Table 1.

Results after qualitative synthesis.

References	Participants	CR measure	EEG measure	Number of channels	Results
Speer and Soldan (2015)	Healthy young and older adults (25:21)	A composite score of results of language tasks and education	P300b	32 scalp ActiveTwo electrodes, Biosemi	Higher CR associated with lower neural inefficiency
Gu et al. (2018)	Healthy older adults and older adults with MCI	CRIq	P300	64 scalp electrodes	Different networks used in healthy vs. aMCI groups
Amodio et al. (2017)	82 patients with liver cirrhosis	CRIq	EEG traces in P3-P4 derivation	21 Ag/AgCl electrodes	No significant relationships between CRIq and physiological parameters
Fleck et al. (2017)	90 healthy adults (M = 58.51)	A composite score of verbal IQ and education	Frequency bands: delta, theta, low alpha, high alpha, beta, gamma	129-channel HydroCel Geodesic Sensor Net	Significant decrease in resting-state coherence with aging in low-CR