How do you know what’s real? A new study suggests that people’s ability to distinguish between what really happened and what was imagined may be determined by the presence of a fold at the front of the brain that develops late in pregnancy, and is missing entirely in 27% of people. Although the study sounds like it sprouted from the musings of stoned undergraduates or the abstruse pursuits of basic-neuroscience geeks, its findings may prove important for the understanding of schizophrenia, a disorder which often includes confusion between real and imagined voices. The key brain structure identified by the study is called the paracingulate sulcus (PCS), a fold in part of the prefrontal cortex, the region that is involved with planning, thought and judgment. The size of the PCS varies greatly in normal people, and some people a PCS only on one side of their brain, while others have one on both. Compared to the quarter or so of healthy people who are completely missing the PCS, 44% of people with schizophrenia do not have it, suggesting that its absence could play a role in the disease. But the new study found that even normal people without the PCS have difficulty distinguishing between what they remembered and what they imagined. MORE: Why Pot Smokers Are Paranoid The researchers studied 53 healthy volunteers, chosen because brain scans showed they had a prominent PCS, no PCS, or were missing it on either side of the brain. Participants were presented with either recognizable word-pairs like “Laurel and Hardy” or the first word in a common word-pair, such as “Laurel and ?” When only half the word-pair was provided, participants were asked to imagine the second word. Sometimes, the volunteers were then asked to read the words out loud. In other cases, the words were read to them by an experimenter. Afterward, all participants were given a memory test in which they were asked whether they had seen or imagined the second word of each word-pair and also whether it was they or the … Continue reading Reality Check: Why Some Brains Can’t Tell Real From Imagined