Nature 390, 604–607; 1997

In Fig. 1a of this Letter, the labelling for the control rat (bottom panel) was erroneously relettered as ‘Unpaired/Paired/Paired’, whereas it should have read ‘Unpaired/Unpaired/Unpaired’.

Also, the report of raw (not normalized) values of slope and amplitudes before training (third paragraph) should read ‘slope: conditioned group, −1.649 ± 0.425 μV ms−1, control group, −2.329 ± 0.346 μV ms−1; t-test, P > 0.05; amplitude: conditioned group, 14.186 ± 4.103 μV, control group, 18.116 ± 4.214 μV; t-test, P > 0.05)’. Finally, on the third line of page 606, P < 0.01 (not >0.01 as published).