According to some theories on how self-awareness arises in the brain, Patient R, a man who suffered a severe brain injury about 30 years ago, should not possess this aspect of consciousness.
In 1980, a bout of encephalitis caused by the common herpes simplex virus damaged his brain, leaving Patient R, now 57, with amnesia and unable to live on his own.
Even so, Patient R functions quite normally, said Justin Feinstein, a clinical neuropsychologist at the University of Iowa who has worked with him. "To a layperson, to meet him for the first time, you would have no idea anything is wrong with him," Feinstein said.
Feinstein and colleagues set out to test Patient R's level of self-awareness using a battery of tools that included a mirror, photos, tickling, a lemon, an onion, a personality assessment and an interview that asked profound questions like "What do you think happens after you die?" [ The Science of Death: 10 Morbid Tales ]
Their conclusion — that Patient R's self-awareness is largely intact in spite of his brain injury — indicates certain regions of the brain thought crucial for self-awareness are not.
Brain anatomy
Self-awareness is a complex concept, and neuroscientists are debating from where it arises in the brain. Some have argued that certain regions in the brain play critical roles in generating self-awareness.
The regions neuroscientists have advocated include the insular cortex, thought to play a fundamental role in all aspects of self-awareness; the anterior cingulate cortex, implicated in body and emotional awareness, as well as the ability to recognize one's own face and process one's conscious experience; and the medial prefrontal cortex, linked with processing information about oneself.
Patient R's illness destroyed nearly all of these regions of his brain. Using brain-imaging techniques, Feinstein and colleagues determined that the small patches of tissue remaining appeared defective and disconnected from the rest of the brain. [ Inside the Brain: A Journey Through Time ]
The tests
The team breaks self-awareness down into three components: an awareness of one's body and a sense of one's ability to act; autobiographical memories and a sense of one's own traits; and an ability to reflect on one's own actions, mental state and their consequences.
The first test they gave Patient R is the mirror test. The researchers sneaked a bit of black eye shadow onto R’s nose under the pretense of brushing something off his nose. When he was later shown his reflection in the mirror, the researchers watched to see if he responded to the mark on his nose.
He was also shown photos of himself throughout his life along with photos of family, familiar people and strangers and asked whether or not he could identify himself. In unaltered photos, he was 100 percent successful in identifying himself, but he had difficulty recognizing himself in photos altered to exclude everything except his own face.
"However, he never rated a picture of another person as himself," note the researchers.
R suffers from amnesia that affects memories of some experiences that occurred before his illness, and prevents him from forming new memories since, so these results suggest he was able to maintain a concept of himself even beyond his own amnesia, Feinstein said.
In another test, R's response to being tickled by himself versus by a researcher, was recorded. Tickling can be used to test self-awareness because tickling yourself doesn't feel the same as being tickled by someone else. "R was never observed laughing or displaying jerking movements during any of the self-administered tickling trials," they write.
Researchers assessed his awareness of the amount of control he exerted over a box moving around a computer screen, and had him and family members assess his personality.
An exception
R's brain injury took away his sense of smell and taste, as well as much of his memory. R partially acknowledges his memory loss, even describing himself as a "normal person with a bad memory," However, he does not admit that he cannot smell or taste.
The researchers put this to the test by blindfolding him and then offering him an onion or lemon or odorless items and asking what he smelled. With the blindfold on, he could not smell the lemon or onion. With it off, he claimed to smell them, explaining, "I guess sight makes things easier."`
Knowing one's limitations is an aspect of self-awareness, Feinstein said.
Patient R & the origin of self-awareness
Finally, in an interview the researchers assessed his capacity for introspection, asking him questions about free will, the self, emotion and other abstract concepts.
"I think what the interview reveals is clearly somebody who is not impaired in most aspects of self-awareness," Feinstein said. "If you were asking someone who was a zombie, you wouldn't get any of these sorts of answers."
The results of the assessment are clear, he and colleagues contend: Neither the insula cortex, the anterior cingulate cortex nor the medial prefrontal cortex play crucial roles in self-awareness.
Patient R's self-awareness does, however, support the theory that sets of neurons in the brain stem may provide the foundation for consciousness and the sense of self. This part of R's brain is undamaged. The team also suggests other parts of the brain, the thalamus and the posteromedial cortex, play a role in self-awareness.
"The brain more than likely doesn't have a single region that is devoted to self awareness, but rather, the complex phenomenon likely emerges from much more distributed interactions between multiple brain regions," Feinstein said. "I think it is important to emphasize that the study of self-awareness in the brain is really in its early stages."
The research was published today (Aug. 22) in the journal PLoS ONE.
Follow LiveScience writer Wynne Parry on Twitter @Wynne_Parry or LiveScience @livescience. We're also on Facebook & Google+.
