Ivan Izquierdo has made several key contributions to the understanding of the cellular basis of brain processes underlying memory storage and retrieval. His research work is focused in the biological mechanisms of memory processes, employing multiple experimental approaches that range from behavioral psychobiology to neurochemistry, pharmacology, neurophysiology and experimental neurology, usually employing intracerebral microinfusions of drugs and assaying its effects upon different brain receptors, cellular processes, and, in particular, behavioral performance in different tasks. He was among the first to reveal the roles of epinephrine, dopamine, endogenous opioid peptides and acetylcholine in modulating memory consolidation and state-dependent memory retrieval. Later he has investigated benzodiazepine and GABAergic influences on memory. Some of his main achievements include the molecular bases of memory formation, retrieval, persistence and extinction in the mammal brain, the endogenous state dependency, and the functional discrimination between short and long-term memory.