Neural correlates of impaired cognitive processes underlying self-unawareness in Alzheimer's disease

Resting-state networks and anosognosia in Alzheimer’s disease

“…ACC is a major hub of the SN with a key role in processing and integrating internal and external inputs for decision-making ( Seeley et al, 2007 ). As suggested by Salmon and co-authors ( Salmon et al, 2024 ), ACC activity might be involved in higher-order processes for self-referencing (related to the metacognitive awareness system in the CAM model). Our results suggest that the greater the anosognosia, the stronger the SN-related ACC functional connectivity.…”

“…Several studies demonstrated a decreased functional connectivity between the PCC and the hippocampus in anosognosic patients ( Perrotin et al, 2015 ; Vannini et al, 2017 ); in addition, PCC was also found to be implicated in implicit awareness mechanisms when using a modified Stroop emotional task ( Tondelli et al, 2022 ). Cavanna and Trimble (2006) hypothesized that self-appraisal processes were driven by PCC activity involved in retrieval and integration of mental representations, therefore, if applied to Cognitive Awareness Model (CAM) ( Agnew and Morris, 1998 ; Lenzoni et al, 2020 ), PCC may play a role in integration and comparison of current information with stored autobiographical information ( Salmon et al, 2024 ). Decreased functional connectivity was also found in MCC with the DMN component when considering both AQ-D correlation analysis and comparison between aware and unaware patients.…”

“…Interestingly, involvement of medial and lateral temporal regions was not revealed in our study. Several neuroimaging studies showed that middle temporal gyrus is implicated in autobiographical memory suggesting that this area could be a key region for the personal database in the CAM leading to “the petrification of the self” as a core feature of anosognosia in AD ( Salmon et al, 2024 ). Previous fMRI studies investigating network connectivity in anosognosia demonstrated temporal cortical connectivity involvement when using measures of memory anosognosia: Antoine et al reported disconnection within the medial temporal subsystem of the default mode network, subserving episodic memory processes, using a Memory Awareness Rating Scale ( Antoine et al, 2019 ); Valera-Bermejo et al showed that memory anosognosia scores were associated with selective lower frontotemporal connectivity and higher parietotemporal connectivity, whereas total anosognosia scores were associated with large-scale network alterations, namely reduced left-FPN expression in the left posterior cingulate, reduced right-FPN expression in the left inferior lingual gyrus and adjacent inferior occipital cortex, and increased right-FPN expression in the right anterior cingulate ( Valera-Bermejo et al, 2021 ).…”

Impaired Self-Awareness in Parkinson’s and Huntington’s Diseases: A Literature Review of Neuroimaging Correlates

“…Still, little data are available for HD patients to infer any conclusion. Studies of awareness have mainly focused on Alzheimer's Disease (AD) patients, and models of anosognosia have mainly been proposed to interpret awareness in memory and metacognitive domains [9,13,[44][45][46], suggesting that selfawareness and anosognosia rely upon different networks that are functionally correlated and support communication between an "external" source of information and "internal" personal knowledge. In the AD literature, emerging evidence suggests that awareness may rely upon an interplay between the salience network, a resting-state network known to be involved in detecting, processing, and integrating internally and externally generated salient information [31]; the default mode network, a set of interconnected brain regions that are suppressed during tasks that demand externalized attention [47]; and the frontoparietal network, a network known to be implicated in a wide range of executive functions, including working memory, performance monitoring, and planning [48,49].…”

Data_Sheet_1.docx

“…Several studies demonstrated a decreased functional connectivity between the PCC and the hippocampus in anosognosic patients (Perrotin et al, 2015;Vannini et al, 2017); in addition, PCC was also found to be implicated in implicit awareness mechanisms when using a modified Stroop emotional task (Tondelli et al, 2022). Cavanna and Trimble (2006) hypothesized that self-appraisal processes were driven by PCC activity involved in retrieval and integration of mental (Agnew and Morris, 1998;Lenzoni et al, 2020), PCC may play a role in integration and comparison of current information with stored autobiographical information (Salmon et al, 2024). Decreased functional connectivity was also found in MCC with the DMN component when considering both AQ-D correlation analysis and comparison between aware and unaware patients.…”