(A) Behavioral reactivity scores and (B) number of fecal boli per day of the five Mn exposure groups across the three stages of the staircase study (stage I, II, and III, corresponded to day 1-8, 9-20, and 21-25 of the study, respectively). Daily scores were averaged across days per rat; bars/symbols represent the mean ±S.E. (n=11-12/group). *p<0.05 relative to the control group. Manganese doses in mg Mn/kg/d (see text).