Fig. 6.

Mean CA1 single neuron responses for the 20 sec trace conditioning group (top) and the matched pseudoconditioning group (bottom) on CS-alone trials. Histograms show single neuron activity in 500 msec bins averaged across the last three CS-alone trials during habituation (left), the first three CS-alone test trials of trace fear conditioning or pseudoconditioning (middle), and the first three CS-alone trials of retention (right). No significant group differences were revealed by average change score analyses, but the 20 sec trace group appears to show an increase in activity ∼20 sec after the offset of the CS on the initial CS-alone retention trials. Although no USs were presented on any of these CS-alone trials, the arrow marks 20 sec after CS offset, the time of US delivery during 20 sec trace fear conditioning (top middle). The duration of the CS was 3 sec.