The neural association between awareness of the self and of others: A brain imaging study of anosognosia and social cognition in early Alzheimer’s disease

Abstract

AbstractBackgroundA major proportion of patients with Alzheimer’s disease (AD) shows disorders of awareness in the early stages of disease that manifest as lack of/limited self‐awareness of their own cognitive deficits (anosognosia). Additionally, social awareness, i.e. aspects of social cognition, might also be impaired and reflect negatively on the patient’s capacity for self‐appraisal. The present study intends to explain the behavioural, brain structural and functional relationship between the presence of anosognosia and alterations in emotion and intention attribution in early‐AD, to understand the interaction between self/others awareness in the early stages of the disease.MethodsTwenty‐nine early‐AD individuals underwent neuropsychological assessment to detect the presence of anosognosia and alterations in proxies of affective ToM. Additionally, T1‐weighted structural and resting‐state functional MRI scans were acquired and pre‐processed using the Statistical Parametric Mapping (SPM) 12 software. An independent component analysis (ICA) was performed at a group level to isolate and reconstruct four intrinsic connectivity large‐scale brain networks, namely fronto‐parietal, salience, and anterior and posterior default mode networks (DMN). Non‐parametric partial correlations were performed between the neuropsychological proxies of self‐other awareness. Functional and voxel‐based morphometry multiple regression outcome maps of anosognosia and ToM were visually overlapped and brain‐masks were devised to show statistical maps of the intersecting regions.ResultsA significant negative correlation was found between cognitive outcomes of anosognosia with emotion recognition (ρ= ‐.549, p=.004) and Theory of Mind (ρ=‐.671, p=.001). There were significant brain structure intersections between anosognosia and Theory of Mind in relation to grey matter reduction in the right anterior cingulate cortex (ACC) (BA24/32) and left caudate. Anosognosia/ToM functional maps showed only visual intersections of connectivity between the anterior DMN and the inferior occipital gyrus and precentral gyrus (FWE<0.05).ConclusionThere seems to be an association between self and others awareness in early‐AD patients and its impairment appears to be underpinned by loss of neural tissue in the right ACC and subcortical regions. Similarly, the DMN seems to interact with specific occipito‐frontal regions, where visual information and mirror system dynamics might provide valuable resources to achieve self to other awareness in the presence of a neurodegenerative disease such AD.