Neurobiological studies of DID support the validity of the clinical diagnosis and suggest that one brain can generate two or more distinct states of self-awareness, each with its own unique pattern of seeing, thinking, behaving and remembering. Physiological markers such as changes in electrical skin conductance (related to sweating), heartbeat, response to medication, allergic reactions and endocrine function behave differently depending on which state the patient is in. For example, Simone Reinders and her colleagues at the University of Groningen in the Netherlands recorded subjective reactions (emotional, such as fear, and sensorimotor, such as restlessness), cardiovascular responses (heart rate, blood pressure and heart rate variability) and cerebral activation patterns in 11 DID patients. While the patients were first in one mental state and then the other, they were read a story from their life that pertained either to their trauma or to a nontraumatic autobiographical event. When in their neutral mental state, patients reacted to the story of their traumatic experience as if it were a neutral memory and claimed not to recall it; when in their traumatic personality state, they had a significant subjective and cardiovascular reaction to the traumatic memory and a different cerebral activation pattern, and they remembered the event. It appears that different identities can truly live inside the same skull.
To See or Not to See
Sometimes the difference between the personalities can be as stark as night and day. Psychoanalysts Bruno Waldvogel and Axel Ullrich and psychologist Hans Strasburger, all in Munich, Germany, reported a dissociated patient who gradually regained sight during psychotherapy—after 15 years of diagnosed blindness. There was nothing wrong with the patient’s eyes per se, but she claimed she couldn’t see, and testing at the ophthalmologist bore this out. During the experiment reported here, one personality state had essentially normal eyesight, whereas a younger, male personality—which could be summoned momentarily by calling out his name—was blind. This phenomenon could be construed as hysterical ranting were it not for the electrical activity recorded by electroencephalographic scalp electrodes. When in her sighted personality, the EEG showed normal brain waves in response to a checkerboard pattern that alternated its squares 10 times each second—from white to black and back again. But visually evoked activity was much reduced in her blind personality state. There is no known mechanism that allows someone to consciously block vision with open eyes. This remarkable finding implies that the brain can rapidly intervene at a very early stage of the visual system, preventing visual information from reaching the patient’s cortex. How it does so remains a mystery.
What may be altered in dissociative disorders is not so much the degree of activity of a particular brain area but the degree of interactivity between areas. Functional integration of cortical and subcortical regions is necessary for cohesive conscious experience. The way the brain is connected and the way different parts of the brain communicate with one another are important. Dissociation may be the result of a disruption of certain connections among brain regions. Hence, dissociative disorders may result from the failure of coordination or integration of the distributed neural circuitry that represents subjective self-awareness.
New advances in neuroscience and technology are revealing the neurobiology of the dynamic unconscious that Freud, Janet and others envisioned. In the process, inevitably, much of what was originally put forth based solely on the “talking cure” will be revised, refined and enhanced. Devising novel ways to empirically test dynamic unconscious processes such as repression, suppression and dissociation will reveal their neural bases. This effort will ultimately lead to more effective treatment options for psychiatric patients and help us to better understand our own consciousness.