Wednesday, 3 June 2009

13. Formal inversion in C. elegans - D.

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[Diagram developed from data published by White et al. (1986).]

The circuit illustrates some of the fundamental workings of the worm homologue of our human cerebral cortex. As an informal description of the circuit's activity, the worm in the diagram may be envisaged as having a 'minimal model thought' concerning taste.

Two main sensory cells for taste (at the top of the figure) are called ASE. The left is ASEL and the right ASER. When the worm detects certain chemicals in the outside world, signals flow in the direction of the arrows.

The sensory neurons connect with interneurons called AIB (left and right again). Note that at this stage the signals change direction. The previously clockwise left signals now travel anticlockwise, and the inverse is the case on the other side. Note also that in making the connections at this level, the ASEL-AIBR connections are one-way and that the ASER-AIBL connections are two-way or circular. The latter pattern is emphasised in the upper right dotted yellow box.

How have these patterns been revealed? By use of a newly developed technique called a connectogram, which will be illustrated in the next picture.

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