Development of maximum evoked discharge rates. A, Both strains (CBA/J: filled circles; C57BL/6J: open circles) showed an increase in maximum discharge rates with age (p < 0.001; ANOVA; black and white solid lines, exponential fit). B, No discernable correlation was found between the units' maximum discharge rates and the CFs (CBA/J mice, circles; C57BL/6J mice, triangles; ages as indicated by different shades of gray; numbers of units at different ages: n = #CBA/#C57BL).