Data for paper published in Science Advances A spreadsheet separated into tabs that contain all datasets for each related figure and supplementary figure. The datasets include behavioural measures of learning and the perception of training, and measures of neuronal activity based on electrophysiological recordings.    The tabs with datasets they contain are as follows:   TAB 1 relating to: Fig. 1. Previous strong learning enhances subsequent weak learning. Also Fig. S1, Fig. S2 and Fig. S3.  TAB 2 relating to: Fig. 2. Previous learning alters the perception of future training by shifting the network state. Also Fig. S4, Fig. S5, Fig. S6, Fig. S7 and Fig. S8.  TAB 3 relating to: Fig. 3. Learning-induced shift recorded in command-like interneurons controlling antagonistic behaviours.  TAB 4 relating to: Fig. 4. Characterization of perceptual control circuit that mediates competitive interactions between ingestion and egestion. Also Fig. S9.  TAB 5 relating to: Fig. 5. Pharmacological manipulation of perceptual control circuit substitutes for strong training and facilitates new memory acquisition in vivo. Also Fig. S10.  TAB 6 relating to: Fig. 6. Memory-linked shifts in perception generalize to an alternative training paradigm.  Abstract Long-term memory formation is energetically costly. Neural mechanisms that guide an animal to identify fruitful associations therefore have significant survival benefits. Here we elucidate a circuit mechanism in Lymnaea which enables past memory to shape new memory formation through changes in perception. Specifically, strong classical conditioning drives a positive shift in perception which facilitates the robust learning of a subsequent and otherwise ineffective weak association. Circuit dissection approaches reveal the neural control network responsible, characterized by a mutual inhibition motif. This both sets perceptual state and acts as the master controller for gating new learning. Pharmacological circuit manipulation in vivo fully substitutes for strong-paradigm learning, shifting the network into a more receptive state to enable subsequent weak-paradigm learning. Thus, perceptual change provides a conduit to link past and future memory storage. We propose that this mechanism alerts animals to learning-rich periods, lowering the threshold for new memory acquisition.