FIGURE 4.

The effects of pollen and Nosema ceranae on odor learning and memory at Day 7. Proboscis extension response (PER) was measured among four groups of bees including: bees pollen (N = 39, 38) and N. ceranae-infected bees pollen (N = 30, 38). The PER response of each group was tested as bees were trained to associate an odor with a reward (Trial Learning, A). Memory retrieval (B) of the conditioned stimulus was measured 10 min after trial learning by presenting the odor alone. Significance(^∗) was determined using separate Wilcoxon tests for Trial 2, Trial 3, and Memory Retrieval. Groups connected by the same letter are not significantly different.