Electrical hippocampal activity during danger and safety signals in classical conditioning in the rat.

The effect of stimuli predicting danger (DS) and safety (SS) in Pavlovian aversive conditioning on hippocampal local field potentials (LFP) was studied in 25 partially restrained adult male rats (Long-Evans). DS lasting 5 s preceded tail-shock, while SS overlapping DS during DS last 3 s predicted omission of shock. The power spectra of LFPs during trials were analyzed in theta and delta frequency bands. In DS, theta frequency during the last 3 s was lower that in first 2 s. In danger and safety situation theta peak frequency was different for dorsal CA1 activity (5.99 Hz vs. 6.86 Hz, respectively) while delta peak frequency was different for ventral CA1 (1.56 Hz vs. 1.07 Hz) for the last 3 s of trial. Differences in theta frequency in danger and safety situation may reflect differences in sensory processing during induced emotional states and/or related differences in motor behavior.