The relationship between cognitive reserve and neuroplasticity in older adults

Abstract

Background: Cognitive Reserve (CR) is suggested to explain the difference between the expected impact of levels of age-related neuropathology and the real deficits which people experience. Neuroplasticity is speculated to be the neurophysiological mechanism underlying the cognition-protective effects of CR; however, this has not previously been experimentally demonstrated. Aim: To identify whether neuroplasticity mediates the relationship between CR and cognitive ability. Method: 23 healthy older adults participated in this study, which comprised 3 brain stimulation sessions: (1) continuous theta-burst stimulation (cTBS) applied to left dorsolateral prefrontal cortex, (2) cTBS applied to left motor cortex, and (3) a sham session. Resting electroencephalography (EEG) was used to calculate change in the aperiodic slope of neural power spectra (a novel measure of neuroplasticity) following cTBS. Participants were also assessed with measures of CR (lifetime of experiences; crystallised intelligence) and cognitive ability (fluid intelligence; paired associates learning). Results: We induced a neuroplasticity-like effect in both of the active cTBS conditions. This was not observed in the sham condition. We did not observe a significant relationship between neuroplasticity and CR or cognitive ability. This meant mediational analysis was not justified. Conclusions: We successfully demonstrated that analysis of the aperiodic slope is an effective means of identifying neuroplasticity with EEG. While we did not identify a significant relationship between our neuroplasticity measure and CR, we recommend further studies investigate other forms of neuroplasticity. Continued investigation of the neurophysiology underlying CR may facilitate the development of early interventions which could reduce the prevalence of age-related cognitive impairment.