We showed previously that in the current sample of healthy adults, age has a negative effect on performance in the Trail Making Test (TMT-A: r = .51; p < .001, TMT-B: r = .55, p < .001; see30). Initial exploratory correlations between spectral power and cognitive performance revealed different linear trends across different age groups. To further investigate this, we ran multiple linear regressions, using age, slow wave power and their interaction as predictors and performance on the Trail Making Test as the dependent variable. IAF was initially entered as a covariate but it did not reduce AIC46 by ≥2, therefore the more parsimonious models were selected. Results from F-tests comparing the full with reduced models, excluding the effect under consideration, showed no significant contribution of IAF.
