Cognitive dissonance is when you have two conflicting ideas and yet you have reasons to believe both. There are many many many reasons that appealing ideas can conflict, so we are constantly facing the prospect of cognitive dissonance, or more importantly how to resolve it.
What is the neural explanation for this common type of psychological stress? Thanks to advances in imaging methods, especially functional MRI, researchers have recently identified key brain regions linked to cognitive dissonance. The area implicated most consistently is the posterior part of the medial frontal cortex (pMFC), known to play an important role in avoiding aversive outcomes, a powerful built-in survival instinct. In fMRI studies, when subjects lie to a peer despite knowing that lying is wrong—a task that puts their actions and beliefs in conflict—the pMFC lights up.