What's Happening in the Brain
Self awareness is classically described as a function of the frontal lobes. We know that because people who have localized damage to their frontal lobes (say from a car accident, bullet, tumor or blood vessel problem) characteristically can lose insight into their sense of who they are, and of what they are capable. This is a deep area of inquiry, and the neurobiology of self awareness has been well summarized in the paper by DT Stuss and V Anderson. The frontal lobes and theory of mind: developmental concepts from adult focal lesion research. Brain Cogn. 2004;55:69-83.
Frontal lobe impairment was classically seen as a late sign of Alzheimer's disease , but thinking about this has changed in two ways. Now that there is better testing of the frontal lobes, we see that there is involvement early. Studies suggest that early on, the brain is able to compensate for damage in the frontal lobes, but the ability to compensate becomes less as the disease progresses. This is an important insight, because it suggests that strategies to treat Alzheimer's disease need not just focus on counteracting the disease process, but can also enhance the repair process.
This issue is explored in considerable detail in the chapter on 'executive function' by Sarah Voss and Roger Bullock, of the book Trial Designs and Outcomes in Dementia Therapeutic Research, published in London in 2005 by Taylor & Francis, 2005, and edited Kenneth Rockwood and Serge Gauthier.