Fig. 3.

Training in normal ASW produces differential enhancement of the synapse made by the CS⁺ sensory neuron. A, Representative records of the responses of the two presynaptic sensory neurons (bottom traces) and the postsynaptic motor neuron (top traces) during the second pretest and the 60 min post-test. Both tests were performed in 2:1 ASW (see Materials and Methods). B, Group data for experiments in which training was performed in normal ASW. The amplitude of the EPSP on each of the posttests was normalized to the amplitude of the EPSP on pretest 2 (see Fig. 2). The data are presented as means ± SEM. The EPSP in synapses that received paired CS–US stimulation (the CS⁺ group) was significantly enhanced compared with the normalized pretest EPSP (indicated by the dashed line). Furthermore, the CS⁺ EPSP was significantly more enhanced after training than was the EPSP in synapses that received unpaired training (the CS⁻ group; see Results).