Impairment of the gustatory engram by generalised seizure activity without associated loss of conditioned taste aversion.

Three experiments are reported concerning the disruption of conditioned taste aversion (CTA) by generalised seizure activity (GSA) induced by electroconvulsive shock (ECS). Rats were taught CTAs by pairing either strong or weak taste cues (10% or 2.5% sucrose solutions) with either strong (0.15 M) or weak (0.05 M) doses of LiCl. In Experiment 1 it is shown that a 2.5% sucrose cue combined with a weak dose of LiCl will reproduce the disruptive effect of GSA when the CTA is established using a 10% sucrose cue. Likewise, a CTA acquired using a 2.5% sucrose cue paired with a strong dose of LiCl will simulate the failure of GSA to disrupt a CTA which has been established with a 10% sucrose cue. These findings support the theory that GSA acts to disrupt CTA by weakening the gustatory engram and an apparent inability to disrupt CTA by GSA does not necessarily signify that the gustatory engram itself remains intact. In Experiment 2, a CTA was established to a 2.5% sucrose cue using the more toxic dose of LiCl. It is shown that GSA will cause a substantial learning loss irrespective of whether it is interpolated within the taste-illness interval, or after the aversion has been acquired. It is concluded that the gustatory engram continues to reside in an active labile state even after the CTA has been established. In Experiment 3 it was estimated that the memory of the 2.5% sucrose cue must have been reduced to just over half of its original strength in order to create the learning loss reported in Experiment 2.