells at intersections indicates a extraordinary high level of data processing. Not only can the cells override their internal movement programs, derive a new heading from spatially distant points of a 'road', and follow it. If they encounter more than one 'road' they are even programmed to explore their options. Still, even if we admit that such a data processing system must be highly complex, it does not answer the most tantalizing of all the question posed by this experiment: How did the cells know that they were at an intersection? Chapter 3 will try to offer a most startling answer that goes far beyond the quest for a navigational system of cells. I believe that the cells use their centrioles and near-infrared light to literally map and in a sense 'see' the space around them.