The emergent relationship between temporoparietal junction and anosognosia in Alzheimer's disease

Abstract

Anosognosia and impairment of insight are characteristic features of Alzheimer's disease (AD), which can lead to delays in appropriate medical care and significant family discord. The default mode network (DMN), a distributed but highly connected network of brain regions more active during rest than during task, is integrally involved in awareness. DMN dysfunction is common in AD, and disrupted communication between memory‐related and self‐related DMN networks is associated with anosognosia in AD patients. In addition, the temporoparietal junction (TPJ) is a key region of the “social brain” and also contributes to representations of the self. The exact classification of the TPJ within the DMN is unclear, though connections between the TPJ and DMN have been highlighted in multiple avenues of research. Here we discuss the relationship between the TPJ, DMN, and AD, as well as the potential involvement of the TPJ in anosognosia in AD. We review past and present findings to raise attention to the TPJ, with a specific emphasis on neuroimaging technologies which suggest a pivotal role of the TPJ within large‐scale brain networks linked to anosognosia in AD.

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

“…In the literature, other-referential processes may produce greater response than selfappraisal within the DMPFC and in the temporoparietal junction (TPJ) (Frewen et al, 2020). The TPJ is a key region of the "social brain", it contributes to representations of the self (Lattanzio, Seames, Holden, & Buard, 2021) and it is involved in object level comparison processes (Jiang, Wang, & Wan, 2022). The different correlations between anosognosia scores and DMPFC or TPJ in the literature (Jedidi et al, 2013;Salmon et al, 2006) are consistent with a meta-analysis which found the TPJ to be J o u r n a l P r e -p r o o f involved in inferring concrete, present states (such as evaluating recent cognitive functioning), while the DMPFC was involved in inferring people's social, enduring dispositions (such as the evaluation of personality traits) (Van Overwalle, 2009).…”

Anosognosia in hoarding disorder is predicted by alterations in cognitive and inhibitory control

“…In contrast to the dynamic psychiatric model of ‘insight impairment,’ the term ‘anosognosia’ refers specifically to impaired awareness of illness and its symptoms. Pathophysiologic understanding of anosognosia has emphasized its neurobiological basis—the disruption to relevant cortical and subcortical circuits and substrates—particularly implicating right hemispheric areas, including prefrontal, temporoparietal, and insular cortex 9 – 13 .…”