Anosognosia, disordered awareness of cognitive and behavioral
deficits, is a striking and common symptom of Alzheimer's disease
(AD), yet its etiology, clinical correlates, and prognostic value are
unclear. Historically, disordered awareness has been a conceptually
challenging phenomenon, evidenced by the numerous and diverse theories
that aim to explain the manner in which this syndrome arises. We review
many of these theories, focusing on the neuroanatomic substrates of
awareness, and highlighting the potential roles of critical regions such
as the right prefrontal and parietal cortices in enabling self-awareness.
We then address methodological limitations such as use of subjective
measurement tools that likely contribute to the conceptual ambiguity
surrounding anosognosia. We argue that metacognitive techniques used in
healthy adults, such as the Feeling of Knowing task, offer models
for dissecting awareness into clear and identifiable cognitive components
in patients with AD. We critique several studies that have pioneered such
tasks in AD, and offer guidelines for future implementation of such
methods. A final goal of this review is to advocate for a multidimensional
approach to studying metacognitive skills that will facilitate the
objective investigation of deficit awareness as it relates to a variety of
disease variables such as prognosis, neuropsychological profile,
neuropathological distribution, psychiatric symptoms, and clinical course.
(JINS, 2005, 11, 910–919.)