Synaptic plasticity, the ability of neurons to alter the strength of their synaptic connections with activity and experience, is thought to play a critical role in memory storage. Molecular studies of gene expression during long-lasting synaptic plasticity related to memory storage initially focused on the identification of positive regulators. More recent work has revealed that the establishment of long-lasting synaptic plasticity and long-term memory also requires the removal of inhibitory constraints. By analogy to tumor supressor genes, which restrain cell proliferation, we propose that these inhibitory constraints on memory storage, which restrain synapse growth, be termed memory suppressor genes.