Planaria (Dugesia tigrina) are freshwater flatworms that are frequently studied because of their simple well-defined nervous system. Previous studies concluded that planaria can be trained to favor a direction in a Y- or T-maze using shock or other negative stimuli, but many of these experiments performed few overall runs and/or tested few individuals. The current study examines whether planaria have a directional bias and the ability to learn by using Y-mazes. The pre-conditioning period determined initial directional bias and was used to assign training directions. The conditioning period used electrical shock as a negative stimulus to condition planaria to select a specific turning direction in the Y-maze. Post-conditioning tested whether planaria maintained their learned behavior. Control planaria were not shocked during the conditioning period. Each period consisted of 3 trials with 10 runs in each trial. When examining the results of a single trial, many planaria demonstrated a directional bias. However, if individual trials for each experimental period were examined together, the majority of planaria were non-bias. Experimental planaria showed changes in their directional preferences during the conditioning period, but returned to their original bias, matching the controls, in post-conditioning. Planaria showed evidence of being trainable, but a total of 30 runs over 3 days may not be enough time for retention to occur.
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Vol. 79 • No. 4