Sensitization after Brief Pre-Exposure in a Moth Figure 4. Behavioural responses to linalool (A: LIN), geraniol (B: GER) and different concentrations of female pheromone extracts (C and D: PHE) of males pre-exposed to LIN, GER and PHE. Grey and black columns show the percentage of males walking towards and against the source, respectively. The length of the whole column (grey+black) shows their activity level. Within each frame (A, B, C, D), the percentage of PER responses were significantly different between columns with different letters (Chi-Square, p,0.05). The number of tested males is n = 30 for each column. Circular diagrams show the mean angle of individual males (the stimulus is situated at 0u). Asterisks in circular diagrams show groups of insects that showed non-uniform distributions (Rayleigh test, p,0.05). Sensitivity to LIN and GER did not vary with any kind of pre-exposure. Sensitivity to PHE increased with both LIN and GER pre-exposure. doi:10.1371/journal.pone.0034141.g004 Figure 5. Cumulative frequency curves of response thresholds for the main pheromone compound (Z,E-9,11-14:OAc) of intracellularly-recorded MGC neurons in na¨ıve (C(H20)) and pre-exposed (SUC) males. No significant differences between the sensitivity of na¨ıve and pre-exposed males were found, as revealed by a G-Test comparing the percentages of AL neurons responding at different thresholds. Note the bimodal distribution of thresholds in both groups: only few neurons with an intermediate threshold were found (flat curve between 1025 and 1022 ng doses). doi:10.1371/journal.pone.0034141.g005 PLoS ONE | www.plosone.org 6 March 2012 | Volume 7 | Issue 3 | e34141