Excerpt from The Man Who Wasn't There by Anil Ananthaswamy, plus links to reviews, author biography & more

The search for the self is also well served by thinking of it in terms of two categories: the "self-as-object" and the "self-as-subject." It turns out that some aspects of the self are objects to itself. For instance, if you were to say, "I am happy"—the feeling of happiness, which is part of your sense of self at that moment, belongs to the self-as-object category. You are aware of it as a state of your being. But the "I" that feels happy—the one that is aware of its own happiness—that's the more slippery, elusive self-as-subject. The same "I" could also be depressed, ecstatic, and anything in between.

With this distinction in mind, if you take Laureys's studies, which show that in healthy subjects the frontoparietal network activity constantly switches back and forth from internal to external awareness, what seems to be changing is the content of one's consciousness: from awareness of external stimuli to awareness of aspects of one's self. When you are self-aware, in that you are conscious of your own body, your memories, and your life story, aspects of the self become the contents of consciousness. These comprise the self-as-object.

It's possible that parts of this self-as-object are not being experienced vividly in Cotard's syndrome. Whatever it is that tags objects in our consciousness as mine or not-mine, self or not-self, may be malfunctioning (we'll see in coming chapters some mechanisms that could be behind such tagging). In Graham's case, the mineness or vividness that is usually attributed to, say, one's body and/or emotions was maybe lacking. And the resulting untenable belief that he was brain dead entered his conscious awareness unchallenged, given his underactive, low-functioning lateral frontal lobes.

But regardless of what one is aware of, isn't there someone who is always the subject of the experience? Even if you are completely absorbed in something external, say, a melancholic violin solo—and the contents of your consciousness are devoid any self-related information, whether of your body or worries about your job—does the feeling that you are having that experience ever go away?

To help us get closer to some answers, we can turn to insights of people suffering from various perturbations of the self, which serve as windows to the self. Each such neuropsychological disorder illuminates some sliver of the self, one that has been disturbed by the disorder, resulting at times in a devastating illness.

These words from Lara Jefferson's These Are My Sisters: A Journal from the Inside of Insanity leave us in no doubt of the damage wrought to the self in a schizophrenic person: "Something has happened to me—I do not know what. All that was my former self has crumbled and fallen together and a creature has emerged of whom I know nothing. She is a stranger to me. . . . She is not real—she is not I . . . she is I—and because I still have myself on my hands, even if I am a maniac, I must deal with me somehow."

But in the devastation are clues to what makes us who we are. These maladies are to the study of the self what brain lesions are to study of the brain: They are cracks in the façade of the self that let us examine an otherwise almost impenetrable, ongoing, unceasing neural process. And while what follows in the coming chapters is not an exhaustive list of all neuropsychological conditions that disturb the self, I have chosen conditions that satisfied at least two criteria: first, they were amenable to studying some distinct aspect of the self, and second, there is significant ongoing science that specifically addresses these conditions from the perspective of the self.

In Alzheimer's we get a sense of one's story unraveling. If you can't answer the question "Who am I?" with declarative statements ("I am Richard," "I am a retired professor," and so on), either because your memory is failing you or the brain regions that let you reflect upon these characteristics are damaged, have you lost your sense of self? If so, have you lost all of it, or part of it? What if, despite the cognitive disintegration of your coherent story—what some call the narrative or autobiographical self—other aspects of you still functioned?

Excerpted from The Man Who Wasn't There by Anil Ananthaswamy. Copyright © 2015 by Anil Ananthaswamy. Excerpted by permission of Dutton. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.