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Table 3 Summary of functional MRI studies

From: Neuroimaging advances regarding subjective cognitive decline in preclinical Alzheimer’s disease

Authors Definition of SCD Modality Design Sample
(mean age ± SD)
Main findings
Dummas et al. (2013) [145] Endorsed more than 20% of the items on the complaint inventory Task-fMRI Cross-sectional NC: n = 11 (56.8 ± 1.9)
SCD: n = 12 (57.1 ± 2.3)
SCD had increased activations in middle frontal gyrus, precuneus and cingulate gyrus compared to NC.
Erk et al. (2011) [146] Memory clinic consultation Task-fMRI Cross-sectional NC: n = 20 (66.8 ± 5.4)
SCD: n = 19 (68.4 ± 5.7)
SCD was associated with a reduction in right hippocampal activation during episodic memory recall in the absence of performance deficits and increased activation of the right dorsolateral prefrontal cortex.
Rodda et al. (2009) [147] Self-perceived memory difficulties persistent and severe enough to seek advice despite normal cognition Task-fMRI Cross-sectional NC: n = 10 (68.0 ± 13.5)
SCD: n = 10 (64.2 ± 5.6)
SCD exhibited increased activation in left during the divided attention task.
Hu et al. (2017) [150] Criteria by SCD-I Task-fMRI Cross-sectional NC: n = 24 (66.5 ± 7.2)
SCD: n = 20 (68.3 ± 7.9)
Subtle neuronal network disruptions in SCD.
Hayes et al. (2017) [149] Worrisome decline in memory Task-fMRI Cross-sectional NC: n = 41 (67.5 ± 9.1)
SCD: n = 23 (68.6 ± 8.2)
SCD showed a more negative subsequent memory effects in the default mode network.
Dillen et al. (2017) [138] A cut-off value of≥25 on the memory complaint questionnaire but average scores on neuropsychological tests rs-fMRI Cross-sectional NC: n = 25 (62.4 ± 7.0)
SCD: n = 28 (65.8 ± 7.8)
Prodromal AD: n = 25 (70.8 ± 6.2)
SCD showed decreased connectivity between DMN and hippocampus.
Hafkemeijer et al. (2013) [73] Memory complaints but normal cognition T1 MRI and rs-fMRI Cross-sectional NC: n = 29 (71.3 ± 3.4)
SCD: n = 25 (71.4 ± 9.2)
SMC showed increased FC in the default mode network.
Sun et al. (2016) [122] Self-reported persistent decline in memory compared with a previous state but normal cognition T1 MRI and rs-fMRI Cross-sectional NC: n = 61 (64.1 ± 8.6)
SCD: n = 25 (65.5 ± 6.1)
SCD had higher ALFF values in the left inferior parietal lobule and right middle occipital gyrus than control subjects, which were correlated with verbal episodic memory scores.
Verfaillie et al. (2018) [128] 1 binary question rs-fMRI Longitudinal (one year) Baseline NC: n = 56 (64 ± 5)
Baseline SCD: n = 68 (64 ± 5)
Follow-up NC: n = 29 (65 ± 6)
Follow-up SCD: n = 30 (65 ± 6)
SCD showed increased pDMN–MTMS connectivity. Higher connectivity between MTMS and the rest of brain was associated with better baseline immediate memory, attention, and global cognition. Higher
MTMS and pDMN–MTMS connectivity were associated with lower immediate memory over time.
Wang et al. (2013) [139] Endorsed more
than 20% of the items on the Cognitive Complaint Index
rs-fMRI Cross-sectional NC: n = 16 (70.7 ± 6.0)
SCD: n = 23 (70.1 ± 7.3)
MCI: n = 18 (73.7 ± 9.1)
SCD showed decreased DMN connectivity in the right hippocampus compared to NC and higher connectivity compared to MCI.
Yasuno et al. (2015) [113] Reisberg criteria rs-fMRI Cross-sectional NC: n = 30 (72.2 ± 4.8)
SCD: n = 23 (69.6 ± 8.0)
SCD showed reduced FC in cortical midline structures
Cavedo et al. (2018) subjective memory complaints 18F-florbetapir-PET
FDG-PET
MRI
Cross-sectional Women: n=201 (76.02±3.24)
Men: n = 117(76.05±3.85)
Men had lower resting-state FC.
Chiesa et al., (2019) [140] 2 binary questions rs-fMRI Cross-sectional ApoE ɛ4+: 44 (75.6 ± 3.5)
ApoE ɛ4-: 180 (75.5 ± 3.4)
ApoE ɛ4+ showed slower increase in FC in frontal lobes.
Dillen et al., (2016) [136] Structural questionnaire rs-fMRI Cross-sectional NC: n = 25 (62.4 ± 7.0)
SCD: n = 27 (65.7 ± 7.9)
AD: n = 24 (71.0 ± 6.2)
Higher FC from RSC to frontal cortex in SCD.
Dong et al., (2018) [137] Memory clinic consultation rs-fMRI Cross-sectional NC: n = 39 (82.89 ± 4.13)
SCD: n = 39 (83 ± 4.43)
Lower aFCS in SCD.
Viviano et al., (2019) [115] 2 binary questions rs-fMRI Cross-sectional NC: n = 48 (66.96 ± 8.79)
SCD: n = 35 (68.51 ± 7.66)
SCD showed lower average FC.
Eulate el al., (2017) [163] Memory clinic consultation ASL Cross-sectional NC: n = 32 (72.3 ± 5.6)
SCD: n = 28 (67.3 ± 7.8)
MCI: n = 34 (73.7 ± 7.5)
AD: n = 21 (75.8 ± 6.2)
No differences in CBF between SCD and HC.
Hays et al., (2018) [162] Memory clinic consultation ASL Cross-sectional NC: n = 35 (73 ± 6.25)
SCD: n = 35 (72.54 ± 5.07)
SCD showed negative associations between verbal memory and CBF.
Leeuwis et a., (2017) [164] Memory clinic consultation ASL Cross-sectional SCD: n = 143 (56.69 ± 8.69)
MCI: n = 95 (65.24 ± 7.28)
AD: n = 161 (65.93 ± 7.04)
No correlation between CBF and cognition.
Yang et al., (2019) [165] SCD-I Working Group rs-fMRI Cross-sectional NC: n = 55 (63.41 ± 7.97)
SCD: n = 43 (65.09 ± 8.66)
aMCI: n = 52 (68.06 ± 9.32)
AD: n = 44 (70.98 ± 10.02)
SCD showed lower fALFF.
  1. FDG 18F-Fluorodeoxyglucose, SCD Subjective cognitive decline, AD Alzheimer’s disease, MCI Mild cognitive impairment, aMCI Amnestic MCI, NC Normal control, PET Positron emission tomography, MRI Magnetic resonance imaging, fMRI Functional MRI, rs-fMRI Resting-state fMRI, MTL Medial temporal lobe, ALFF Amplitude of low-frequency fluctuations, fALFF Fractional ALFF, DMN Default mode network, pDMN Posterior DMN. SMC: Subjective memory complaints, MTMs Medial temporal memory system, RSN Resting-state networks, VIS Visual, CCI Cognitive complaint index, ASL Arterial spin labeling, CBF Cerebral blood flow, SCD-I Subjective Cognitive Decline Initiative, FC Functional connectivity, ApoE Apolipoprotein E