Age-related changes in “cortical” 1/f dynamics are explained by cardiac activity

The power of electrophysiologically measured cortical activity decays 1/fX. The slope of this decay (i.e. the spectral exponent) is modulated by various factors such as age, cognitive states or psychiatric/neurological disorders. Interestingly, a mostly parallel line of research has shown similar effects for the spectral exponent in the electrocardiogram (ECG). This raises the question whether these bodywide changes in spectral exponents are independent or if the “cortically” measured decay in power is explained by cardiac activity captured by cortical sensors (via volume conduction). Focusing on well-established age-related changes in spectral exponents, we analyzed a total of 1282 recordings of magnetoencephalography (MEG) resting state measurements with concurrent ECG in an age-diverse sample. We show that age-related changes of the spectral exponent of neural power spectra are largely explained by cardiac activity. Our results raise concerns when interpreting aperiodic activity as “cortical“ in absence of ECG recordings.