Distribution of fast PSP amplitudes in B4/B5 from S1 neurons. Only EPSPs are present. Excitation increases after learning. As above, data are combined from all four subareas of the S1 cluster, and data are shown separately for the three stimulus trains of five spikes each and for the first (A) and fifth (B) PSP in a stimulus train. Naive animals, blue; animals that had learned, red. The lack of a connection (PSP amplitude of zero) is indicated by an unshaded bar. Asterisks show significant effects between naive animals and animals that had learned (see statistics in the text). Note color coding of the median values and asterisks, showing the values that were compared and found to be significantly different. The overall medians shown are the median amplitudes derived from averaging all three measurements for the first or the fifth PSP elicited by a stimulus train. Medians are shown in this and in subsequent graphs, rather than means, to reflect the use of nonparametric statistics that measure differences in ranking, rather than parametric statistics measuring values. N = 127 connections were sampled in 25 preparations from naive animals, and N = 174 connections were sampled in 31 preparations from animals that had learned.
