Neuroanatomy
A meta-analysis of structural MRI studies found an association with reduced total brain volume, intracranial volume, and volumes of the hippocampus, insula cortex, and anterior cingulate. Much of this research stems from PTSD in those exposed to the Vietnam War.People with PTSD have decreased brain activity in the dorsal and rostral anterior cingulate cortices and the ventromedial prefrontal cortex, areas linked to the experience and regulation of emotion.The amygdala is strongly involved in forming emotional memories, especially fear-related memories. During high stress, the hippocampus, which is associated with placing memories in the correct context of space and time and memory recall, is suppressed. According to one theory this suppression may be the cause of the flashbacks that can affect people with PTSD. When someone with PTSD undergoes stimuli similar to the traumatic event, the body perceives the event as occurring again because the memory was never properly recorded in the persons memory.The amygdalocentric model of PTSD proposes that the amygdala is very much aroused and insufficiently controlled by the medial prefrontal cortex and the hippocampus, in particular during extinction. This is consistent with an interpretation of PTSD as a syndrome of deficient extinction ability.The basolateral nucleus (BLA) of the amygdala is responsible for the comparison and development of associations between unconditioned and conditioned responses to stimuli, which results in the fear conditioning present in PTSD. The BLA activates the central nucleus (CeA) of the amygdala, which elaborates the fear response, (including behavioral response to threat and elevated startle response).
The primary dispute is between those who believe DID is caused by traumatic stresses forcing the mind to split into multiple identities, each with a separate set of memories, and the belief that the symptoms of DID are produced artificially by certain psychotherapeutic practices or patients playing a role they believe appropriate for a person with DID. The debate between the two positions is characterized by intense disagreement. Research into this hypothesis has been characterized by poor methodology. Psychiatrist Joel Paris notes that the idea that a personality is capable of splitting into independent alters is an unproven assertion that is at odds with research in cognitive psychology.Some believe that DID is caused by health care, i.e. symptoms of DID are created by therapists themselves via hypnosis. This belief also implies that those with DID are more susceptible to manipulation by hypnosis and suggestion than others. The iatrogenic model also sometimes states that treatment for DID is harmful. According to Brand, Loewenstein and Spiegel, "[t]he claims that DID treatment is harmful are based on anecdotal cases, opinion pieces, reports of damage that are not substantiated in the scientific literature, misrepresentations of the data, and misunderstandings about DID treatment and the phenomenology of DID".