What causes hallucinations: Mouse study uncovers unexpected changes in the brain's signaling

Scientists may finally be close to understanding the mechanisms behind hallucination. Despite the dramatic perceptual changes that take place during a bout of hallucination, what exactly happens in the brain during these moments has long been a mystery. A new study on drugged mice has found that the phenomena associated with these episodes may be the result of reduced signaling in the visual cortex – not an increase, as was expected. The images revealed that even after taking the drug, the signals being sent were largely similar to those seen in its absence, indicating that the information itself does not change. 'You might expect visual hallucinations would result from neurons in the brain firing like crazy, or by mismatched signals,' says senior author Cris Niell, an associate professor and member of the Institute of Neuroscience at the University of Oregon.