Memory of conditioned food aversion follows a U-shape function in rats

Rats drinking saccharin solution for the first time were poisoned by injection of lithium chloride and then offered saccharin solution 90 min, 1, 2, 3, 7, 10 or 14 days later. The memory function was U-shaped with 90-min and 14-day groups retaining the most aversion to saccharin. Intervention with an anticholinesterase (physostigmine) failed to produce a disruption or enhancement of memory, as might have been expected from theories that the laying down of memories depends on modification of cholinergic synapses.