Whisker stimulation is an effective conditioning stimulus (CS) for trace eyeblink conditioning (EBC) in rabbits. The whisker-CS is of interest for the study of learning and memory, given learning-specific metabolic changes observed in our laboratory in the somatotopic map of the whisker barrel field cortex (Galvez et al, SFN Abs 2005). In the present study, we sought to determine whether the hippocampus, critical for the acquisition of trace EBC, exhibits single neuron activity changes in vivo with a whisker-CS similar to those observed during tone-CS trace EBC. A total of 38.1% (82/215) of CA1 pyramidal neurons from 3 trace conditioned rabbits exhibited significant increases in activity (z>1.96) during CS (250ms), trace (500ms), US (150ms) and/or post-US (1000ms) intervals compared to baseline (1000ms). Stimulus-evoked responses developed as early as the first day of training (80 trials/session, mean trials to initial conditioned responses: 124±81, S.E.). The evidence for stimulus-evoked increases in firi...