Loss of insight in own s cognitive abilities can be a feature of a wide range of neurological disorders and can be relevant for clinical outcomes and rehabilitation effectiveness. Furthermore, recent research has shown that changes in metacognition can also characterize healthy aging and interfere with everyday life activity, increasing the incidence of a set of behaviours affecting health and decision making. Considering the subjective nature of self-awareness and the lack of consensus on assessment instruments to measure metacognitive abilities, it is important to elucidate the neuroarchitecture of metacognitive awareness and identify biomarkers of metacognitive functions. The current thesis explores this topic through four articles. According to the Cognitive Awareness Model (CAM), different type of self-awareness impairments depends on different profiles of neurocognitive dysfunctions, such as mnemonic and executive anosognosia. The former is discussed in Article 1, which focuses on mechanisms underlying impaired self-awareness in Alzheimer s disease. Specifically, the evidence suggests that Alzheimer s patients rely on outdated information about the self and are unable to consolidate new information as consequence of anterograde and retrograde amnesia. Moreover, neuroimaging findings show that fronto-cingulate and temporal degeneration are implicated in self-awareness impairments. Article 2 focused instead on neural mechanisms underlying executive anosognosia. A systematic review of event-related potential studies investigating self-monitoring in neurological disorders was conducted to understand the contribution of different brain structures to error monitoring. Specifically, the study focused on the error-related negativity (ERN) and the error positivity (Pe), which index error detection and error awareness, respectively. The findings suggest the presence of domain-general processing of error detection relying on cingulo-opercular areas and basal ganglia, but it was also hypothesized that lesions outside the fronto-basal monitoring network may lead to domain-specific deficits. To test the domain- specificity hypothesis, an event-related potential study was conducted (Article 3). A group of young and older adults completed a perceptual and a memory flanker task and the findings demonstrated that it is possible to differentiate self-monitoring processes across cognitive domains. Moreover, Pe findings demonstrated a global decline of error awareness in aging. Interestingly, in older adults only, within-task increase in Pe was specific to the memory domain, suggesting the presence of learning effects for memory but not for perceptual decisions. It was hypothesized that error awareness impairments may be associated with sensory decline in aging. Thus, Article 4 investigated the association between Pe and stimulus-locked potentials in young and older adults during memory flanker task performance, in order to understand the contribution of sensory or memory processes to age-related changes in error awareness. The findings showed that efficient stimulus recollection was associated with higher error awareness in both young and older adults and that reduced error awareness in older adults was associated with impairments in perceptual processing of stimuli. Overall, this work contributes to our understanding of neurocognitive processes underlying metacognitive awareness and neural correlates of different types of anosognosia and supports the multidimensional conceptualization of metacognitive awareness delineated by the CAM. The study s results offer novel insights into neural markers of metacognitive processes that can serve clinical assessment and the development of cognitive training and rehabilitation.