We've all heard the argument that a subject under torture—or whatever this week's euphemism is—may begin fabricating whatever they believe the interrogator wants to hear just to get the agony to stop. Now neuroscientists are suggesting that inflicting too much pain and stress on a subject may not just induce them to lie; it may cause them to lose track of what's true and false altogether:
Fact One: To recall information stored in the brain, you must activate a number of areas, especially the prefrontal cortex (site of intentionality) and hippocampus (the door to long-term memory storage). Fact Two: Stress such as that caused by torture releases the hormone cortisol, which can impair cognitive function, including that of the prefrontal cortex and hippocampus. Studies in which soldiers were subjected to stress in the form of food and sleep deprivation have found that it impaired their ability to recall personal memories and information, as this 2006 study reported. "Studies of extreme stress with Special Forces Soldiers have found that recall of previously-learned information was impaired after stress occurred," notes O'Mara. "Water-boarding in particular is an extreme stressor and has the potential to elicit widespread stress-induced changes in the brain."
Stress also releases catecholamines such as noradrenaline, which can enlarge the amygdale (structures involved in the processing of fear), also impairing memory and the ability to distinguish a true memory from a false or implanted one. Brain imaging of torture victims, as in this study, suggest why: torture triggers abnormal patterns of activation in the frontal and temporal lobes, impairing memory. Rather than a question triggering a (relatively) simple pattern of brain activation that leads to the stored memory of information that can answer the question, the question stimulates memories almost chaotically, without regard to their truthfulness.
In brief, the subject may lose genuine memories, and come to believe that their confabulations are authentic ones. The full literature review, from Trends in Cognitive Science, can be downloaded in PDF form here.