Constructivists about memory argue that memory is a capacity for building representations of past events from a generalized information store (e.g., De Brigard, in Synthese 191:155-185, 2014a; Michaelian, in Philos Psychol 24:323-342, 2012). The view is motivated by the memory errors discovered in cognitive psychology. Little has been known about the neural mechanisms by which false memories are produced. Recently, using a method I call the Optogenetic False Memory Technique (O-FaMe), neuroscientists have created false memories in mice (e.g., Ramirez et al., in Science 341:388-391, 2013). In this paper, I examine how Constructivism fares in light of O-FaMe results. My aims are two-fold. First, I argue that errors found in O-FaMe and cognitive psychology are similar behaviorally. Second, Constructivists should be able to explain the former since they purport to explain the latter, but they cannot. I conclude that O-FaMe studies reveal details about the mechanism by which false memories are produced that are incompatible with the explanatory approach to false memories favored by Constructivism.