After catching my last few waves this morning, I'm now sitting at the computer evaluating the last weeks of research in the isolated leech nervous system. The main focus of the project was to do some pilot experiments towards establishing operant learning. I had done a quick-and-dirty evaluation last week already, but something didn't quite seem to fit, especially after taking the final week's worth of data and after eliminating all the preparations that didn't respond well to either anterior or posterior stimulation.

I ended up with a total of 13 preparations in three main groups: one experimental and two control groups. The two control groups consisted of one control group that did not receive any anterior stimulation at all, but was only observed for the 30 trials of posterior stimulation. The other control group was 'yoked' to preparations from the experimental group, i.e., they received anterior stimulations whenever the preparation in the experimental group received it, but irrpective of the motor pattern the animal actually was performing.

Each preparation then received ten posterior stimulations in a pre-test phase with no anterior stimulations. In the next phase, the training phase, all three groups received another ten posterior stimulations, but their anterior stimulations differed. In the experimental group, each preparation received contingent anterior stimulation on whatever was the most frequent motor pattern (swimming or crawling). The two control groups received either no anterior stimulation od yoked stimulations (see above). In the final test phase, all groups received the same ten posterior stimulations, without any anterior stimulation. This practice of making the anterior stimulation contingent on one of the two patterns during training means that each of the three groups can be further subdivided into two sub-groups: those who initially generated more swims and those who did the opposite.In theory, this means I have thus six groups. However, I didn't get any no-stimulatio controls whic responded with more crawls than swims in the pre-test, so I have a total of 5 groups.

You can follow my evaluations of the data below the fold:




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