Quantification of the effects of cell ablation. A , Chemotaxis index showing the efficiency of chemotaxis. B , Weathervane index showing the extent of the weathervane response. C , Pirouette index showing the extent of the pirouette response. D , Basal frequency of pirouette at dC/dT = 0. E , Speed of locomotion. See Materials and Methods for definition of each index. Significant differences from the control (strains used for laser ablation, otherwise untreated N2 under standard assay conditions) are indicated by single asterisks (p < 0.05, t test), double asterisks (p < 0.01, t test) and plus symbols (p < 0.05, Bonferroni correction).