Studies on the effects of estrogens show that they are critical for some aspects of cognition such as memory system bias in female rodents and women. However, less is known about progesterone which also has been implicated in the bias to use either place/spatial or response/habitual memory. Two subtypes of progesterone receptors have been identified: membrane-bound progesterone receptors and nuclear progesterone receptors. The purpose of this research is to map novel progesterone subtypes in areas of the female rat brain involved in multiple memory systems and examine the role of progesterone in memory bias within these brain areas.