Sequence-related changes in sensory-evoked potentials in the dentate gyrus: a mechanism for item-specific short-term...

Sensory-evoked potentials were recorded from the dentate gyrus of the rat hippocampus during performance of a differential auditory discrimination task. The short latency (20 ms) component (N1) of the sensory-evoked potential showed systematic amplitude fluctuations dependent upon the sequence of positive and negative trials preceding the presentation of a given trial and did not depend on the associated reward values of the individual tone stimuli which evoked the potential. The amplitude fluctuations could be accurately depicted by a model which retained the sequence for the five preceding trials in a "buffer" with exponentially decaying influence as a function of time of trial occurrence within the sequence. The results provide evidence that the hippocampus encodes accurate short-lasting representations of sensory events which can provide the basis for storage of information pertaining to past experiences.