Figure 7.

Learning impairment after IPA exposure is not due to decreased sucrose responsiveness. Distribution of bees exposed to isopentyl acetate (IPA) or mineral oil (Oil) according to SRS (sucrose response score) values. Unconditioned responses elicited by sucrose were assessed, using 6 sucrose solutions of increasing concentrations (0.1, 0.3, 1, 3, 10, and 30%, in water). For each animal, the presence or absence of a PER was recorded for each concentration, and its individual SRS was calculated as the number of stimuli eliciting a PER (e.g., SRS = 3 for an individual responding to 3, 10, and 30% sucrose but not to lower concentrations). The number of bees with a given value in each group is indicated by the number on each bar. Among bees showing motivation to respond to sucrose, no difference was found between the two groups (χ² = 3.68, df = 3, p = 0.30; bees with SRS values higher than three were grouped in a single category to allow the use of the chi-square test, see Materials and Methods). NS: non-significant.