Methylphenidate treatment is used for Attention Deficit Hyperactivity Disorder and can improve learning and memory. Previously, improvements were considered a by-product of increased attention; however, we hypothesize that methylphenidate directly alters mechanisms underlying learning and memory, and therefore examined its effects on hippocampal long-term potentiation and long-term depression. Methylphenidate enhanced both mechanisms in the absence of presynaptic changes and in a noradrenalin [beta]-receptor-dependent manner. These findings can explain both the improved learning and memory and decreased learning selectivity found with methylphenidate treatment and constitute the first demonstration of direct actions of methylphenidate on mechanisms implicated in cognition.