It has been suggested that hippocampal activity predicts subsequent recognition success when recognition decisions are based disproportionately on recollection, whereas perirhinal activity predicts recognition success when decisions are based primarily on familiarity. Another perspective is that both hippocampal and perirhinal activity are predictive of overall memory strength. We tested the relationship between brain activity during learning and subsequent memory strength. Activity in a number of cortical regions (including regions within the "default network") was negatively correlated with subsequent memory strength, suggesting that this activity reflects inattention or mind wandering (and, consequently, poor memory). In contrast, activity in both hippocampus and perirhinal cortex positively correlated with the subsequent memory strength of remembered items. This finding suggests that both structures cooperate during learning to determine the memory strength of what is being learned.