Self-awareness (SA) is a complex, rich and integrated phenomenon of self-knowledge, which is central to consciousness and incorporates multiple components 
. As a first approximation, one can distinguish several putative components of SA, which are hierarchically organized, and which might be partially dissociated, both functionally and neuroanatomically. Each component is in turn made up of multiple elements. The following description is meant to serve as a heuristic tool.
- Core SA is the most basic and fundamental component of SA and forms the foundation for all other components. It is grounded on the protoself, which includes “primordial feelings” of the living body ,  and a preattentive, elementary form of self-consciousness . On a moment to moment basis, Core SA generates a sense of personal agency and ownership over behavioral actions and sensory representations. Processes such as self-recognition and sentience require Core SA.
- Extended SA broadens Core SA to include an autobiographical self , , which involves an elaborate self-concept built upon a repository of autobiographical memories and representations of physical, affective and personality traits.
- Introspective SA relies on higher-order executive, attentional and metacognitive functions, which enable introspection, the ability to perform a more or less controlled reflection on one's own mental states, behaviors, and their consequences. Supported by memory and learning, introspective SA allows for the development of accurate knowledge about one's self, a capacity critical for efficient navigation of the social world , .
The study of the neural basis of SA has grown significantly over the past two decades 
. Several recent theoretical frameworks produced partially overlapping hypotheses regarding the specific neural substrates of SA or various components of SA. One class of hypotheses emphasizes specific brain regions, which would play a central role in essential components of SA 
, . Another class of hypotheses focuses on more distributed cortico-cortical and/or subcortical-cortical networks 
Here we concentrate on the first class of hypotheses. Four main anatomical targets have been proposed based on a variety of neuroimaging findings: the insula, ACC, mPFC, and brainstem nuclei.
The insular cortex
has been proposed as the critical substrate underlying SA in humans, necessary for interoceptive awareness 
and more generally for creating the “sentient self” or all of “human awareness” 
. On this hypothesis, the insula (especially the anterior insula) is presumed to represent the essential substrate for all components of SA (Core, Extended and Introspective).
has been implicated in functional neuroimaging studies of interoceptive and emotional awareness 
, facial self-recognition 
, and more generally in the integration of our conscious experience 
. Moreover ACC activity is closely linked to the conscious monitoring of conflict 
, and to the monitoring of self-related information underlying introspection 
. Neuropsychological studies of patients with bilateral ACC damage provide evidence for the role of the ACC in emotion, motivation, and attention 
. When ACC damage is combined with damage to the adjacent supplementary motor area, patients can manifest a profound state of akinetic mutism 
. Based on these findings, the ACC would play an important role in some aspects of both Core SA and Introspective SA.
has been consistently implicated in self-referential processing 
. In functional imaging and lesion studies, the mPFC has also been associated with the autobiographical self 
, self-reflective thought 
, and self-awareness and insight 
, as well as with the projection of the self into the future 
, and more generally with theory of mind 
. Significant changes in personality have been consistently reported in patients with bilateral lesions to the ventral portions of the mPFC (vmPFC) 
. Besides personality changes, patients with lesions to the mPFC have impaired self-regulation in social settings, such as sharing too much personal information with a stranger 
. Thus the mPFC would play a critical role in Extended SA and Introspective SA.
Finally, a specific set of nuclei in the brainstem
, including the nucleus tractus solitarius, parabrachial nucleus, and the nuclei that compose the periacquaductal gray, has been hypothesized as the neural basis for the “primordial feelings” of the living body, an essential contributor to Core SA that sets the foundation for both Extended and Introspective forms of SA 
. Of note, these nuclei are not those belonging to the ascending reticular activating system, which traditionally have been related to other aspects of consciousness, namely the processes of wakefulness and attention 
In this study, we assessed SA in a rare neurological patient, R (referred to as ‘Roger’ in previous publications), who has extensive bilateral damage to the insula, ACC and mPFC 
(, ). R's case presented a unique opportunity to: 1) evaluate the critical role of the insula, ACC and mPFC in SA, and 2) assess the profile of SA at multiple levels in a single patient using a broad array of tasks. We reasoned that if any of the structures that are damaged in this patient are indeed critical for the different aspects of SA implicated by the hypotheses reviewed above – i.e., insula, ACC, mPFC - the patient should show clear disruptions of the corresponding functions. Conversely, if these structures are not critical, R should show largely preserved SA.
T1-weighted MRI scans of R's lesion.