Fig. 7. Effects of forward-pairing trials (A,B) and unpaired presentation of odours (C) on responses of the salivary neurones (SN1 and SN2). Summed responses of SN1 and SN2 to peppermint or vanilla odour before and at 5 min after the first, second, third and fourth sets of P+V- (A) or P-V+ (B) conditioning trials or unpaired presentations of odours (C) are shown. Relative responses, measured as the relative increase in spike frequency for the first 2 s of odour stimulation compared to that during a 2 s period before odour stimulation, are shown as means ± s.e.m.; N=20 (A,B), N=21 (C). Asterisks indicate the results of statistical comparison with responses to peppermint or vanilla odour before conditioning (NS, P>0.05; ^*P<0.05; ^**P<0.01; t-test).