Benedict Carey at the Times has an interesting article documenting the harrowing story of Adam Lepak, who has struggled with identity delusions since 2007, when he was involved in a serious motorcycle accident:
The diagnosis [given to Adam] was diffuse axonal injury. “The textbook definition is essentially a blow that shuts down the bundle of wires responsible for keeping us conscious,” said Dr. Jonathan Fellus, a neurologist at Kessler Institute for Rehabilitation in West Orange, N.J., who has overseen Adam’s gradual recovery. “It’s as if the major highways have taken a hit, and now the brain has to use back roads to function. But every brain responds differently. I have given up making predictions.”
Researchers who have taken images of the brain as it processes information related to personal identity have noticed that several areas are particularly active. Called cortical midline structures, they run like an apple core from the frontal lobes near the forehead through the center of the brain.
These frontal and midline areas communicate with regions of the brain that process memory and emotion, in the medial temporal lobe, buried deep beneath each ear. And studies strongly suggest that in delusions of identity, these emotion centers are either not well connected to frontal midline areas or not providing good information. Mom looks and sounds exactly like Mom, but the sensation of her presence is lost. She seems somehow unreal.
The classic delusion of identification is called Capgras syndrome, after the French psychiatrist Dr. Jean Marie Joseph Capgras, who with Dr. Jean Reboul-Lachaux described in 1923 the case of a 53-year-old patient “who transformed everyone in her entourage, even those closest to her, such as her husband and daughter, into various and numerous doubles.”
In an analysis of such cases published in January in the journal Neurology, Dr. Orrin Devinsky, a neurologist at New York University, documented that people with the delusion typically have more damage to their right hemisphere than their left. Linear reasoning and language tend to be predominantly left-hemisphere functions, while holistic judgments — of intonation, of emphasis — tend to be processed more in the right. Dr. Devinsky argues that when people lack a familiar emotional glow in the company of a parent or loved one, the left hemisphere, unchecked by a damaged right, resolves the conflict with its categorical logic. The person must be an impostor.
This reminds me of that marvelous Virginia Woolf quote, in which she described the self as our sole “theme, recurring, half remembered, half foreseen.” The quote captures the mysterious nature of identity, emerging from some alchemical concoction of memory, emotion and sensation. The self feels like a singular thing – I am me – and yet it comes from no single brain area and depends on a vast network of neurons, distributed across the brain. This means that we are not a place: we are a process. As Daniel Dennett wrote, our mind is made up “of multiple channels in which specialist circuits try, in parallel pandemoniums, to do their various things, creating Multiple Drafts as they go.”
What subjects like Adam demonstrate is the fragility of the self. It’s impossible for me to imagine reality from a perspective other than my own – I am the sole perciever of all my perceptions. And yet, and yet…All it takes is a traumatic blow to the head and that delicate ghost disappears. I am suddenly someone else, convinced that my mother is a fake. (If you’d like to learn more about the Capgras delusion, I highly recommend The Echo Maker, by Richard Powers.)
Given the fundamental role of the self in human experience, it’s sobering how little we know about it. (The fact that we call it an emergent property is a sign that nobody really understands what the self is or where it comes from.) For the most part, we’re forced to marvel at its effects via attention, as the self chooses which sensations to pay attention to. These sensory cells then show increased sensitivity and enhanced firing, making them more likely to enter the narrow stream of consciousness. (This is known as selective attention or executive attention. Here’s an excellent review of the subject.) Think, for a moment, about how profoundly strange this is: the self, a fragile figment produced by all these different mental processes, is causing very real changes in neural activity. An emergent property is altering the electrical cells from which it emerged. (Douglas Hofstadter has always been very eloquent on this paradox.) It’s as if the ghost is controlling the machine.