Temporal response patterns do not change with age. A, B, All units showed phasic-tonic response patterns classified as PL in approximately one-third of the units (CBA/J: 27%, C57BL/6J: 31%), and as PLN in the remaining units (CBA/J: 73%, C57BL/6J: 69%). Bin width 0.5 ms; in insets 0.2 ms. C, D, No systematic developmental change in the distribution of response types was found in either strain. The numbers of units are given as follows: n = #CBA/#C57BL.