(A) Chemotaxis performance of wild-type worms from young adulthood (day 1) through early stage aging (day 6) towards a point source of medium BZ. (B) Speed of wild-type young (day 1) and aged (day 5) adult animals chemotaxing towards a point source of BZ odor. (C–F) Heat maps of ratio change in fluorescence to total fluorescence for wild-type young adult (day 1) and aged adult (day 5) sensory neuron responses to the addition (at t = 10 s) or removal (at t = 130 s) of a two-minute medium BZ stimulus (0.005% vol/vol), as indicated by shaded box and arrows. One row represents activity from one neuron. (G) Maximum ΔF/F for each individual young (black dots) or aged (blue dots) wild-type animal shown in C–F. (H) Averaged ΔF/F after odor addition (for AWA) or odor removal (for all other neurons) for each individual young (black dots) or aged (blue dots) wild-type animal shown in C–F. The red line represents a ΔF/F of 10%, the cutoff used to classify neurons as odor responsive or non-responsive. *p < 0.05, two-tailed t-test comparing young and aged responses; statistical analysis performed only on odor responsive subset of data. (I) Quantification of the percent of odor responsive neurons shown in H. (J) Aged (day 5) adult BZ chemotaxis performance of wild-type, AWC or AWB or ASH neuron-specific genetic ablation, AWA neuron-specific tetanus toxin expression worms or che-1 mutants missing ASE neurons. (K, L) The percent of wild-type young (day 1) and aged (day 5) adult (K) ASEL neurons responsive to sodium chloride and (L) AWB neurons responsive to 2-nonanone odor. (I, K, L) Odor or salt responsive defined as having a ΔF/F to stimulus greater than 10%. Numbers on bars indicate number of neurons imaged. *p < 0.05, two-tailed Chi Square test. (A, B, J) Numbers on bars indicate number of assay plates and error bars indicate s.e.m. *p < 0.05, two-tailed t-test with Bonferroni correction, compared to young adults or wild-type as indicated. See Figure 5—source data 1 for raw data.