Question

I am using a Conditioned Place Preference apparatus. It has three distinguishable chambers: a center chamber the subjects experience only on a test day and two conditioning chambers that differ only by the odors presented in each chamber (peppermint in Chamber A and licorice in Chamber B). I am using 40 rats in my project. Twenty of the rats will have a 2 milligram per kilogram dose of cocaine dissolved in sterile water injected on half of the conditioning days and sterile water injected on the other half of all conditioning days. The remaining 20 rats will receive an injection of sterile water regardless of which conditioning chamber they are placed in on any given day. All rats will be placed in Chamber A and Chamber B on alternating days. I want to be certain that neither order of treatments (cocaine versus sterile water) nor order of exposure to odors (peppermint versus licorice) is a relevant variable. Name the single most parsimonious and applicable control method that I can use?

Answer 1

THE CONDITIONED PLACE PREFERENCE:

The Conditioned Place Preference is based on Ivan Pavlov's Classical conditioning. The Conditioned Place Preference apparatus is used to identify the drug preferences in animals which could be found when the animals associate the drug's effects to the environment in which the drug given. The apparatus consists of 3 different chambers in which one is a neutral chamber, and the other two chambers differ from each other either by color, texture or smell.

In the above experiment, the first set of 20 rats are injected with cocaine and placed in chamber A, where the rat associates the effect of cocaine with the smell of peppermint in chamber A. And on next day these same rats are injected with sterile water and placed on chamber B, where there is no association as these rats do not have any drug effects. The same procedure is followed for alternate days.

The next set of 20 rats are conditioned in the same way, but the only difference is that the rats are given sterile water when they are placed in chamber A as well as in chamber B for the alternate days.

This experiment has both Experimental group and Control group, in which the same procedures are carried out for both the groups, with the difference that the experimental group had a treatment (injecting cocaine). And within the experimental groups also, the treatment was provided on alternate days. Thus, the experiment has minimum or no effects of extraneous variables such as the order of the treatment and the order of exposure to odours.