Neural correlates of altered insight in frontotemporal dementia: a systematic review

Abstract

Altered insight into disease or specific symptoms is a prominent clinical feature of frontotemporal dementia (FTD). Understanding the neural bases of insight is crucial to help improve FTD diagnosis, classification and management. A systematic review to explore the neural correlates of altered insight in FTD and associated syndromes was conducted. Insight was fractionated to examine whether altered insight into different neuropsychological/behavioural objects is underpinned by different or compatible neural correlates. 6 databases (Medline, Embase, PsycINFO, Web of Science, BIOSIS and ProQuest Dissertations & Theses Global) were interrogated between 1980 and August 2019. 15 relevant papers were found out of 660 titles screened. The studies included suggest that different objects of altered insight are associated with distinctive brain areas in FTD. For example, disease unawareness appears to predominantly correlate with right frontal involvement. In contrast, altered insight into social cognition potentially involves, in addition to frontal areas, the temporal gyrus, insula, parahippocampus and amygdala. Impaired insight into memory problems appears to be related to the frontal lobes, postcentral gyrus, parietal cortex and posterior cingulate. These results reflect to a certain extent those observed in other neurodegenerative conditions like Alzheimer's disease (AD) and also other brain disorders. Nevertheless, they should be cautiously interpreted due to variability in the methodological aspects used to reach those conclusions. Future work should triangulate different insight assessment approaches and brain imaging techniques to increase the understanding of this highly relevant clinical phenomenon in dementia.

Keywords: Frontotemporal dementia; Insight; Neural correlates.

Fig. 1

PRISMA Flow Diagram.

Fig. 2

Brain areas involved in altered insight into different objects in patients with frontotemporal dementia and associated syndromes MRI = magnetic resonance imaging; PET = positron emission tomography; SPECT = single-photon emission computed tomography; CT = computed axial tomography This figure was created with the Montreal Neurological Institute (MNI) template. The coloured figures represent spatial approximations only (see Tables 2 and 3 for more accurate details). Garcia-Cordero et al. (2016), Levy et al. (2018), McMurtray et al. (2006), Rosen et al. (2010), Shany-Ur et al. (2014) and Sollberger et al. (2014) were not illustrated in this figure.