Table 5.
Overview of brain imaging studies and their results in Alzheimer's disease for different modalities.
| Changes in AD imaging compared to healthy controls | Imaging modality | Reference for evidence | Contradicting evidence | |
|---|---|---|---|---|
| Global connectome changes | Decreased global efficiency/longer characteristic path length | EEG | (Stam et al., 2007; de Haan et al., 2009) | |
| MEG | (Stam et al., 2009) | |||
| fMRI | Amnestic MCI (Minati et al., 2014); AD (Sanz-Arigita et al., 2010; Zhao et al., 2012) | Similar characteristic path length as controls (Supekar et al., 2008) | ||
| sMRI | (Lo et al., 2010; Reijmer et al., 2013; Daianu et al., 2015; Zhao et al., 2017) (not significant); (He et al., 2008; Yao et al., 2010) | |||
| Decreased averaged local efficiency | sMRI | (Reijmer et al., 2013) | Increased averaged local efficiency in fMRI (Zhao et al., 2012) | |
| Decreased global clustering | EEG | (de Haan et al., 2009) | ||
| MEG | (Stam et al., 2009) | Preserved clustering coefficient in EEG (Stam et al., 2007) | ||
| fMRI | Amnestic MCI (Minati et al., 2014); AD (Supekar et al., 2008; Dai et al., 2019) | Increased global clustering in fMRI (Zhao et al., 2012); unchanged global clustering in fMRI (Sanz-Arigita et al., 2010) | ||
| sMRI | (Reijmer et al., 2013; Pereira et al., 2016; Dai et al., 2019) (not significant) | Increased clustering coefficient in structural MRI (He et al., 2008; Yao et al., 2010); | ||
| Decreased network robustness | MEG | (de Haan et al., 2012) | ||
| Altered modular structure | fMRI | Amnestic MCI (Minati et al., 2014); AD (Chen et al., 2013; Dai et al., 2019) | ||
| sMRI | (Pereira et al., 2016; Dai et al., 2019) | |||
| Rich club organization affected | sMRI | (Pereira et al., 2016; Yan et al., 2018; Dai et al., 2019) | ||
| Network changes | DMN is attacked by AD | fMRI | (Çiftçi, 2011; Hahn et al., 2013; Dai et al., 2014, 2019; Bernard et al., 2015; Chen et al., 2016; Cope et al., 2018) | Increased local efficiency in the DMN in fMRI (Zhao et al., 2012) |
| sMRI | (Hahn et al., 2013; Zhao et al., 2017; Dai et al., 2019) | |||
| The core of the network is most affected | sMRI, MEG, and fMRI | (Guillon et al., 2019) | Predominantly low-degree regions outside the core loose connectivity in structural MRI (Daianu et al., 2015) | |
| Increased connectivity for sensorimotor system | sMRI, MEG, and fMRI | (Guillon et al., 2019) | ||
| Regional connectome changes | Decreased connectivity in the insula | fMRI | (Chen et al., 2013) | |
| Decreased connectivity in the posteromedial cortex | fMRI | (Xia et al., 2014) | ||
| Decreased connectivity in the medial temporal cortex | fMRI | (Burggren and Brown, 2014) | ||
| Decreased connectivity in the amygdala | fMRI | (Yao et al., 2013; Wang et al., 2016) | ||
| Decreased connectivity in the parahippocampal area | sMRI | (Solodkin et al., 2013) | ||
| Decreased connectivity in frontal regions | sMRI | (Lo et al., 2010) | Increased connectivity within frontal areas in fMRI (Supekar et al., 2008) | |
| Disconnection of the precuneus, parietal and temporal areas | fMRI | Amnestic MC (Minati et al., 2014) | ||
| Reduced local clustering for the hippocampus | fMRI | (Supekar et al., 2008) | ||
| Decreased connectivity within the temporal lobe | fMRI | (Supekar et al., 2008) | ||
| Regional atrophy | Atrophy in the hippocampus | sMRI | Mild dementia stage of AD (Bosscher and Scheltens, 2002; van der Flier et al., 2005); amnestic MCI (Shi et al., 2009) | |
| Atrophy and thinning of the entorhinal cortex | sMRI | (Bobinski et al., 1999; Dickerson et al., 2001; Teipel et al., 2006; Velayudhan et al., 2013; Blanc et al., 2015) | ||
| Reduction of amygdala volume | sMRI | (Whitwell et al., 2005; Barnes et al., 2006) | ||
| Volume loss in the thalamus | sMRI | (Callen et al., 2001; Yi et al., 2016) | ||
| Tau PET | Reduction in caudate nucleus volume | sMRI | (Rombouts et al., 2000; Madsen et al., 2010) | |
| Atrophy in the nucleus accumbens | sMRI | (Liu et al., 2010; Yi et al., 2016) | ||
| Global neocortical Tau binding increased | 18F-AV-1451 | (Cho et al., 2016; Pontecorvo et al., 2019) | ||
| Early Braak stage Tau binding increased | 18F-AV-1451, 11C-PBB3 | Entorhinal cortex in MCI (Cho et al., 2016); Precuneus and lateral parietal in inherited AD (Gordon et al., 2019); lateral and medial frontal cortex in AD (Harrison et al., 2019); orbitofrontal cortex in AD (11C-PBB3) (Kitamura et al., 2018); middle to high Braak stages (Schöll et al., 2016) | Increased Tau binding in older healthy controls' temporal and retrosplenial cortex (Harrison et al., 2019) | |
| Tau in network hubs | 18F-AV-1451, 11C-PBB3 | (Cope et al., 2018; Kitamura et al., 2018) | Low consistency between atrophy and Tau deposition in atypical AD (18F-AV-1451) (Sintini et al., 2019) | |
| Abeta PET | Global Abeta binding increased | 18F-AV-45 (Florbetapir) | Visual rating (Clark et al., 2011; de Wilde et al., 2018) | |
| Early Braak stage Abeta binding increased. | Florbetaben (18F), 11C-PIB | Inferior frontal cortex and precuneus (Alongi et al., 2019); striatum in hereditary PSEN1 patients (Klunk et al., 2007) and PSEN1/APP patients (Villemagne et al., 2009); (Murray et al., 2015) | Middle to high Braak stages in HC, but age-related and associated with ApoE: with 11C-PIB (Jack et al., 2014), meta-analysis (Jansen et al., 2015); medial temporal lobe in HC (Song et al., 2015) | |
| Abeta binding increased in DMN | 18F-AV-45 (Florbetapir) | Hubs of DMN including hippocampus (Chang et al., 2015) | ||
| Glucose PET | (left) temporoparietal hypometabolism | 18FDG | Left precuneus, posterior cingulate and superior parietal cortex in MCI-to-AD converters (Morbelli et al., 2010), bilaterally in Fukai et al. (2018), and ApoE ε4 carriers (Langbaum et al., 2010); temporal, angular and posterior cingular areas (Ou et al., 2019); frontal, posterior temporal, and parietal cortex (Meltzer et al., 1996) | Age-related temporal hypometabolism in HC (Jack et al., 2014); low sensitivity in a meta-analysis for differentiation of MCI converters (Smailagic et al., 2015) |
| Hypometabolism associated with Tau | 18FDG | Hypometabolism only in the presence of Abeta in Tau-positive regions (Adams et al., 2018) | Hypermetabolism caused by low Tau burden in the absence of Abeta (Adams et al., 2018) | |
EEG, electroencephalography; MEG, magnetoencephalography; fMRI/sMRI, functional/structural magnetic resonance imaging; PET, positron emission tomography; DMN, default mode network; AD, Alzheimer's Disease; MCI, mild cognitive impairment.