Fake photos can create false memories. However, it has been unclear whether witnesses are able to reactivate their representations of original event details when seeing fake photos. This study investigated which brain regions reactivate neural signals of original event details when witnesses see fake photos. Functional magnetic resonance imaging data were obtained from 33 subjects at the original-event stage and the misinformation stage. Half of the subjects saw version A of the photos at the original-event stage and version B at the misinformation stage. The other half of the subjects saw version B of the photos at the original-event stage and version A at the misinformation stage. One day later, subjects completed recognition tests. To examine neural representations of event details shared across subjects at the original-event stage, we computed the neural pattern similarity between subjects who saw the same version and compared it to those who saw different versions. To investigate neural reactivations of event details, we computed the neural pattern similarity between subjects seeing the fake photo at the misinformation stage and other subjects seeing the original photo at the original-event stage. They were computed separately for subjects presented with the same version and for subjects presented with different versions, and the two were compared. When eyewitnesses first see an event, neural representations of the original event details in the visual cortex are shared between eyewitnesses, regardless of whether the later reported memory is true or false. However, when eyewitnesses are subsequently exposed to fake photos, their parietal cortex reactivates neural signals about the original event details, which may help to counteract image-based misinformation and thus report true memory. This finding has practical significance, as it demonstrates both the positive and negative effects that showing fake photos to witnesses can have on their memory.