Reivindicaciones

1. Use of a compound having the formula: <img class="EMIRef" id="588191205-ib0003" /> where A is -CO<2>H, or a pharmaceutically acceptable ester, amide, or salt thereof; and X is -NR<1>R<2> or a pharmaceutically acceptable acid addition salt thereof, and where R<1> and R<2> are independently selected from hydrogen or lower alkyl, optionally substituted with halogen, hydroxyl, alkoxy, oxo, mercapto, aryl, or amino, or R<1> and R<2> together with the nitrogen to which they are attached form a substituted 5-membered or 6-membered heterocycle which can also contain another heteroatom selected from oxygen, sulfur or nitrogen, which is a partial agonist for the strychnine-insensitive glycine site of the NMDA receptor due to a specific interaction with the receptor, and which acts as a functional antagonist of the strychnine-insensitive glycine site of the NMDA receptor complex by reducing or antagonizing the effects of glutamate or NMDA, in the preparation of a medicament for either improving or enhancing memory or cognition. 2. Use of a compound as claimed in claim 1, characterised in that the compound possessing partial agonist properties is selected from 1-aminocyclopropanecarboxylic acid or a pharmaceutically-acceptable salt, amide, and ester thereof. 3. Use of a compound as claimed in claim 2, characterised in that the compound possessing partial agonist properties is 1-aminocyclopropanecarboxylic acid.