Fig. 2. Locomotor activity and temporospatial organization of trajectories in aged mice. (  A ) Distance moved in the open field before (baseline) and after anesthesia in aged mice. Anesthesia induced a reduction in distance covered in aged mice lacking the β²subunit of the nicotinic acetylcholine receptor (β²KO) (  P < 0.05) but not in aged wild-type (WT) mice (not significant). (  B ) Activity in the plus maze, expressed as number of transitions between the walled arms, was not significantly affected by genotype or by anesthesia in aged mice. (  C ) Spatiotemporal organization in aged mice. Aged β²KO mice also increased their exploration index 24 h after anesthesia compared with nonanesthetized controls (  C ,  left ) (  P < 0.05). Anesthesia affected the probability for venturing into the center of the arena (%PA-CA) (  P < 0.05) (  C ,  middle) . Statistical significance for planned comparisons between control and anesthesia groups is indicated  above the corresponding horizontal lines .Symbols within vertical bars indicate statistical significance for planned comparison with WT control. ko =β²knockout control group (n = 11); ko + sevo =β²knockout anesthesia group (n = 11); wt = wild-type control group (n = 7); wt + sevo = wild-type anesthesia group (n = 11). *  P < 0.05. -  P > 0.05.