Amnestic Mild Cognitive Impairment Is Associated With Frequency-Specific Brain Network Alterations in Temporal Poles

Abstract

There is general agreement that the neuropathological processes leading to Alzheimer’s disease (AD) begin decades before the clinical onset. In order to detect early topological changes, we applied functional connectivity and network analysis to magnetoencephalographic (MEG) data obtained from 16 patients with amnestic Mild Cognitive Impairment (aMCI), a prodromal stage of AD, and 16 matched healthy control (HCs). Significant differences between the two groups were found in the theta band, which is associated with memory processes, in both temporal poles (TPs). In aMCI, the degree and betweenness centrality (BC) were lower in the left superior TP, whereas in the right middle TP the BC was higher. A statistically significant negative linear correlation was found between the BC of the left superior TP and a delayed recall score, a sensitive marker of the “hippocampal memory” deficit in early AD. Our results suggest that the TPs, which are involved early in AD pathology and belong to the memory circuitry, have an altered role in the functional network in aMCI.

Disrupted Patterns of Rich-Club and Diverse-Club Organizations in Subjective Cognitive Decline and Amnestic Mild Cognitive Impairment

“…Although there was no significant difference between the SCD group and HC group, the SCD group also had the same trend as the aMCI group in the small-world parameters (σ), normalized clustering coefficient (γ), and characteristic path length (L p ). Jacini et al (2018) applied functional connectivity to MEG data and found no global topological changes in aMCI, which was not consistent with our results. The inconsistent results may be due to patient heterogeneity or the nature that rs-fMRI and diffusion tensor imaging were more sensitive to capture changes of the global network than MEG (Jacini et al, 2018).…”

“…Jacini et al (2018) applied functional connectivity to MEG data and found no global topological changes in aMCI, which was not consistent with our results. The inconsistent results may be due to patient heterogeneity or the nature that rs-fMRI and diffusion tensor imaging were more sensitive to capture changes of the global network than MEG (Jacini et al, 2018). The small-world networks were featured by a high representation of strongly interconnected networks, equipped with higher γ and lower L p (Wang et al, 2013).…”

Clinical connectome fingerprints of cognitive decline

“…Examining functional connectivity in the human brain offers unique insights on how integration and segregation of information relates to human behavior and how this organization may be altered in diseases (6). Indeed, considerable evidence has confirmed that anomalies in either the co-activations, the synchronization and/or the topology of the brain network are likely occurring in MCI (7,8).…”

Wide temporal horns are associated with cognitive dysfunction, as well as impaired gait and incontinence

“…Decreased volume of the hippocampal formation and increased width of the TH have been related to age in a healthy study population and to mild cognitive impairment (MCI) [44][45][46] . Future studies on standardized measures of the width of the TH would be helpful to differentiate between pathology and normal ageing.…”